A glass ampulla, which bulges up inside at the bottom like a cone, is

covered on the lower part of the outside with lute in the way explained

above, and into it is put silver bullion weighing three and a half Roman

_librae_. The _aqua_ which parts the one from the other is poured into

it, and the ampulla is placed in sand contained in an earthen vessel, or

in a box, that it may be warmed with a gentle fire. Lest the _aqua_

should be exhaled, the top of the ampulla is plastered on all sides with

lute, and it is covered with a glass operculum, under whose spout is

placed another ampulla which receives the distilled drops; this receiver

is likewise arranged in a box containing sand. When the contents are

heated it reddens, but when the redness no longer appears to increase,

it is taken out of the vessel or box and shaken; by this motion the

_aqua_ becomes heated again and grows red; if this is done two or three

times before other _aqua_ is added to it, the operation is sooner

concluded, and much less _aqua_ is consumed. When the first charge has

all been distilled, as much silver as at first is again put into the

ampulla, for if too much were put in at once, the gold would be parted

from it with difficulty. Then the second _aqua_ is poured in, but it is

warmed in order that it and the ampulla may be of equal temperature, so

that the latter may not be cracked by the cold; also if a cold wind

blows on it, it is apt to crack. Then the third _aqua_ is poured in, and

also if circumstances require it, the fourth, that is to say more _aqua_

and again more is poured in until the gold assumes the colour of burned

brick. The artificer keeps in hand two _aquae_, one of which is stronger

than the other; the stronger is used at first, then the less strong,

then at the last again the stronger. When the gold becomes of a reddish

yellow colour, spring water is poured in and heated until it boils. The

gold is washed four times and then heated in the crucible until it

melts. The water with which it was washed is put back, for there is a

little silver in it; for this reason it is poured into an ampulla and

heated, and the drops first distilled are received by one ampulla, while

those which come later, that is to say when the operculum begins to get

red, fall into another. This latter _aqua_ is useful for testing the

gold, the former for washing it; the former may also be poured over the

ingredients from which the _aqua valens_ is made.

The _aqua_ that was first distilled, which contains the silver, is

poured into an ampulla wide at the base, the top of which is also

smeared with lute and covered by an operculum, and is then boiled as

before in order that it may be separated from the silver. If there be so

much _aqua_ that (when boiled) it rises into the operculum, there is

put into the ampulla one lozenge or two; these are made of soap, cut

into small pieces and mixed together with powdered argol, and then

heated in a pot over a gentle fire; or else the contents are stirred

with a hazel twig split at the bottom, and in both cases the _aqua_

effervesces, and soon after again settles. When the powerful vapour

appears, the _aqua_ gives off a kind of oil, and the operculum becomes

red. But, lest the vapours should escape from the ampulla and the

operculum in that part where their mouths communicate, they are entirely

sealed all round. The _aqua_ is boiled continually over a fiercer fire,

and enough charcoal must be put into the furnace so that the live coals

touch the vessel. The ampulla is taken out as soon as all the _aqua_ has

been distilled, and the silver, which is dried by the heat of the fire,

alone remains in it; the silver is shaken out and put in an earthenware

crucible, and heated until it melts. The molten glass is extracted with

an iron rod curved at the lower end, and the silver is made into cakes.

The glass extracted from the crucible is ground to powder, and to this

are added litharge, argol, glass-galls, and saltpetre, and they are

melted in an earthen crucible. The button that settles is transferred to

the cupel and re-melted.

If the silver was not sufficiently dried by the heat of the fire, that

which is contained in the upper part of the ampulla will appear black;

this when melted will be consumed. When the lute, which was smeared

round the lower part of the ampulla, has been removed, it is placed in

the crucible and is re-melted, until at last there is no more appearance

of black[13].

If to the first _aqua_ the other which contains silver is to be added,

it must be poured in before the powerful vapours appear, and the _aqua_

gives off the oily substance, and the operculum becomes red; for he who

pours in the _aqua_ after the vapour appears causes a loss, because the

_aqua_ generally spurts out and the glass breaks. If the ampulla breaks

when the gold is being parted from the silver or the silver from the

_aqua_, the _aqua_ will be absorbed by the sand or the lute or the

bricks, whereupon, without any delay, the red hot coals should be taken

out of the furnace and the fire extinguished. The sand and bricks after

being crushed should be thrown into a copper vessel, warm water should

be poured over them, and they should be put aside for the space of

twelve hours; afterward the water should be strained through a canvas,

and the canvas, since it contains silver, should be dried by the heat of

the sun or the fire, and then placed in an earthen crucible and heated

until the silver melts, this being poured out into an iron mould. The

strained water should be poured into an ampulla and separated from the

silver, of which it contains a minute portion; the sand should be mixed

with litharge, glass-galls, argol, saltpetre, and salt, and heated in an

earthen crucible. The button which settles at the bottom should be

transferred to a cupel, and should be re-melted, in order that the lead

may be separated from the silver. The lute, with lead added, should be

heated in an earthen crucible, then re-melted in a cupel.

We also separate silver from gold by the same method when we assay them.

For this purpose the alloy is first rubbed against a touchstone, in

order to learn what proportion of silver there is in it; then as much

silver as is necessary is added to the argentiferous gold, in a _bes_ of

which there must be less than a _semi-uncia_ or a _semi-uncia_ and a

_sicilicus_[14] of copper. After lead has been added, it is melted in a

cupel until the lead and the copper have exhaled, then the alloy of gold

with silver is flattened out, and little tubes are made of the leaves;

these are put into a glass ampulla, and strong _aqua_ is poured over

them two or three times. The tubes after this are absolutely pure, with

the exception of only a quarter of a _siliqua_, which is silver; for

only this much silver remains in eight _unciae_ of gold[15].

As great expense is incurred in parting the metals by the methods that

I have explained, as night vigils are necessary when _aqua valens_ is

made, and as generally much labour and great pains have to be expended

on this matter, other methods for parting have been invented by clever

men, which are less costly, less laborious, and in which there is less

loss if through carelessness an error is made. There are three methods,

the first performed with sulphur, the second with antimony, the third by

means of some compound which consists of these or other ingredients.

[Illustration 449 (Parting precious metals with sulphur): A--Pot.

B--Circular fire. C--Crucibles. D--Their lids. E--Lid of the pot.

F--Furnace. G--Iron rod.]

In the first method,[16] the silver containing some gold is melted in a

crucible and made into granules. For every _libra_ of granules, there is

taken a sixth of a _libra_ and a _sicilicus_ of sulphur (not exposed to

the fire); this, when crushed, is sprinkled over the moistened granules,

and then they are put into a new earthen pot of the capacity of four

_sextarii_, or into several of them if there is an abundance of

granules. The pot, having been filled, is covered with an earthen lid

and smeared over, and placed within a circle of fire set one and a half

feet distant from the pot on all sides, in order that the sulphur added

to the silver should not be distilled when melted. The pot is opened,

the black-coloured granules are taken out, and afterward thirty-three

_librae_ of these granules are placed in an earthen crucible, if it has

such capacity. For every _libra_ of silver granules, weighed before they

were sprinkled with sulphur, there is weighed out also a sixth of a

_libra_ and a _sicilicus_ of copper, if each _libra_ consists either of

three-quarters of a _libra_ of silver and a quarter of a _libra_ of

copper, or of three-quarters of a _libra_ and a _semi-uncia_ of silver

and a sixth of a _libra_ and a _semi-uncia_ of copper. If, however, the

silver contains five-sixths of a _libra_ of silver and a sixth of a

_libra_ of copper, or five-sixths of a _libra_ and a _semi-uncia_ of

silver and an _uncia_ and a half of copper, then there are weighed out a

quarter of a _libra_ of copper granules. If a _libra_ contains

eleven-twelfths of a _libra_ of silver and one _uncia_ of copper, or

eleven-twelfths and a _semi-uncia_ of silver and a _semi-uncia_ of

copper, then are weighed out a quarter of a _libra_ and a _semi-uncia_

and a _sicilicus_ of copper granules. Lastly, if there is only pure

silver, then as much as a third of a _libra_ and a _semi-uncia_ of

copper granules are added. Half of these copper granules are added soon

afterward to the black-coloured silver granules. The crucible should be

tightly covered and smeared over with lute, and placed in a furnace,

into which the air is drawn through the draught-holes. As soon as the

silver is melted, the crucible is opened, and there is placed in it a

heaped ladleful more of granulated copper, and also a heaped ladleful of

a powder which consists of equal parts of litharge, of granulated lead,

of salt, and of glass-galls; then the crucible is again covered with the

lid. When the copper granules are melted, more are put in, together with

the powder, until all have been put in.

A little of the regulus is taken from the crucible, but not from the

gold lump which has settled at the bottom, and a _drachma_ of it is put

into each of the cupels, which contain an _uncia_ of molten lead; there

should be many of these cupels. In this way half a _drachma_ of silver

is made. As soon as the lead and copper have been separated from the

silver, a third of it is thrown into a glass ampulla, and _aqua valens_

is poured over it. By this method is shown whether the sulphur has

parted all the gold from the silver, or not. If one wishes to know the

size of the gold lump which has settled at the bottom of the crucible,

an iron rod moistened with water is covered with chalk, and when the rod

is dry it is pushed down straight into the crucible, and the rod remains

bright to the height of the gold lump; the remaining part of the rod is

coloured black by the regulus, which adheres to the rod if it is not

quickly removed.

If when the rod has been extracted the gold is observed to be

satisfactorily parted from the silver, the regulus is poured out, the

gold button is taken out of the crucible, and in some clean place the

regulus is chipped off from it, although it usually flies apart. The

lump itself is reduced to granules, and for every _libra_ of this gold

they weigh out a quarter of a _libra_ each of crushed sulphur and of

granular copper, and all are placed together in an earthen crucible, not

into a pot. When they are melted, in order that the gold may more

quickly settle at the bottom, the powder which I have mentioned is

added.

Although minute particles of gold appear to scintillate in the regulus

of copper and silver, yet if all that are in a _libra_ do not weigh as

much as a single sesterce, then the sulphur has satisfactorily parted

the gold from the silver; but if it should weigh a sesterce or more,

then the regulus is thrown back again into the earthen crucible, and it

is not advantageous to add sulphur, but only a little copper and powder,

by which method a gold lump is again made to settle at the bottom; and

this one is added to the other button which is not rich in gold.

When gold is parted from sixty-six _librae_ of silver, the silver,

copper, and sulphur regulus weighs one hundred and thirty-two _librae_.

To separate the copper from the silver we require five hundred _librae_

of lead, more or less, with which the regulus is melted in the second

furnace. In this manner litharge and hearth-lead are made, which are

re-smelted in the first furnace. The cakes that are made from these are

placed in the third furnace, so that the lead may be separated from the

copper and used again, for it contains very little silver. The crucibles

and their covers are crushed, washed, and the sediment is melted

together with litharge and hearth-lead.

Those who wish to separate all the silver from the gold by this method

leave one part of gold to three of silver, and then reduce the alloy to

granules. Then they place it in an ampulla, and by pouring _aqua valens_

over it, part the gold from the silver, which process I explained in

Book VII.

If sulphur from the lye with which _sal artificiosus_ is made, is strong

enough to float an egg thrown into it, and is boiled until it no longer

emits fumes, and melts when placed upon glowing coals, then, if such

sulphur is thrown into the melted silver, it parts the gold from it.

[Illustration 453 (Parting precious metals with antimony): A--Furnace in

which the air is drawn in through holes. B--Goldsmith's forge.

C--Earthen crucibles. D--Iron pots. E--Block.]

Silver is also parted from gold by means of _stibium_[17]. If in a _bes

of_ gold there are seven, or six, or five double _sextulae_ of silver,

then three parts of _stibium_ are added to one part of gold; but in

order that the _stibium_ should not consume the gold, it is melted with

copper in a red hot earthen crucible. If the gold contains some portion

of copper, then to eight _unciae_ of _stibium_ a _sicilicus_ of copper

is added; and if it contains no copper, then half an _uncia_, because

copper must be added to _stibium_ in order to part gold from silver. The

gold is first placed in a red hot earthen crucible, and when melted it

swells, and a little _stibium_ is added to it lest it run over; in a

short space of time, when this has melted, it likewise again swells, and

when this occurs it is advisable to put in all the remainder of the

_stibium_, and to cover the crucible with a lid, and then to heat the

mixture for the time required to walk thirty-five paces. Then it is at

once poured out into an iron pot, wide at the top and narrow at the

bottom, which was first heated and smeared over with tallow or wax, and

set on an iron or wooden block. It is shaken violently, and by this

agitation the gold lump settles to the bottom, and when the pot has

cooled it is tapped loose, and is again melted four times in the same

way. But each time a less weight of _stibium_ is added to the gold,

until finally only twice as much _stibium_ is added as there is gold, or

a little more; then the gold lump is melted in a cupel. The _stibium_ is

melted again three or four times in an earthen crucible, and each time a

gold lump settles, so that there are three or four gold lumps, and these

are all melted together in a cupel.

To two _librae_ and a half of such _stibium_ are added two _librae_ of

argol and one _libra_ of glass-galls, and they are melted in an earthen

crucible, where a lump likewise settles at the bottom; this lump is

melted in the cupel. Finally, the _stibium_ with a little lead added, is

melted in the cupel, in which, after all the rest has been consumed by

the fire, the silver alone remains. If the _stibium_ is not first melted

in an earthen crucible with argol and glass-galls, before it is melted

in the cupel, part of the silver is consumed, and is absorbed by the ash

and powder of which the cupel is made.

The crucible in which the gold and silver alloy are melted with

_stibium_, and also the cupel, are placed in a furnace, which is usually

of the kind in which the air is drawn in through holes; or else they

are placed in a goldsmith's forge.

Just as _aqua valens_ poured over silver, from which the sulphur has

parted the gold, shows us whether all has been separated or whether

particles of gold remain in the silver; so do certain ingredients, if

placed in the pot or crucible "alternately" with the gold, from which

the silver has been parted by _stibium_, and heated, show us whether all

have been separated or not.

We use cements[18] when, without _stibium_, we part silver or copper or

both so ingeniously and admirably from gold. There are various cements.

Some consist of half a _libra_ of brick dust, a quarter of a _libra_ of

salt, an _uncia_ of saltpetre, half an _uncia_ of sal-ammoniac, and half

an _uncia_ of rock salt. The bricks or tiles from which the dust is made

must be composed of fatty clays, free from sand, grit, and small stones,

and must be moderately burnt and very old.

Another cement is made of a _bes_ of brick dust, a third of rock salt,

an _uncia_ of saltpetre, and half an _uncia_ of refined salt. Another

cement is made of a _bes_ of brick dust, a quarter of refined salt, one

and a half _unciae_ of saltpetre, an _uncia_ of sal-ammoniac, and half

an _uncia_ of rock salt. Another has one _libra_ of brick dust, and half

a _libra_ of rock salt, to which some add a sixth of a _libra_ and a

_sicilicus_ of vitriol. Another is made of half a _libra_ of brick dust,

a third of a _libra_ of rock salt, an _uncia_ and a half of vitriol, and

one _uncia_ of saltpetre. Another consists of a _bes_ of brick dust, a

third of refined salt, a sixth of white vitriol[19], half an _uncia_ of

verdigris, and likewise half an _uncia_ of saltpetre. Another is made of

one and a third _librae_ of brick dust, a _bes_ of rock salt, a sixth of

a _libra_ and half an _uncia_ of sal-ammoniac, a sixth and half an

_uncia_ of vitriol, and a sixth of saltpetre. Another contains a _libra_

of brick dust, a third of refined salt, and one and a half _unciae_ of

vitriol.

Those ingredients above are peculiar to each cement, but what follows

is common to all. Each of the ingredients is first separately crushed to

powder; the bricks are placed on a hard rock or marble, and crushed with

an iron implement; the other things are crushed in a mortar with a

pestle; each is separately passed through a sieve. Then they are all

mixed together, and are moistened with vinegar in which a little

sal-ammoniac has been dissolved, if the cement does not contain any. But

some workers, however, prefer to moisten the gold granules or gold-leaf

instead.

The cement should be placed, alternately with the gold, in new and clean

pots in which no water has ever been poured. In the bottom the cement is

levelled with an iron implement, and afterward the gold granules or

leaves are placed one against the other, so that they may touch it on

all sides; then, again, a handful of the cement, or more if the pots are

large, is thrown in and levelled with an iron implement; the granules

and leaves are laid over this in the same manner, and this is repeated

until the pot is filled. Then it is covered with a lid, and the place

where they join is smeared over with artificial lute, and when this is

dry the pots are placed in the furnace.

[Illustration 455 (Parting precious metals by cementation): A--Furnace.

B--Pot. C--Lid. D--Air-holes.]

The furnace has three chambers, the lowest of which is a foot high; into

this lowest chamber the air penetrates through an opening, and into it

the ashes fall from the burnt wood, which is supported by iron rods,

arranged to form a grating. The middle chamber is two feet high, and the

wood is pushed in through its mouth. The wood ought to be oak, holmoak,

or turkey-oak, for from these the slow and lasting fire is made which is

necessary for this operation. The upper chamber is open at the top so

that the pots, for which it has the depth, may be put into it; the floor

of this chamber consists of iron rods, so strong that they may bear the

weight of the pots and the heat of the fire; they are sufficiently far

apart that the fire may penetrate well and may heat the pots. The pots

are narrow at the bottom, so that the fire entering into the space

between them may heat them; at the top the pots are wide, so that they

may touch and hold back the heat of the fire. The upper part of the

furnace is closed in with bricks not very thick, or with tiles and lute,

and two or three air-holes are left, through which the fumes and flames

may escape.

The gold granules or leaves and the cement, alternately placed in the

pots, are heated by a gentle fire, gradually increasing for twenty-four

hours, if the furnace was heated for two hours before the full pots were

stood in it, and if this was not done, then for twenty-six hours. The

fire should be increased in such a manner that the pieces of gold and

the cement, in which is the potency to separate the silver and copper

from the gold, may not melt, for in this case the labour and cost will

be spent in vain; therefore, it is ample to have the fire hot enough

that the pots always remain red. After so many hours all the burning

wood should be drawn out of the furnace. Then the refractory bricks or

tiles are removed from the top of the furnace, and the glowing pots are

taken out with the tongs. The lids are removed, and if there is time it

is well to allow the gold to cool by itself, for then there is less

loss; but if time cannot be spared for that operation, the pieces of

gold are immediately placed separately into a wooden or bronze vessel of

water and gradually quenched, lest the cement which absorbs the silver

should exhale it. The pieces of gold, and the cement adhering to them,

when cooled or quenched, are rolled with a little mallet so as to crush

the lumps and free the gold from the cement. Then they are sifted by a

fine sieve, which is placed over a bronze vessel; in this manner the

cement containing the silver or the copper or both, falls from the sieve

into the bronze vessel, and the gold granules or leaves remain on it.

The gold is placed in a vessel and again rolled with the little mallet,

so that it may be cleansed from the cement which absorbs silver and

copper.

The particles of cement, which have dropped through the holes of the

sieve into the bronze vessel, are washed in a bowl, over a wooden tub,

being shaken about with the hands, so that the minute particles of gold

which have fallen through the sieve may be separated. These are again

washed in a little vessel, with warm water, and scrubbed with a piece of

wood or a twig broom, that the moistened cement may be detached.

Afterward all the gold is again washed with warm water, and collected

with a bristle brush, and should be washed in a copper full of holes,

under which is placed a little vessel. Then it is necessary to put the

gold on an iron plate, under which is a vessel, and to wash it with

warm water. Finally, it is placed in a bowl, and, when dry, the granules

or leaves are rubbed against a touchstone at the same time as a

touch-needle, and considered carefully as to whether they be pure or

alloyed. If they are not pure enough, the granules or the leaves,

together with the cement which attracts silver and copper, are arranged

alternately in layers in the same manner, and again heated; this is done

as often as is necessary, but the last time it is heated as many hours

as are required to cleanse the gold.

Some people add another cement to the granules or leaves. This cement

lacks the ingredients of metalliferous origin, such as verdigris and

vitriol, for if these are in the cement, the gold usually takes up a

little of the base metal; or if it does not do this, it is stained by

them. For this reason some very rightly never make use of cements

containing these things, because brick dust and salt alone, especially

rock salt, are able to extract all the silver and copper from the gold

and to attract it to themselves.

It is not necessary for coiners to make absolutely pure gold, but to

heat it only until such a fineness is obtained as is needed for the gold

money which they are coining.

The gold is heated, and when it shows the necessary golden yellow colour

and is wholly pure, it is melted and made into bars, in which case they

are either prepared by the coiners with _chrysocolla_, which is called

by the Moors borax, or are prepared with salt of lye made from the ashes

of ivy or of other salty herbs.

The cement which has absorbed silver or copper, after water has been

poured over it, is dried and crushed, and when mixed with hearth-lead

and de-silverized lead, is smelted in the blast furnace. The alloy of

silver and lead, or of silver and copper and lead, which flows out, is

again melted in the cupellation furnace, in order that the lead and

copper may be separated from the silver. The silver is finally

thoroughly purified in the refining furnace, and in this practical

manner there is no silver lost, or only a minute quantity.

There are besides this, certain other cements[20] which part gold from

silver, composed of sulphur, _stibium_ and other ingredients. One of

these compounds consists of half an _uncia_ of vitriol dried by the heat

of the fire and reduced to powder, a sixth of refined salt, a third of

_stibium_, half a _libra_ of prepared sulphur (not exposed to the

fire), one _sicilicus_ of glass, likewise one _sicilicus_ of saltpetre,

and a _drachma_ of sal-ammoniac.[21] The sulphur is prepared as follows:

it is first crushed to powder, then it is heated for six hours in sharp

vinegar, and finally poured into a vessel and washed with warm water;

then that which settles at the bottom of the vessel is dried. To refine

the salt it is placed in river water and boiled, and again evaporated.

The second compound contains one _libra_ of sulphur (not exposed to

fire) and two _librae_ of refined salt. The third compound is made from

one _libra_ of sulphur (not exposed to the fire), half a _libra_ of

refined salt, a quarter of a _libra_ of sal-ammoniac, and one _uncia_ of

red-lead. The fourth compound consists of one _libra_ each of refined

salt, sulphur (not exposed to the fire) and argol, and half a _libra_ of

_chrysocolla_ which the Moors call borax. The fifth compound has equal

proportions of sulphur (not exposed to the fire), sal-ammoniac,

saltpetre, and verdigris.

The silver which contains some portion of gold is first melted with lead

in an earthen crucible, and they are heated together until the silver

exhales the lead. If there was a _libra_ of silver, there must be six

_drachmae_ of lead. Then the silver is sprinkled with two _unciae_ of

that powdered compound and is stirred; afterward it is poured into

another crucible, first warmed and lined with tallow, and then violently

shaken. The rest is performed according to the process I have already

explained.

Gold may be parted without injury from silver goblets and from other

gilt vessels and articles[22], by means of a powder, which consists of

one part of sal-ammoniac and half a part of sulphur. The gilt goblet or

other article is smeared with oil, and the powder is dusted on; the

article is seized in the hand, or with tongs, and is carried to the fire

and sharply tapped, and by this means the gold falls into water in

vessels placed underneath, while the goblet remains uninjured.

Gold is also parted from silver on gilt articles by means of

quicksilver. This is poured into an earthen crucible, and so warmed by

the fire that the finger can bear the heat when dipped into it; the

silver-gilt objects are placed in it, and when the quicksilver adheres

to them they are taken out and placed on a dish, into which, when

cooled, the gold falls, together with the quicksilver. Again and

frequently the same silver-gilt object is placed in heated quicksilver,

and the same process is continued until at last no more gold is visible

on the object; then the object is placed in the fire, and the

quicksilver which adheres to it is exhaled. Then the artificer takes a

hare's foot, and brushes up into a dish the quicksilver and the gold

which have fallen together from the silver article, and puts them into

a cloth made of woven cotton or into a soft leather; the quicksilver is

squeezed through one or the other into another dish.[23] The gold

remains in the cloth or the leather, and when collected is placed in a

piece of charcoal hollowed out, and is heated until it melts, and a

little button is made from it. This button is heated with a little

_stibium_ in an earthen crucible and poured out into another little

vessel, by which method the gold settles at the bottom, and the

_stibium_ is seen to be on the top; then the work is completed. Finally,

the gold button is put in a hollowed-out brick and placed in the fire,

and by this method the gold is made pure. By means of the above methods

gold is parted from silver and also silver from gold.

Now I will explain the methods used to separate copper from gold[24].

The salt which we call _sal-artificiosus_,[25] is made from a _libra_

each of vitriol, alum, saltpetre, and sulphur not exposed to the fire,

and half a _libra_ of sal-ammoniac; these ingredients when crushed are

heated with one part of lye made from the ashes used by wool dyers, one

part of unslaked lime, and four parts of beech ashes. The ingredients

are boiled in the lye until the whole has been dissolved. Then it is

immediately dried and kept in a hot place, lest it turn into oil; and

afterward when crushed, a _libra_ of lead-ash is mixed with it. With

each _libra_ of this powdered compound one and a half _unciae_ of the

copper is gradually sprinkled into a hot crucible, and it is stirred

rapidly and frequently with an iron rod. When the crucible has cooled

and been broken up, the button of gold is found.

The second method for parting is the following. Two _librae_ of sulphur

not exposed to the fire, and four _librae_ of refined salt are crushed

and mixed; a sixth of a _libra_ and half an _uncia_ of this powder is

added to a _bes_ of granules made of lead, and twice as much copper

containing gold; they are heated together in an earthen crucible until

they melt. When cooled, the button is taken out and purged of slag. From

this button they again make granules, to a third of a _libra_ of which

is added half a _libra_ of that powder of which I have spoken, and they

are placed in alternate layers in the crucible; it is well to cover the

crucible and to seal it up, and afterward it is heated over a gentle

fire until the granules melt. Soon afterward, the crucible is taken off

the fire, and when it is cool the button is extracted. From this, when

purified and again melted down, the third granules are made, to which,

if they weigh a sixth of a _libra_, is added one half an _uncia_ and a

_sicilicus_ of the powder, and they are heated in the same manner, and

the button of gold settles at the bottom of the crucible.

The third method is as follows. From time to time small pieces of

sulphur, enveloped in or mixed with wax, are dropped into six _librae_

of the molten copper, and consumed; the sulphur weighs half an _uncia_

and a _sicilicus_. Then one and a half _sicilici_ of powdered saltpetre

are dropped into the same copper and likewise consumed; then again half

an _uncia_ and a _sicilicus_ of sulphur enveloped in wax; afterward one

and a half _sicilici_ of lead-ash enveloped in wax, or of minium made

from red-lead. Then immediately the copper is taken out, and to the gold

button, which is now mixed with only a little copper, they add _stibium_

to double the amount of the button; these are heated together until the

_stibium_ is driven off; then the button, together with lead of half the

weight of the button, are heated in a cupel. Finally, the gold is taken

out of this and quenched, and if there is a blackish colour settled in

it, it is melted with a little of the _chrysocolla_ which the Moors call

borax; if too pale, it is melted with _stibium_, and acquires its own

golden-yellow colour. There are some who take out the molten copper with

an iron ladle and pour it into another crucible, whose aperture is

sealed up with lute, and they place it over glowing charcoal, and when

they have thrown in the powders of which I have spoken, they stir the

whole mass rapidly with an iron rod, and thus separate the gold from the

copper; the former settles at the bottom of the crucible, the latter

floats on the top. Then the aperture of the crucible is opened with the

red-hot tongs, and the copper runs out. The gold which remains is

re-heated with _stibium_, and when this is exhaled the gold is heated

for the third time in a cupel with a fourth part of lead, and then

quenched.

The fourth method is to melt one and a third _librae_ of the copper with

a sixth of a _libra_ of lead, and to pour it into another crucible

smeared on the inside with tallow or gypsum; and to this is added a

powder consisting of half an _uncia_ each of prepared sulphur,

verdigris, and saltpetre, and an _uncia_ and a half of _sal coctus_. The

fifth method consists of placing in a crucible one _libra_ of the copper

and two _librae_ of granulated lead, with one and a half _unciae_ of

_sal-artificiosus_; they are at first heated over a gentle fire and then

over a fiercer one. The sixth method consists in heating together a

_bes_ of the copper and one-sixth of a _libra_ each of sulphur, salt,

and _stibium_. The seventh method consists of heating together a _bes_

of the copper and one-sixth each of iron scales and filings, salt,

_stibium_, and glass-galls. The eighth method consists of heating

together one _libra_ of the copper, one and a half _librae_ of sulphur,

half a _libra_ of verdigris, and a _libra_ of refined salt. The ninth

method consists of placing in one _libra_ of the molten copper as much

pounded sulphur, not exposed to the fire, and of stirring it rapidly

with an iron rod; the lump is ground to powder, into which quicksilver

is poured, and this attracts to itself the gold.

Gilded copper articles are moistened with water and placed on the fire,

and when they are glowing they are quenched with cold water, and the

gold is scraped off with a brass rod. By these practical methods gold is

separated from copper.

Either copper or lead is separated from silver by the methods which I

will now explain.[26] This is carried on in a building near by the

works, or in the works in which the gold or silver ores or alloys are

smelted. The middle wall of such a building is twenty-one feet long and

fifteen feet high, and from this a front wall is distant fifteen feet

toward the river; the rear wall is nineteen feet distant, and both

these walls are thirty-six feet long and fourteen feet high; a

transverse wall extends from the end of the front wall to the end of the

rear wall; then fifteen feet back a second transverse wall is built out

from the front wall to the end of the middle wall. In that space which

is between those two transverse walls are set up the stamps, by means of

which the ores and the necessary ingredients for smelting are broken up.

From the further end of the front wall, a third transverse wall leads to

the other end of the middle wall, and from the same to the end of the

rear wall. The space between the second and third transverse walls, and

between the rear and middle long walls, contains the cupellation

furnace, in which lead is separated from gold or silver. The vertical

wall of its chimney is erected upon the middle wall, and the sloping

chimney-wall rests on the beams which extend from the second transverse

wall to the third; these are so located that they are at a distance of

thirteen feet from the middle long wall and four from the rear wall, and

they are two feet wide and thick. From the ground up to the roof-beams

is twelve feet, and lest the sloping chimney-wall should fall down, it

is partly supported by means of many iron rods, and partly by means of a

few tie-beams covered with lute, which extend from the small beams of

the sloping chimney-wall to the beams of the vertical chimney-wall. The

rear roof is arranged in the same way as the roof of the works in which

ore is smelted. In the space between the middle and the front long walls

and between the second[27] and the third transverse walls are the

bellows, the machinery for depressing and the instrument for raising

them. A drum on the axle of a water-wheel has rundles which turn the

toothed drum of an axle, whose long cams depress the levers of the

bellows, and also another toothed drum on an axle, whose cams raise the

tappets of the stamps, but in the opposite direction. So that if the

cams which depress the levers of the bellows turn from north to south,

the cams of the stamps turn from south to north.

[Illustration 468 (Cupellation Furnace): A--Rectangular stones.

B--Sole-stone. C--Air-holes. D--Internal walls. E--Dome. F--Crucible.

G--Bands. H--Bars. I--Apertures in the dome. K--Lid of the dome.

L--Rings. M--Pipes. N--Valves. O--Chains.]

Lead is separated from gold or silver in a cupellation furnace, of which

the structure consists of rectangular stones, of two interior walls of

which the one intersects the other transversely, of a round sole, and of

a dome. Its crucible is made from powder of earth and ash; but I will

first speak of the structure and also of the rectangular stones. A

circular wall is built four feet and three palms high, and one foot

thick; from the height of two feet and three palms from the bottom, the

upper part of the interior is cut away to the width of one palm, so that

the stone sole may rest upon it. There are usually as many as fourteen

stones; on the outside they are a foot and a palm wide, and on the

inside narrower, because the inner circle is much smaller than the

outer; if the stones are wider, fewer are required, if narrower more;

they are sunk into the earth to a depth of a foot and a palm. At the top

each one is joined to the next by an iron staple, the points of which

are embedded in holes, and into each hole is poured molten lead. This

stone structure has six air-holes near the ground, at a height of a foot

above the ground; they are two feet and a palm from the bottom of the

stones; each of these air-holes is in two stones, and is two palms high,

and a palm and three digits wide. One of them is on the right side,

between the wall which protects the main wall from the fire, and the

channel through which the litharge flows out of the furnace crucible;

the other five air-holes are distributed all round at equal distances

apart; through these escapes the moisture which the earth exhales when

heated, and if it were not for these openings the crucible would absorb

the moisture and be damaged. In such a case a lump would be raised, like

that which a mole throws up from the earth, and the ash would float on

the top, and the crucible would absorb the silver-lead alloy; there are

some who, because of this, make the rear part of the structure entirely

open. The two inner walls, of which one intersects the other, are built

of bricks, and are a brick in thickness. There are four air-holes in

these, one in each part, which are about one digit's breadth higher and

wider than the others. Into the four compartments is thrown a

wheelbarrowful of slag, and over this is placed a large wicker basket

full of charcoal dust. These walls extend a cubit above the ground, and

on these, and on the ledge cut in the rectangular stones, is placed the

stone sole; this sole is a palm and three digits thick, and on all sides

touches the rectangular stones; if there are any cracks in it they are

filled up with fragments of stone or brick. The front part of the sole

is sloped so that a channel can be made, through which the litharge

flows out. Copper plates are placed on this part of the sole-stone so

that the silver-lead or other alloy may be more rapidly heated.

A dome which has the shape of half a sphere covers the crucible. It

consists of iron bands and of bars and of a lid. There are three bands,

each about a palm wide and a digit thick; the lowest is at a distance of

one foot from the middle one, and the middle one a distance of two feet

from the upper one. Under them are eighteen iron bars fixed by iron

rivets; these bars are of the same width and thickness as the bands, and

they are of such a length, that curving, they reach from the lower band

to the upper, that is two feet and three palms long, while the dome is

only one foot and three palms high. All the bars and bands of the dome

have iron plates fastened on the underside with iron wire. In addition,

the dome has four apertures; the rear one, which is situated opposite

the channel through which the litharge flows out, is two feet wide at

the bottom; toward the top, since it slopes gently, it is narrower,

being a foot, three palms, and a digit wide; there is no bar at this

place, for the aperture extends from the upper band to the middle one,

but not to the lower one. The second aperture is situated above the

channel, is two and a half feet wide at the bottom, and two feet and a

palm at the top; and there is likewise no bar at this point; indeed, not

only does the bar not extend to the lower band, but the lower band

itself does not extend over this part, in order that the master can draw

the litharge out of the crucible. There are besides, in the wall which

protects the principal wall against the heat, near where the nozzles of

the bellows are situated, two apertures, three palms wide and about a

foot high, in the middle of which two rods descend, fastened on the

inside with plates. Near these apertures are placed the nozzles of the

bellows, and through the apertures extend the pipes in which the nozzles

of the bellows are set. These pipes are made of iron plates rolled up;

they are two palms three digits long, and their inside diameter is three

and a half digits; into these two pipes the nozzles of the bellows

penetrate a distance of three digits from their valves. The lid of the

dome consists of an iron band at the bottom, two digits wide, and of

three curved iron bars, which extend from one point on the band to the

point opposite; they cross each other at the top, where they are fixed

by means of iron rivets. On the under side of the bars there are

likewise plates fastened by rivets; each of the plates has small holes

the size of a finger, so that the lute will adhere when the interior is

lined. The dome has three iron rings engaged in wide holes in the heads

of iron claves, which fasten the bars to the middle band at these

points. Into these rings are fastened the hooks of the chains with which

the dome is raised, when the master is preparing the crucible.

On the sole and the copper plates and the rock of the furnace, lute

mixed with straw is placed to a depth of three digits, and it is pounded

with a wooden rammer until it is compressed to a depth of one digit

only. The rammer-head is round and three palms high, two palms wide at

the bottom, and tapering upward; its handle is three feet long, and

where it is set into the rammer-head it is bound around with an iron

band. The top of the stonework in which the dome rests is also covered

with lute, likewise mixed with straw, to the thickness of a palm. All

this, as soon as it becomes loosened, must be repaired.

[Illustration 470 (Cupellation Furnace): A--An artificer tamping the

crucible with a rammer. B--Large rammer. C--Broom. D--Two smaller

rammers. E--Curved iron plates. F--Part of a wooden strip. G--Sieve.

H--Ashes. I--Iron shovel. K--Iron plate. L--block of wood. M--Rock.

N--Basket made of woven twigs. O--Hooked bar. P--Second hooked bar.

Q--Old linen rag. R--bucket. S--Doeskin. T--Bundles of straw. V--Wood.

X--Cakes of lead alloy. Y--Fork. Z--Another workman covers the outside

of the furnace with lute where the dome fits on it. AA--Basket full of

ashes. BB--Lid of the dome. CC--The assistant standing on the steps

pours charcoal into the crucible through the hole at the top of the

dome. DD--Iron implement with which the lute is beaten. EE--Lute.

FF--Ladle with which the workman or master takes a sample. GG--Rabble

with which the scum of impure lead is drawn off. HH--Iron wedge with

which the silver mass is raised.]

The artificer who undertakes the work of parting the metals, distributes

the operation into two shifts of two days. On the one morning he

sprinkles a little ash into the lute, and when he has poured some water

over it he brushes it over with a broom. Then he throws in sifted ashes

and dampens them with water, so that they could be moulded into balls

like snow. The ashes are those from which lye has been made by letting

water percolate through them, for other ashes which are fatty would have

to be burnt again in order to make them less fat. When he has made the

ashes smooth by pressing them with his hands, he makes the crucible

slope down toward the middle; then he tamps it, as I have described,

with a rammer. He afterward, with two small wooden rammers, one held in

each hand, forms the channel through which the litharge flows out. The

heads of these small rammers are each a palm wide, two digits thick, and

one foot high; the handle of each is somewhat rounded, is a digit and a

half less in diameter than the rammer-head, and is three feet in

length; the rammer-head as well as the handle is made of one piece of

wood. Then with shoes on, he descends into the crucible and stamps it in

every direction with his feet, in which manner it is packed and made

sloping. Then he again tamps it with a large rammer, and removing his

shoe from his right foot he draws a circle around the crucible with it,

and cuts out the circle thus drawn with an iron plate. This plate is

curved at both ends, is three palms long, as many digits wide, and has

wooden handles a palm and two digits long, and two digits thick; the

iron plate is curved back at the top and ends, which penetrate into

handles. There are some who use in the place of the plate a strip of

wood, like the rim of a sieve; this is three digits wide, and is cut out

at both ends that it may be held in the hands. Afterward he tamps the

channel through which the litharge discharges. Lest the ashes should

fall out, he blocks up the aperture with a stone shaped to fit it,

against which he places a board, and lest this fall, he props it with a

stick. Then he pours in a basketful of ashes and tamps them with the

large rammer; then again and again he pours in ashes and tamps them with

the rammer. When the channel has been made, he throws dry ashes all over

the crucible with a sieve, and smooths and rubs it with his hands. Then

he throws three basketsful of damp ashes on the margin all round the

edge of the crucible, and lets down the dome. Soon after, climbing upon

the crucible, he builds up ashes all around it, lest the molten alloy

should flow out. Then, having raised the lid of the dome, he throws a

basketful of charcoal into the crucible, together with an iron shovelful

of glowing coals, and he also throws some of the latter through the

apertures in the sides of the dome, and he spreads them with the same

shovel. This work and labour is finished in the space of two hours.

An iron plate is set in the ground under the channel, and upon this is

placed a wooden block, three feet and a palm long, a foot and two palms

and as many digits wide at the back, and two palms and as many digits

wide in front; on the block of wood is placed a stone, and over it an

iron plate similar to the bottom one, and upon this he puts a basketful

of charcoal, and also an iron shovelful of burning charcoals. The

crucible is heated in an hour, and then, with the hooked bar with which

the litharge is drawn off, he stirs the remainder of the charcoal about.

This hook is a palm long and three digits wide, has the form of a double

triangle, and has an iron handle four feet long, into which is set a

wooden one six feet long. There are some who use instead a simple hooked

bar. After about an hour's time, he stirs the charcoal again with the

bar, and with the shovel throws into the crucible the burning charcoals

lying in the channel; then again, after the space of an hour, he stirs

the burning charcoals with the same bar. If he did not thus stir them

about, some blackness would remain in the crucible and that part would

be damaged, because it would not be sufficiently dried. Therefore the

assistant stirs and turns the burning charcoal that it may be entirely

burnt up, and so that the crucible may be well heated, which takes three

hours; then the crucible is left quiet for the remaining two hours.

When the hour of eleven has struck, he sweeps up the charcoal ashes

with a broom and throws them out of the crucible. Then he climbs on to

the dome, and passing his hand in through its opening, and dipping an

old linen rag in a bucket of water mixed with ashes, he moistens the

whole of the crucible and sweeps it. In this way he uses two bucketsful

of the mixture, each holding five Roman _sextarii_,[28] and he does this

lest the crucible, when the metals are being parted, should break open;

after this he rubs the crucible with a doe skin, and fills in the

cracks. Then he places at the left side of the channel, two fragments of

hearth-lead, laid one on the top of the other, so that when partly

melted they remain fixed and form an obstacle, that the litharge will

not be blown about by the wind from the bellows, but remain in its

place. It is expedient, however, to use a brick in the place of the

hearth-lead, for as this gets much hotter, therefore it causes the

litharge to form more rapidly. The crucible in its middle part is made

two palms and as many digits deeper.[29]

There are some who having thus prepared the crucible, smear it over with

incense[30], ground to powder and dissolved in white of egg, soaking it

up in a sponge and then squeezing it out again; there are others who

smear over it a liquid consisting of white of egg and double the amount

of bullock's blood or marrow. Some throw lime into the crucible through

a sieve.

Afterward the master of the works weighs the lead with which the gold or

silver or both are mixed, and he sometimes puts a hundred

_centumpondia_[31] into the crucible, but frequently only sixty, or

fifty, or much less. After it has been weighed, he strews about in the

crucible three small bundles of straw, lest the lead by its weight

should break the surface. Then he places in the channel several cakes of

lead alloy, and through the aperture at the rear of the dome he places

some along the sides; then, ascending to the opening at the top of the

dome, he arranges in the crucible round about the dome the cakes which

his assistant hands to him, and after ascending again and passing his

hands through the same aperture, he likewise places other cakes inside

the crucible. On the second day those which remain he, with an iron

fork, places on the wood through the rear aperture of the dome.

When the cakes have been thus arranged through the hole at the top of

the dome, he throws in charcoal with a basket woven of wooden twigs.

Then he places the lid over the dome, and the assistant covers over the

joints with lute. The master himself throws half a basketful of charcoal

into the crucible through the aperture next to the nozzle pipe, and

prepares the bellows, in order to be able to begin the second operation

on the morning of the following day. It takes the space of one hour to

carry out such a piece of work, and at twelve all is prepared. These

hours all reckoned up make a sum of eight hours.

Now it is time that we should come to the second operation. In the

morning the workman takes up two shovelsful of live charcoals and throws

them into the crucible through the aperture next to the pipes of the

nozzles; then through the same hole he lays upon them small pieces of

fir-wood or of pitch pine, such as are generally used to cook fish.

After this the water-gates are opened, in order that the machine may be

turned which depresses the levers of the bellows. In the space of one

hour the lead alloy is melted; and when this has been done, he places

four sticks of wood, twelve feet long, through the hole in the back of

the dome, and as many through the channel; these sticks, lest they

should damage the crucible, are both weighted on the ends and supported

by trestles; these trestles are made of a beam, three feet long, two

palms and as many digits wide, two palms thick, and have two spreading

legs at each end. Against the trestle, in front of the channel, there is

placed an iron plate, lest the litharge, when it is extracted from the

furnace, should splash the smelter's shoes and injure his feet and legs.

With an iron shovel or a fork he places the remainder of the cakes

through the aperture at the back of the dome on to the sticks of wood

already mentioned.

The native silver, or silver glance, or grey silver, or ruby silver, or

any other sort, when it has been flattened out[32], and cut up, and

heated in an iron crucible, is poured into the molten lead mixed with

silver, in order that impurities may be separated. As I have often said,

this molten lead mixed with silver is called _stannum_[33].

[Illustration 474 (Cupellation Furnace): A--Furnace. B--Sticks of wood.

C--Litharge. D--Plate. E--The foreman when hungry eats butter, that the

poison which the crucible exhales may not harm him, for this is a

special remedy against that poison.]

When the long sticks of wood are burned up at the fore end, the master,

with a hammer, drives into them pointed iron bars, four feet long and

two digits wide at the front end, and beyond that one and a half digits

wide and thick; with these he pushes the sticks of wood forward and the

bars then rest on the trestles. There are others who, when they separate

metals, put two such sticks of wood into the crucible through the

aperture which is between the bellows, as many through the holes at the

back, and one through the channel; but in this case a larger number of

long sticks of wood is necessary, that is, sixty; in the former case,

forty long sticks of wood suffice to carry out the operation. When the

lead has been heated for two hours, it is stirred with a hooked bar,

that the heat may be increased.

If it be difficult to separate the lead from the silver, he throws

copper and charcoal dust into the molten silver-lead alloy. If the alloy

of argentiferous gold and lead, or the silver-lead alloy, contains

impurities from the ore, then he throws in either equal portions of

argol and Venetian glass or of sal-ammoniac, or of Venetian glass and of

Venetian soap; or else unequal portions, that is, two of argol and one

of iron rust; there are some who mix a little saltpetre with each

compound. To one _centumpondium_ of the alloy is added a _bes_ or a

_libra_ and a third of the powder, according to whether it is more or

less impure. The powder certainly separates the impurities from the

alloy. Then, with a kind of rabble he draws out through the channel,

mixed with charcoal, the scum, as one might say, of the lead; the lead

makes this scum when it becomes hot, but that less of it may be made it

must be stirred frequently with the bar.

Within the space of a quarter of an hour the crucible absorbs the lead;

at the time when it penetrates into the crucible it leaps and bubbles.

Then the master takes out a little lead with an iron ladle, which he

assays, in order to find what proportion of silver there is in the whole

of the alloy; the ladle is five digits wide, the iron part of its handle

is three feet long and the wooden part the same. Afterward, when they

are heated, he extracts with a bar the litharge which comes from the

lead and the copper, if there be any of it in the alloy. Wherefore, it

might more rightly be called _spuma_ of lead than of silver[34]. There

is no injury to the silver, when the lead and copper are separated from

it. In truth the lead becomes much purer in the crucible of the other

furnace, in which silver is refined. In ancient times, as the author

Pliny[35] relates, there was under the channel of the crucible another

crucible, and the litharge flowed down from the upper one into the lower

one, out of which it was lifted up and rolled round with a stick in

order that it might be of moderate weight. For which reason, they

formerly made it into small tubes or pipes, but now, since it is not

rolled round a stick, they make it into bars.

If there be any danger that the alloy might flow out with the litharge,

the foreman keeps on hand a piece of lute, shaped like a cylinder and

pointed at both ends; fastening this to a hooked bar he opposes it to

the alloy so that it will not flow out.

[Illustration 476 (Cleansing of Silver Cakes): A--Cake. B--Stone.

C--Hammer. D--Brass wire. E--Bucket containing water. F--Furnace from

which the cake has been taken, which is still smoking. G--Labourer

carrying a cake out of the works.]

Now when the colour begins to show in the silver, bright spots appear,

some of them being almost white, and a moment afterward it becomes

absolutely white. Then the assistant lets down the water-gates, so that,

the race being closed, the water-wheel ceases to turn and the bellows

are still. Then the master pours several buckets of water on to the

silver to cool it; others pour beer over it to make it whiter, but this

is of no importance since the silver has yet to be refined. Afterward,

the cake of silver is raised with the pointed iron bar, which is three

feet long and two digits wide, and has a wooden handle four feet long

fixed in its socket. When the cake of silver has been taken from the

crucible, it is laid upon a stone, and from part of it the hearth-lead,

and from the other part the litharge, is chipped away with a hammer;

then it is cleansed with a bundle of brass wire dipped in water. When

the lead is separated from the silver, more silver is frequently found

than when it was assayed; for instance, if before there were three

_unciae_ and as many _drachmae_ in a _centumpondium_, they now sometimes

find three _unciae_ and a half[36]. Often the hearth-lead remaining in

the crucible is a palm deep; it is taken out with the rest of the ashes

and is sifted, and that which remains in the sieve, since it is

hearth-lead, is added to the hearth-lead[37].

The ashes which pass through the sieve are of the same use as they were

at first, for, indeed, from these and pulverised bones they make the

cupels. Finally, when much of it has accumulated, the yellow _pompholyx_

adhering to the walls of the furnace, and likewise to those rings of the

dome near the apertures, is cleared away.

[Illustration 479 (Crane for cupellation furnace): A--Crane-post.

B--Socket. C--Oak cross-sills. D--Band. E--Roof-beam. F--Frame. G--Lower

small cross-beam. H--Upright timber. I--Bars which come from the sides

of the crane-post. K--Bars which come from the sides of the upright

timber. L--Rundle drums. M--Toothed wheels. N--Chain. O--Pulley.

P--Beams of the crane-arm. Q--Oblique beams supporting the beams of the

crane-arm. R--Rectangular iron plates. S--Trolley. T--Dome of the

furnace. V--Ring. X--Three chains. Y--Crank. Z--The crane-post of the

other contrivance. AA--Crane-arm. BB--Oblique beam. CC--Ring of the

crane-arm. DD--The second ring. EE--Lever-bar. FF--Third ring. GG--Hook.

HH--Chain of the dome. II--Chain of the lever-bar.]

I must also describe the crane with which the dome is raised. When it is

made, there is first set up a rectangular upright post twelve feet long,

each side of which measures a foot in width. Its lower pinion turns in a

bronze socket set in an oak sill; there are two sills placed crosswise

so that the one fits in a mortise in the middle of the other, and the

other likewise fits in the mortise of the first, thus making a kind of a

cross; these sills are three feet long and one foot wide and thick. The

crane-post is round at its upper end and is cut down to a depth of three

palms, and turns in a band fastened at each end to a roof-beam, from

which springs the inclined chimney wall. To the crane-post is affixed a

frame, which is made in this way: first, at a height of a cubit from the

bottom, is mortised into the crane-post a small cross-beam, a cubit and

three digits long, except its tenons, and two palms in width and

thickness. Then again, at a height of five feet above it, is another

small cross-beam of equal length, width, and thickness, mortised into

the crane-post. The other ends of these two small cross-beams are

mortised into an upright timber, six feet three palms long, and

three-quarters wide and thick; the mortise is transfixed by wooden pegs.

Above, at a height of three palms from the lower small cross-beam, are

two bars, one foot one palm long, not including the tenons, a palm three

digits wide, and a palm thick, which are mortised in the other sides of

the crane-post. In the same manner, under the upper small cross-beam are

two bars of the same size. Also in the upright timber there are mortised

the same number of bars, of the same length as the preceding, but three

digits thick, a palm two digits wide, the two lower ones being above the

lower small cross-beam. From the upright timber near the upper small

cross-beam, which at its other end is mortised into the crane-post, are

two mortised bars. On the outside of this frame, boards are fixed to the

small cross-beams, but the front and back parts of the frame have doors,

whose hinges are fastened to the boards which are fixed to the bars that

are mortised to the sides of the crane-post.

Then boards are laid upon the lower small cross-beam, and at a height of

two palms above these there is a small square iron axle, the sides of

which are two digits wide; both ends of it are round and turn in bronze

or iron bearings, one of these bearings being fastened in the

crane-post, the other in the upright timber. About each end of the small

axle is a wooden disc, of three palms and a digit radius and one palm

thick, covered on the rim with an iron band; these two discs are distant

two palms and as many digits from each other, and are joined with five

rundles; these rundles are two and a half digits thick and are placed

three digits apart. Thus a drum is made, which is a palm and a digit

distant from the upright timber, but further from the crane-post,

namely, a palm and three digits. At a height of a foot and a palm above

this little axle is a second small square iron axle, the thickness of

which is three digits; this one, like the first one, turns in bronze or

iron bearings. Around it is a toothed wheel, composed of two discs a

foot three palms in diameter, a palm and two digits thick; on the rim of

this there are twenty-three teeth, a palm wide and two digits thick;

they protrude a palm from the wheel and are three digits apart. And

around this same axle, at a distance of two palms and as many digits

toward the upright timber, is another disc of the same diameter as the

wheel and a palm thick; this turns in a hollowed-out place in the

upright timber. Between this disc and the disc of the toothed wheel

another drum is made, having likewise five rundles. There is, in

addition to this second axle, at a height of a cubit above it, a small

wooden axle, the journals of which are of iron; the ends are bound round

with iron rings so that the journals may remain firmly fixed, and the

journals, like the little iron axles, turn in bronze or iron bearings.

This third axle is at a distance of about a cubit from the upper small

cross-beam; it has, near the upright timber, a toothed wheel two and a

half feet in diameter, on the rim of which are twenty-seven teeth; the

other part of this axle, near the crane-post, is covered with iron

plates, lest it should be worn away by the chain which winds around it.

The end link of the chain is fixed in an iron pin driven into the little

axle; this chain passes out of the frame and turns over a little pulley

set between the beams of the crane-arm.

Above the frame, at a height of a foot and a palm, is the crane-arm.

This consists of two beams fifteen feet long, three palms wide, and two

thick, mortised into the crane-post, and they protrude a cubit from the

back of the crane-post and are fastened together. Moreover, they are

fastened by means of a wooden pin which penetrates through them and the

crane-post; this pin has at the one end a broad head, and at the other a

hole, through which is driven an iron bolt, so that the beams may be

tightly bound into the crane-post. The beams of the crane-arm are

supported and stayed by means of two oblique beams, six feet and two

palms long, and likewise two palms wide and thick; these are mortised

into the crane-post at their lower ends, and their upper ends are

mortised into the beams of the crane-arm at a point about four feet from

the crane-post, and they are fastened with iron nails. At the back of

the upper end of these oblique beams, toward the crane-post, is an iron

staple, fastened into the lower sides of the beams of the crane-arm, in

order that it may hold them fast and bind them. The outer end of each

beam of the crane-arm is set in a rectangular iron plate, and between

these are three rectangular iron plates, fixed in such a manner that the

beams of the crane-arm can neither move away from, nor toward, each

other. The upper sides of these crane-arm beams are covered with iron

plates for a length of six feet, so that a trolley can move on it.

The body of the trolley is made of wood from the Ostrya or any other

hard tree, and is a cubit long, a foot wide, and three palms thick; on

both edges of it the lower side is cut out to a height and width of a

palm, so that the remainder may move backward and forward between the

two beams of the crane-arm; at the front, in the middle part, it is cut

out to a width of two palms and as many digits, that a bronze pulley,

around a small iron axle, may turn in it. Near the corners of the

trolley are four holes, in which as many small wheels travel on the

beams of the crane-arm. Since this trolley, when it travels backward and

forward, gives out a sound somewhat similar to the barking of a dog, we

have given it this name[38]. It is propelled forward by means of a

crank, and is drawn back by means of a chain. There is an iron hook

whose ring turns round an iron pin fastened to the right side of the

trolley, which hook is held by a sort of clavis, which is fixed in the

right beam of the crane-arm.

At the end of the crane-post is a bronze pulley, the iron axle of which

is fastened in the beams of the crane-arm, and over which the chain

passes as it comes from the frame, and then, penetrating through the

hollow in the top of the trolley, it reaches to the little bronze pulley

of the trolley, and passing over this it hangs down. A hook on its end

engages a ring, in which are fixed the top links of three chains, each

six feet long, which pass through the three iron rings fastened in the

holes of the claves which are fixed into the middle iron band of the

dome, of which I have spoken.

Therefore when the master wishes to lift the dome by means of the crane,

the assistant fits over the lower small iron axle an iron crank, which

projects from the upright beam a palm and two digits; the end of the

little axle is rectangular, and one and a half digits wide and one digit

thick; it is set into a similar rectangular hole in the crank, which is

two digits long and a little more than a digit wide. The crank is

semi-circular, and one foot three palms and two digits long, as many

digits wide, and one digit thick. Its handle is straight and round, and

three palms long, and one and a half digits thick. There is a hole in

the end of the little axle, through which an iron pin is driven so that

the crank may not come off. The crane having four drums, two of which

are rundle-drums and two toothed-wheels, is more easily moved than

another having two drums, one of which has rundles and the other teeth.

Many, however, use only a simple contrivance, the pivots of whose

crane-post turn in the same manner, the one in an iron socket, the other

in a ring. There is a crane-arm on the crane-post, which is supported by

an oblique beam; to the head of the crane-arm a strong iron ring is

fixed, which engages a second iron ring. In this iron ring a strong

wooden lever-bar is fastened firmly, the head of which is bound by a

third iron ring, from which hangs an iron hook, which engages the rings

at the ends of the chains from the dome. At the other end of the

lever-bar is another chain, which, when it is pulled down, raises the

opposite end of the bar and thus the dome; and when it is relaxed the

dome is lowered.

[Illustration 481 (Cupellation Furnace at Freiberg): A--Chamber of the

furnace. B--Its bed. C--Passages. D--Rammer. E--Mallet. F--Artificer

making tubes from litharge according to the Roman method. G--Channel.

H--Litharge. I--Lower crucible or hearth. K--Stick. L--Tubes.]

In certain places, as at Freiberg in Meissen, the upper part of the

cupellation furnace is vaulted almost like an oven. This chamber is four

feet high and has either two or three apertures, of which the first, in

front, is one and a half feet high and a foot wide, and out of this

flows the litharge; the second aperture and likewise the third, if there

be three, are at the sides, and are a foot and a half high and two and a

half feet wide, in order that he who prepares the crucible may be able

to creep into the furnace. Its circular bed is made of cement, it has

two passages two feet high and one foot wide, for letting out the

vapour, and these lead directly through from one side to the other, so

that the one passage crosses the other at right angles, and thus four

openings are to be seen; these are covered at the top by rocks, wide,

but only a palm thick. On these and on the other parts of the interior

of the bed made of cement, is placed lute mixed with straw, to a depth

of three digits, as it was placed over the sole and the plates of copper

and the rocks of that other furnace. This, together with the ashes which

are thrown in, the master or the assistant, who, upon his knees,

prepares the crucible, tamps down with short wooden rammers and with

mallets likewise made of wood.

[Illustration 482 (Cupellation Furnace in Poland): A--Furnace similar to

an oven. B--Passage. C--Iron bars. D--Hole through which the litharge is

drawn out. E--Crucible which lacks a dome. F--Thick sticks. G--Bellows.]

The cupellation furnace in Poland and Hungary is likewise vaulted at

the top, and is almost similar to an oven, but in the lower part the bed

is solid, and there is no opening for the vapours, while on one side of

the crucible is a wall, between which and the bed of the crucible is a

passage in place of the opening for vapours; this passage is covered by

iron bars or rods extending from the wall to the crucible, and placed a

distance of two digits from each other. In the crucible, when it is

prepared, they first scatter straw, and then they lay in it cakes of

silver-lead alloy, and on the iron bars they lay wood, which when

kindled heats the crucible. They melt cakes to the weight of sometimes

eighty _centumpondia_ and sometimes a hundred _centumpondia_[39]. They

stimulate a mild fire by means of a blast from the bellows, and throw on

to the bars as much wood as is required to make a flame which will reach

into the crucible, and separate the lead from the silver. The litharge

is drawn out on the other side through an aperture that is just wide

enough for the master to creep through into the crucible. The Moravians

and Carni, who very rarely make more than a _bes_ or five-sixths of a

_libra_ of silver, separate the lead from it, neither in a furnace

resembling an oven, nor in the crucible covered by a dome, but on a

crucible which is without a cover and exposed to the wind; on this

crucible they lay cakes of silver-lead alloy, and over them they place

dry wood, and over these again thick green wood. The wood having been

kindled, they stimulate the fire by means of a bellows.

[Illustration 484 (Refining Silver): A--Pestle with teeth. B--Pestle

without teeth. C--Dish or tray full of ashes. D--Prepared tests placed

on boards or shelves. E--Empty tests. F--Wood. G--Saw.]

[Illustration 485 (Refining Silver): A--Straight knife having wooden

handles. B--Curved knife likewise having wooden handles. C--Curved knife

without wooden handles. D--Sieve. E--Balls. F--Iron door which the

master lets down when he refines silver, lest the heat of the fire

should injure his eyes. G--Iron implement on which the wood is placed

when the liquid silver is to be refined. H--Its other part passing

through the ring of another iron implement enclosed in the wall of the

furnace. I--Tests in which burning charcoal has been thrown.]

I have explained the method of separating lead from gold or silver. Now

I will speak of the method of refining silver, for I have already

explained the process for refining gold. Silver is refined in a refining

furnace, over whose hearth is an arched chamber built of bricks; this

chamber in the front part is three feet high. The hearth itself is five

feet long and four wide. The walls are unbroken along the sides and

back, but in front one chamber is placed over the other, and above these

and the wall is the upright chimney. The hearth has a round pit, a cubit

wide and two palms deep, into which are thrown sifted ashes, and in this

is placed a prepared earthenware "test," in such a manner that it is

surrounded on all sides by ashes to a height equal to its own. The

earthenware test is filled with a powder consisting of equal portions of

bones ground to powder, and of ashes taken from the crucible in which

lead is separated from gold or silver; others mix crushed brick with the

ashes, for by this method the powder attracts no silver to itself. When

the powder has been made up and moistened with water, a little is thrown

into the earthenware test and tamped with a wooden pestle. This pestle

is round, a foot long, and a palm and a digit wide, out of which extend

six teeth, each a digit thick, and a digit and a third long and wide,

and almost a digit apart; these six teeth form a circle, and in the

centre of them is the seventh tooth, which is round and of the same

length as the others, but a digit and a half thick; this pestle tapers a

little from the bottom up, that the upper part of the handle may be

round and three digits thick. Some use a round pestle without teeth.

Then a little powder is again moistened, and thrown into the test, and

tamped; this work is repeated until the test is entirely full of the

powder, which the master then cuts out with a knife, sharp on both

sides, and turned upward at both ends so that the central part is a palm

and a digit long; therefore it is partly straight and partly curved. The

blade is one and a half digits wide, and at each end it turns upward two

palms, which ends to the depth of a palm are either not sharpened or

they are enclosed in wooden handles. The master holds the knife with one

hand and cuts out the powder from the test, so that it is left three

digits thick all round; then he sifts the powder of dried bones over it

through a sieve, the bottom of which is made of closely-woven bristles.

Afterward a ball made of very hard wood, six digits in diameter, is

placed in the test and rolled about with both hands, in order to make

the inside even and smooth; for that matter he may move the ball about

with only one hand. The tests[40] are of various capacities, for some of

them when prepared hold much less than fifteen _librae_ of silver,

others twenty, some thirty, others forty, and others fifty. All these

tests thus prepared are dried in the sun, or set in a warm and covered

place; the more dry and old they are the better. All of them, when used

for refining silver, are heated by means of burning charcoal placed in

them. Others use instead of these tests an iron ring; but the test is

more useful, for if the powder deteriorates the silver remains in it,

while there being no bottom to the ring, it falls out; besides, it is

easier to place in the hearth the test than the iron ring, and

furthermore it requires much less powder. In order that the test should

not break and damage the silver, some bind it round with an iron band.

[Illustration 486 (Refining Silver): A--Grate. B--Brass block. C--Block

of wood. D--Cakes of silver. E--Hammer. F--Block of wood channelled in

the middle. G--Bowl full of holes. H--Block of wood fastened to an iron

implement. I--Fir-wood. K--Iron bar. L--Implement with a hollow end. The

implement which has a circular end is shown in the next picture.

M--Implement, the extremity of which is bent upwards. N--Implement in

the shape of tongs.]

In order that they may be more easily broken, the silver cakes are

placed upon an iron grate by the refiner, and are heated by burning

charcoal placed under them. He has a brass block two palms and two

digits long and wide, with a channel in the middle, which he places upon

a block of hard wood. Then with a double-headed hammer, he beats the hot

cakes of silver placed on the brass block, and breaks them in pieces.

The head of this hammer is a foot and two digits long, and a palm wide.

Others use for this purpose merely a block of wood channelled in the

top. While the fragments of the cake are still hot, he seizes them with

the tongs and throws them into a bowl with holes in the bottom, and

pours water over them. When the fragments are cooled, he puts them

nicely into the test by placing them so that they stand upright and

project from the test to a height of two palms, and lest one should fall

against the other, he places little pieces of charcoal between them;

then he places live charcoal in the test, and soon two twig basketsful

of charcoal. Then he blows in air with the bellows. This bellows is

double, and four feet two palms long, and two feet and as many palms

wide at the back; the other parts are similar to those described in Book

VII. The nozzle of the bellows is placed in a bronze pipe a foot long,

the aperture in this pipe being a digit in diameter in front and quite

round, and at the back two palms wide. The master, because he needs for

the operation of refining silver a fierce fire, and requires on that

account a vigorous blast, places the bellows very much inclined, in

order that, when the silver has melted, it may blow into the centre of

the test. When the silver bubbles, he presses the nozzle down by means

of a small block of wood moistened with water and fastened to an iron

rod, the outer end of which bends upward. The silver melts when it has

been heated in the test for about an hour; when it is melted, he removes

the live coals from the test and places over it two billets of fir-wood,

a foot and three palms long, a palm two digits wide, one palm thick at

the upper part, and three digits at the lower. He joins them together at

the lower edges, and into the billets he again throws the coals, for a

fierce fire is always necessary in refining silver. It is refined in two

or three hours, according to whether it was pure or impure, and if it is

impure it is made purer by dropping granulated copper or lead into the

test at the same time. In order that the refiner may sustain the great

heat from the fire while the silver is being refined, he lets down an

iron door, which is three feet long and a foot and three palms high;

this door is held on both ends in iron plates, and when the operation is

concluded, he raises it again with an iron shovel, so that its edge

holds against the iron hook in the arch, and thus the door is held open.

When the silver is nearly refined, which may be judged by the space of

time, he dips into it an iron bar, three and a half feet long and a

digit thick, having a round steel point. The small drops of silver that

adhere to the bar he places on the brass block and flattens with a

hammer, and from their colour he decides whether the silver is

sufficiently refined or not. If it is thoroughly purified it is very

white, and in a _bes_ there is only a _drachma_ of impurities. Some

ladle up the silver with a hollow iron implement. Of each _bes_ of

silver one _sicilicus_ is consumed, or occasionally when very impure,

three _drachmae_ or half an _uncia_[41].

[Illustration 488 (Cleansing of Silver Cakes): A--Implement with a ring.

B--Ladle. C--Its hole. D--Pointed bar. E--Forks. F--Cake of silver laid

upon the implement shaped like tongs. G--Tub of water. H--Block of wood,

with a cake laid upon it. I--Hammer. K--Silver again placed upon the

implement resembling tongs. L--Another tub full of water. M--Brass

wires. N--Tripod. O--Another block. P--Chisel. Q--Crucible of the

furnace. R--Test still smoking.]

The refiner governs the fire and stirs the molten silver with an iron

implement, nine feet long, a digit thick, and at the end first curved

toward the right, then curved back in order to form a circle, the

interior of which is a palm in diameter; others use an iron implement,

the end of which is bent directly upward. Another iron implement has the

shape of tongs, with which, by compressing it with his hands, he seizes

the coals and puts them on or takes them off; this is two feet long, one

and a half digits wide, and the third of a digit thick.

When the silver is seen to be thoroughly refined, the artificer removes

the coals from the test with a shovel. Soon afterward he draws water in

a copper ladle, which has a wooden handle four feet long; it has a small

hole at a point half-way between the middle of the bowl and the edge,

through which a hemp seed just passes. He fills this ladle three times

with water, and three times it all flows out through the hole on to the

silver, and slowly quenches it; if he suddenly poured much water on it,

it would burst asunder and injure those standing near. The artificer has

a pointed iron bar, three feet long, which has a wooden handle as many

feet long, and he puts the end of this bar into the test in order to

stir it. He also stirs it with a hooked iron bar, of which the hook is

two digits wide and a palm deep, and the iron part of its handle is

three feet long and the wooden part the same. Then he removes the test

from the hearth with a shovel or a fork, and turns it over, and by this

means the silver falls to the ground in the shape of half a sphere; then

lifting the cake with a shovel he throws it into a tub of water, where

it gives out a great sound. Or else, having lifted the cake of silver

with a fork, he lays it upon the iron implement similar to tongs, which

are placed across a tub full of water; afterward, when cooled, he takes

it from the tub again and lays it on the block made of hard wood and

beats it with a hammer, in order to break off any of the powder from the

test which adheres to it. The cake is then placed on the implement

similar to tongs, laid over the tub full of water, and cleaned with a

bundle of brass wire dipped into the water; this operation of beating

and cleansing is repeated until it is all clean. Afterward he places it

on an iron grate or tripod; the tripod is a palm and two digits high,

one and a half digits wide, and its span is two palms wide; then he puts

burning charcoal under the tripod or grate, in order again to dry the

silver that was moistened by the water. Finally, the Royal Inspector[42]

in the employment of the King or Prince, or the owner, lays the silver

on a block of wood, and with an engraver's chisel he cuts out two small

pieces, one from the under and the other from the upper side. These are

tested by fire, in order to ascertain whether the silver is thoroughly

refined or not, and at what price it should be sold to the merchants.

Finally he impresses upon it the seal of the King or the Prince or the

owner, and, near the same, the amount of the weight.

[Illustration 489 (Refining Silver): A--Muffle. B--Its little windows.

C--Its little bridge. D--Bricks. E--Iron door. F--Its little window.

G--Bellows. H--Hammer-chisel. I--Iron ring which some use instead of the

test. K--Pestle with which the ashes placed in the ring are pounded.]

There are some who refine silver in tests placed under iron or

earthenware muffles. They use a furnace, on the hearth of which they

place the test containing the fragments of silver, and they place the

muffle over it; the muffle has small windows at the sides, and in front

a little bridge. In order to melt the silver, at the sides of the muffle

are laid bricks, upon which the charcoal is placed, and burning

firebrands are put on the bridge. The furnace has an iron door, which is

covered on the side next to the fire with lute in order that it may not

be injured. When the door is closed it retains the heat of the fire, but

it has a small window, so that the artificers may look into the test and

may at times stimulate the fire with the bellows. Although by this

method silver is refined more slowly than by the other, nevertheless it

is more useful, because less loss is caused, for a gentle fire consumes

fewer particles than a fierce fire continually excited by the blast of

the bellows. If, on account of its great size, the cake of silver can be

carried only with difficulty when it is taken out of the muffle, they

cut it up into two or three pieces while it is still hot, with a wedge

or a hammer-chisel; for if they cut it up after it has cooled, little

pieces of it frequently fly off and are lost.

END OF BOOK X.

FOOTNOTES:

[1] _Vile a precioso_.

[2] The reagents mentioned in this Book are much the same as those of

Book VII, where (p. 220) a table is given showing the Latin and Old

German terms. Footnotes in explanation of our views as to these

substances may be most easily consulted through the index.

[3] _Aqua valens_, literally strong, potent, or powerful water. It will

appear later, from the method of manufacture, that hydrochloric, nitric,

and sulphuric acids and _aqua regia_ were more or less all produced and

all included in this term. We have, therefore, used either the term

_aqua valens_ or simply _aqua_ as it occurs in the text. The terms _aqua

fortis_ and _aqua regia_ had come into use prior to Agricola, but he

does not use them; the Alchemists used various terms, often _aqua

dissolvia_. It is apparent from the uses to which this reagent was put

in separating gold and silver, from the method of clarifying it with

silver and from the red fumes, that Agricola could have had practical

contact only with nitric acid. It is probable that he has copied part of

the recipes for the compounds to be distilled from the Alchemists and

from such works as the _Probierbuechlein_. In any event he could not have

had experience with them all, for in some cases the necessary

ingredients for making nitric acid are not all present, and therefore

could be of no use for gold and silver separation. The essential

ingredients for the production of this acid by distillation, were

saltpetre, water, and either vitriol or alum. The other substances

mentioned were unnecessary, and any speculation as to the combinations

which would result, forms a useful exercise in chemistry, but of little

purpose here. The first recipe would no doubt produce hydrochloric acid.

[4] Agricola, in the _Interpretatio_, gives the German equivalent for

the Latin _aerugo_ as _Spanschgruen_--"because it was first brought to

Germany from Spain; foreigners call it _viride aeris_ (copper green)."

The English "verdigris" is a corruption of _vert de grice_. Both

verdigris and white lead were very ancient products, and they naturally

find mention together among the ancient authors. The earliest

description of the method of making is from the 3rd Century B.C., by

Theophrastus, who says (101-2): "But these are works of art, as is also

Ceruse (_psimythion_) to make which, lead is placed in earthen vessels

over sharp vinegar, and after it has acquired some thickness of a kind

of rust, which it commonly does in about ten days, they open the vessels

and scrape off, as it were, a kind of foulness; they then place the lead

over the vinegar again, repeating over and over again the same method of

scraping it till it is wholly dissolved; what has been scraped off they

then beat to powder and boil for a long time; and what at last subsides

to the bottom of the vessel is the white lead.... Also in a manner

somewhat resembling this, verdigris (_ios_) is made, for copper is

placed over lees of wine (grape refuse?), and the rust which it acquires

by this means is taken off for use. And it is by this means that the

rust which appears is produced." (Based on Hill's translation.)

Vitruvius (VII, 12), Dioscorides (V, 51), and Pliny (XXXIV, 26 and 54),

all describe the method of making somewhat more elaborately.

[5] _Amiantus_ (_Interpretatio_ gives _federwis_, _pliant_,

_salamanderhar_). From Agricola's elaborate description in _De Natura

Fossilium_ (p. 252) there can be no doubt that he means asbestos. This

mineral was well-known to the Ancients, and is probably earliest

referred to (3rd Century B.C.) by Theophrastus in the following passage

(29): "There is also found in the mines of Scaptesylae a stone, in its

external appearance somewhat resembling wood, on which, if oil be

poured, it burns; but when the oil is burnt away, the burning of the

stone ceases, as if it were in itself not liable to such accidents."

There can be no doubt that Strabo (X, 1) describes the mineral: "At

Carystus there is found in the earth a stone, which is combed like wool,

and woven, so that napkins are made of this substance, which, when

soiled, are thrown into the fire and cleaned, as in the washing of

linen." It is also described by Dioscorides (V, 113) and Pliny (XIX, 4).

Asbestos cloth has been found in Pre-Augustinian Roman tombs.

[6] This list of four recipes is even more obscure than the previous

list. If they were distilled, the first and second mixtures would not

produce nitric acid, although possibly some sulphuric would result. The

third might yield nitric, and the fourth _aqua regia_. In view of the

water, they were certainly not used as cements, and the first and second

are deficient in the vital ingredients.

[7] _Distillation_, at least in crude form, is very old. Aristotle

(_Meteorologica_, IV.) states that sweet water can be made by

evaporating salt-water and condensing the steam. Dioscorides and Pliny

both describe the production of mercury by distillation (note 58, p.

432). The Alchemists of the Alexandrian School, from the 1st to the 6th

Centuries, mention forms of imperfect apparatus--an ample discussion of

which may be found in Kopp, _Beitraege zur Geschichte der Chemie_,

Braunschweig, 1869, p. 217.

[8] It is desirable to note the contents of the residues in the retort,

for it is our belief that these are the materials to which the author

refers as "lees of the water which separates gold from silver," in many

places in Book VII. They would be strange mixtures of sodium, potassium,

aluminium sulphates, with silica, brickdust, asbestos, and various

proportions of undigested vitriol, salt, saltpetre, alum, iron oxides,

etc. Their effect must have been uncertain. Many old German metallurgies

also refer to the _Todenkopf der Scheidwasser_, among them the

_Probierbuechlein_ before Agricola, and after him Lazarus Ercker

(_Beschreibung Allerfuernemsten_, etc., Prague, 1574). See also note 16,

p. 234.

[9] This use of silver could apply to one purpose only, that is, the

elimination of minor amounts of hydrochloric from the nitric acid, the

former originating no doubt from the use of salt among the ingredients.

The silver was thus converted into a chloride and precipitated. This use

of a small amount of silver to purify the nitric acid was made by

metallurgists down to fairly recent times. Biringuccio (IV, 2) and

Lazarus Ercker (p. 71) both recommend that the silver be dissolved first

in a small amount of acid, and the solution poured into the

newly-manufactured supply. They both recommend preserving this

precipitate and its cupellation after melting with lead--which Agricola

apparently overlooked.

[10] In this description of parting by nitric acid, the author digresses

from his main theme on pages 444 and 445, to explain a method apparently

for small quantities where the silver was precipitated by copper, and to

describe another cryptic method of precipitation. These subjects are

referred to in notes 11 and 12 below. The method of parting set out here

falls into six stages: _a_--cupellation, _b_--granulation, _c_--solution

in acid, _d_--treatment of the gold residues, _e_--evaporation of the

solution, _f_--reduction of the silver nitrate. For nitric acid parting,

bullion must be free from impurities, which cupellation would ensure; if

copper were left in, it would have the effect he mentions if we

understand "the silver separated from the gold soon unites with it

again," to mean that the silver unites with the copper, for the copper

would go into solution and come down with the silver on evaporation.

Agricola does not specifically mention the necessity of an excess of

silver in this description, although he does so elsewhere, and states

that the ratio must be at least three parts silver to one part gold. The

first description of the solution of the silver is clear enough, but

that on p. 445 is somewhat difficult to follow, for the author states

that the bullion is placed in a retort with the acid, and that

distillation is carried on between each additional charge of acid. So

far as the arrangement of a receiver might relate to the saving of any

acid that came over accidentally in the boiling, it can be understood,

but to distill off much acid would soon result in the crystallization of

the silver nitrate, which would greatly impede the action of subsequent

acid additions, and finally the gold could not be separated from such

nitrate in the way described. The explanation may be (apart from

incidental evaporation when heating) that the acids used were very weak,

and that by the evaporation of a certain amount of water, not only was

the acid concentrated, but room was provided for the further charges.

The acid in the gold wash-water, mentioned in the following paragraph,

was apparently thus concentrated. The "glass" mentioned as being melted

with litharge, argols, nitre, etc., was no doubt the silver nitrate. The

precipitation of the silver from the solution as a chloride, by the use

of salt, so generally used during the 18th and 19th Centuries, was known

in Agricola's time, although he does not mention it. It is mentioned in

Geber and the _Probierbuechlein_. The clarity of the latter on the

subject is of some interest (p. 34a): "How to pulverise silver and again

make it into silver. Take the silver and dissolve it in water with the

_starckenwasser_, _aqua fort_, and when that is done, take the silver

water and pour it into warm salty water, and immediately the silver

settles to the bottom and becomes powder. Let it stand awhile until it

has well settled, then pour away the water from it and dry the

settlings, which will become a powder like ashes. Afterward one can

again make it into silver. Take the powder and put it on a _test_, and

add thereto the powder from the settlings from which the _aqua forte_

has been made, and add lead. Then if there is a great deal, blow on it

until the lead has incorporated itself ... blow it until it _plickt_

(_blickens_). Then you will have as much silver as before."

[11] The silver is apparently precipitated by the copper of the bowl. It

would seem that this method was in considerable use for small amounts of

silver nitrate in the 16th Century. Lazarus Ercker gives elaborate

directions for this method (_Beschreibung Allerfuernemsten_, etc.,

Prague, 1574, p. 77).

[12] We confess to a lack of understanding of this operation with leaves

of lead and copper.

[13] We do not understand this "appearance of black." If the nitrate

came into contact with organic matter it would, of course, turn black by

reduction of the silver, and sunlight would have the same effect.

[14] This would be equal to from 62 to 94 parts of copper in 1,000.

[15] As 144 _siliquae_ are 1 _uncia_, then 1/4 _siliqua_ in 8 _unciae_

would equal one part silver in 4,608 parts gold, or about 999.8 fine.

[16] The object of this treatment with sulphur and copper is to separate

a considerable portion of silver from low-grade bullion (_i.e._, silver

containing some gold), in preparation for final treatment of the richer

gold-silver alloy with nitric acid. Silver sulphide is created by adding

sulphur, and is drawn off in a silver-copper regulus. After the first

sentence, the author uses silver alone where he obviously means silver

"containing some gold," and further he speaks of the "gold lump"

(_massula_) where he likewise means a button containing a great deal of

silver. For clarity we introduced the term "regulus" for the Latin

_mistura_. The operation falls into six stages: _a_, granulation; _b_,

sulphurization of the granulated bullion; _c_, melting to form a

combination of the silver sulphide with copper into a regulus, an alloy

of gold and silver settling out; _d_, repetition of the treatment to

abstract further silver from the "lump;" _e_, refining the "lump" with

nitric acid; _f_, recovery of the silver from the regulus by addition of

lead, liquation and cupellation.

The use of a "circle of fire" secures a low temperature that would

neither volatilize the sulphur nor melt the bullion. The amount of

sulphur given is equal to a ratio of 48 parts bullion and 9 parts

sulphur. We are not certain about the translation of the paragraph in

relation to the proportion of copper added to the granulated bullion;

because in giving definite quantities of copper to be added in the

contingencies of various original copper contents in the bullion, it

would be expected that they were intended to produce some positive ratio

of copper and silver. However, the ratio as we understand the text in

various cases works out to irregular amounts, _i.e._, 48 parts of silver

to 16, 12.6, 24, 20.5, 20.8, 17.8, or 18 parts of copper. In order to

obtain complete separation there should be sufficient sulphur to have

formed a sulphide of the copper as well as of the silver, or else some

of the copper and silver would come down metallic with the "lump". The

above ratio of copper added to the sulphurized silver, in the first

instance would give about 18 parts of copper and 9 parts of sulphur to

48 parts of silver. The copper would require 4.5 parts of sulphur to

convert it into sulphide, and the silver about 7 parts, or a total of

11.5 parts required against 9 parts furnished. It is plain, therefore,

that insufficient sulphur is given. Further, the litharge would probably

take up some sulphur and throw down metallic lead into the "lump".

However, it is necessary that there should be some free metallics to

collect the gold, and, therefore, the separation could not be complete

in one operation. In any event, on the above ratios the "gold lump" from

the first operation was pretty coppery, and contained some lead and

probably a good deal of silver, because the copper would tend to

desulphurize the latter. The "powder" of glass-galls, salt, and litharge

would render the mass more liquid and assist the "gold lump" to separate

out.

The Roman silver _sesterce_, worth about 2-1/8 pence or 4.2 American

cents, was no doubt used by Agricola merely to indicate an infinitesimal

quantity. The test to be applied to the regulus by way of cupellation

and parting of a sample with nitric acid, requires no explanation. The

truth of the description as to determining whether the gold had settled

out, by using a chalked iron rod, can only be tested by actual

experiment. It is probable, however, that the sulphur in the regulus

would attack the iron and make it black. The re-melting of the regulus,

if some gold remains in it, with copper and "powder" without more

sulphur, would provide again free metallics to gather the remaining

gold, and by desulphurizing some silver this button would probably not

be very pure.

From the necessity for some free metallics besides the gold in the first

treatment, it will be seen that a repetition of the sulphur addition and

re-melting is essential gradually to enrich the "lump". Why more copper

is added is not clear. In the second melting, the ratio is 48 parts of

the "gold lump", 12 parts of sulphur and 12 parts copper. In this case

the added copper would require about 3 parts sulphur, and if we consider

the deficiency of sulphur in the first operations pertained entirely to

the copper, then about 2.5 parts would be required to make good the

shortage, or in other words the second addition of sulphur is

sufficient. In the final parting of the "lump" it will be noticed that

the author states that the silver ratio must be arranged as three of

silver to one of gold. As to the recovery of the silver from the

regulus, he states that 66 _librae_ of silver give 132 _librae_ of

_regulus_. To this, 500 _librae_ of lead are added, and it is melted in

the "second" furnace, and the litharge and hearth-lead made are

re-melted in the "first" furnace, the cakes made being again treated in

the "third" furnace to separate the copper and lead. The "first" is

usually the blast furnace, the "second" furnace is the cupellation

furnace, and the "third" the liquation furnace. It is difficult to

understand this procedure. The charge sent to the cupellation furnace

would contain between 3% and 5% copper, and between 3% and 5% sulphur.

However, possibly the sulphur and copper could be largely abstracted in

the skimmings from the cupellation furnace, these being subsequently

liquated in the "third" furnace. It may be noted that two whole lines

from this paragraph are omitted in the editions of _De Re Metallica_

after 1600. For historical note on sulphur separation see page 461.

[17] There can be no doubt that in most instances Agricola's _stibium_

is antimony sulphide, but it does not follow that it was the mineral

_stibnite_, nor have we considered it desirable to introduce the

precision of either of these modern terms, and have therefore retained

the Latin term where the sulphide is apparently intended. The use of

antimony sulphide to part silver from gold is based upon the greater

affinity of silver than antimony for sulphur. Thus the silver, as in the

last process, is converted into a sulphide, and is absorbed in the

regulus, while the metallic antimony alloys with the gold and settles to

the bottom of the pot. This process has several advantages over the

sulphurization with crude sulphur; antimony is a more convenient vehicle

of sulphur, for it saves the preliminary sulphurization with its

attendant difficulties of volatilization of the sulphur; it also saves

the granulation necessary in the former method; and the treatment of the

subsequent products is simpler. However, it is possible that the

sulphur-copper process was better adapted to bullion where the

proportion of gold was low, because the fineness of the bullion

mentioned in connection with the antimonial process was apparently much

higher than the previous process. For instance, a _bes_ of gold,

containing 5, 6, or 7 double _sextulae_ of silver would be .792, .750 or

.708 fine. The antimonial method would have an advantage over nitric

acid separation, in that high-grade bullion could be treated direct

without artificial decrease of fineness required by inquartation to

about .250 fine, with the consequent incidental losses of silver

involved.

The process in this description falls into six operations: _a_,

sulphurization of the silver by melting with antimony sulphide; _b_,

separation of the gold "lump" (_massula_) by jogging; _c_, re-melting

the regulus (_mistura_) three or four times for recovery of further

"lumps"; _d_, re-melting of the "lump" four times, with further

additions of antimony sulphide; _e_, cupellation of the regulus to

recover the silver; _f_, cupellation of the antimony from the "lump" to

recover the gold. Percy seems to think it difficult to understand the

insistence upon the addition of copper. Biringuccio (IV, 6) states,

among other things, that copper makes the ingredients more liquid. The

later metallurgists, however, such as Ercker, Lohneys, and Schlueter, do

not mention this addition; they do mention the "swelling and frothing,"

and recommend that the crucible should be only partly filled. As to the

copper, we suggest that it would desulphurize part of the antimony and

thus free some of that metal to collect the gold. If we assume bullion

of the medium fineness mentioned and containing no copper, then the

proportions in the first charge would be about 36 parts gold, 12 parts

silver, 41 parts sulphur, 103 parts antimony, and 9 parts copper. The

silver and copper would take up 4.25 parts of sulphur, and thus free

about 10.6 parts of antimony as metallics. It would thus appear that the

amount of metallics provided to assist the collection of the gold was

little enough, and that the copper in freeing 5.6 parts of the antimony

was useful. It appears to have been necessary to have a large excess of

antimony sulphide; for even with the great surplus in the first charge,

the reaction was only partial, as is indicated by the necessity for

repeated melting with further antimony.

The later metallurgists all describe the separation of the metallic

antimony from the gold as being carried out by oxidation of the

antimony, induced by a jet of air into the crucible, this being

continued until the mass appears limpid and no cloud forms in the

surface in cooling. Agricola describes the separation of the silver from

the regulus by preliminary melting with argols, glass-gall, and some

lead, and subsequent cupellation of the lead-silver alloy. The statement

that unless this preliminary melting is done, the cupel will absorb

silver, might be consonant with an attempt at cupellation of sulphides,

and it is difficult to see that much desulphurizing could take place

with the above fluxes. In fact, in the later descriptions of the

process, iron is used in this melting, and we are under the impression

that Agricola had omitted this item for a desulphurizing reagent. At the

Dresden Mint, in the methods described by Percy (Metallurgy Silver and

Gold, p. 373) the gold lumps were tested for fineness, and from this the

amount of gold retained in the regulus was computed. It is not clear

from Agricola's account whether the test with nitric acid was applied to

the regulus or to the "lumps". For historical notes see p. 461.

[18] As will be shown in the historical note, this process of separating

gold and silver is of great antiquity--in all probability the only

process known prior to the Middle Ages, and in any event, the first one

used. In general the process was performed by "cementing" the

disintegrated bullion with a paste and subjecting the mass to

long-continued heat at a temperature under the melting point of the

bullion. The cement (_compositio_) is of two different species; in the

first species saltpetre and vitriol and some aluminous or silicious

medium are the essential ingredients, and through them the silver is

converted into nitrate and absorbed by the mass; in the second species,

common salt and the same sort of medium are the essentials, and in this

case the silver is converted into a chloride. Agricola does not

distinguish between these two species, for, as shown by the text, his

ingredients are badly mixed.

The process as here described falls into five operations: _a_,

granulation of the bullion or preparation of leaves; _b_, heating

alternate layers of cement and bullion in pots; _c_, washing the gold to

free it of cement; _d_, melting the gold with borax or soda; _e_,

treatment of the cement by way of melting with lead and cupellation to

recover the silver. Investigation by Boussingault (_Ann. De Chimie_,

1833, p. 253-6), D'Elhuyar (_Bergbaukunde_, Leipzig, 1790, Vol. II, p.

200), and Percy (Metallurgy of Silver and Gold, p. 395), of the action

of common salt upon silver under cementation conditions, fairly well

demonstrated the reactions involved in the use of this species of

cement. Certain factors are essential besides salt: _a_, the admission

of air, which is possible through the porous pots used; _b_, the

presence of some moisture to furnish hydrogen; _c_, the addition of

alumina or silica. The first would be provided by Agricola in the use of

new pots, the second possibly by use of wood fuel in a closed furnace,

the third by the inclusion of brickdust. The alumina or silica at high

temperatures decomposes the salt, setting free hydrochloric acid and

probably also free chlorine. The result of the addition of vitriol in

Agricola's ingredients is not discussed by those investigators, but

inasmuch as vitriol decomposes into sulphuric acid under high

temperatures, this acid would react upon the salt to free hydrochloric

acid, and thus assist to overcome deficiencies in the other factors. It

is possible also that sulphuric acid under such conditions would react

directly upon the silver to form silver sulphates, which would be

absorbed into the cement. As nitric acid is formed by vitriol and

saltpetre at high temperatures, the use of these two substances as a

cementing compound would produce nitric acid, which would at once attack

the silver to form silver nitrate, which would be absorbed into the

melted cement. In this case the brickdust probably acted merely as a

vehicle for the absorption, and to lower the melting point of the mass

and prevent fusion of the metal. While nitric acid will only part gold

and silver when the latter is in great excess, yet when applied as fumes

under cementation conditions it appears to react upon a minor ratio of

silver. While the reactions of the two above species of compounds can be

accounted for in a general way, the problem furnished by Agricola's

statements is by no means simple, for only two of his compounds are

simply salt cements, the others being salt and nitre mixtures. An

inspection of these compounds produces at once a sense of confusion.

Salt is present in every compound, saltpetre in all but two, vitriol in

all but three. Lewis (_Traite Singulier de Metallique_, Paris, 1743, II,

pp. 48-60), in discussing these processes, states that salt and

saltpetre must never be used together, as he asserts that in this case

_aqua regia_ would be formed and the gold dissolved. Agricola, however,

apparently found no such difficulty. As to the other ingredients, apart

from nitre, salt, vitriol, and brickdust, they can have been of no use.

Agricola himself points out that ingredients of "metallic origin"

corrupt the gold and that brickdust and common salt are sufficient. In a

description of this process in the _Probierbuechlein_ (p. 58), no nitre

is mentioned. This booklet does mention the recovery of the silver from

the cement by amalgamation with mercury--the earliest mention of silver

amalgamation.

[19] While a substance which we now know to be natural zinc sulphate was

known to Agricola (see note 11, p. 572), it is hardly possible that it

is referred to here. If green vitriol be dehydrated and powdered, it is

white.

[20] The processes involved by these "other" compounds are difficult to

understand, because of the lack of information given as to the method of

operation. It might be thought that these were five additional recipes

for cementing pastes, but an inspection of their internal composition

soon dissipates any such assumption, because, apart from the lack of

brickdust or some other similar necessary ingredient, they all contain

more or less sulphur. After describing a preliminary treatment of the

bullion by cupellation, the author says: "Then the silver is sprinkled

with two _unciae_ of that powdered compound and is stirred. Afterward it

is poured into another crucible ... and violently shaken. The rest is

performed according to the process I have already explained." As he has

already explained four or five parting processes, it is not very clear

to which one this refers. In fact, the whole of this discussion reads as

if he were reporting hearsay, for it lacks in every respect the infinite

detail of his usual descriptions. In any event, if the powder was

introduced into the molten bullion, the effect would be to form some

silver sulphides in a regulus of different composition depending upon

the varied ingredients of different compounds. The enriched bullion was

settled out in a "lump" and treated "as I have explained," which is not

clear.

[21] HISTORICAL NOTE ON PARTING GOLD AND SILVER. Although the earlier

Classics contain innumerable references to refining gold and silver,

there is little that is tangible in them, upon which to hinge the

metallurgy of parting the precious metals. It appears to us, however,

that some ability to part the metals is implied in the use of the

touchstone, for we fail to see what use a knowledge of the ratio of gold

and silver in bullion could have been without the power to separate

them. The touchstone was known to the Greeks at least as early as the

5th Century B.C. (see note 37, p. 252), and a part of Theophrastus'

statement (LXXVIII.) on this subject bears repetition in this

connection: "The nature of the stone which tries gold is also very

wonderful, as it seems to have the same power as fire; which is also a

test of that metal.... The trial by fire is by the colour and the

quantity lost by it, but that of the stone is made only by rubbing,"

etc. This trial by fire certainly implies a parting of the metals. It

has been argued from the common use of _electrum_--a gold-silver

alloy--by the Ancients, that they did not know how to part the two

metals or they would not have wasted gold in such a manner, but it seems

to us that the very fact that _electrum_ was a positive alloy (20% gold,

80% silver), and that it was deliberately made (Pliny XXXIII, 23) and

held of value for its supposed superior brilliancy to silver and the

belief that goblets made of it detected poison, is sufficient answer to

this.

To arrive by a process of elimination, we may say that in the Middle

Ages, between 1100 and 1500 A.D., there were known four methods of

parting these metals: _a_, parting by solution in nitric acid; _b_,

sulphurization of the silver in finely-divided bullion by heating it

with sulphur, and the subsequent removal of the silver sulphide in a

regulus by melting with copper, iron, or lead; _c_, melting with an

excess of antimony sulphide, and the direct conversion of the silver to

sulphide and its removal in a regulus; _d_, cementation of the

finely-divided bullion with salt, and certain necessary collateral

re-agents, and the separation of the silver by absorption into the

cement as silver chloride. Inasmuch as it can be clearly established

that mineral acids were unknown to the Ancients, we can eliminate that

method. Further, we may say at once that there is not, so far as has yet

been found, even a remote statement that could be applied to the

sulphide processes. As to cementation with salt, however, we have some

data at about the beginning of the Christian Era.

Before entering into a more detailed discussion of the history of

various processes, it may be useful, in a word, to fix in the mind of

the reader our view of the first authority on various processes, and his

period.

(1) Separation by cementation with salt, Strabo (?) 63 B.C.-24

A.D.; Pliny 23-79 A.D.

(2) Separation by sulphur, Theophilus, 1150-1200 A.D.

(3) Separation by nitric acid, Geber, prior to 14th Century.

(4) Separation by antimony sulphide, Basil Valentine, end 14th

Century, or _Probierbuechlein_, beginning 15th Century.

(5) Separation by antimony sulphide and copper, or sulphur and

copper, _Probierbuechlein_, beginning 15th Century.

(6) Separation by cementation with saltpetre, Agricola, 1556.

(7) Separation by sulphur and iron, Schlueter, 1738.

(8) Separation by sulphuric acid, D'Arcet, 1802.

(9) Separation by chloride gas, Thompson, 1833.

(10) Separation electrolytically, latter part 19th Century.

PARTING BY CEMENTATION. The following passage from Strabo is of prime

interest as the first definite statement on parting of any kind (III, 2,

8): "That when they have melted the gold and purified it by means of a

kind of aluminous earth, the residue left is _electrum_. This, which

contains a mixture of silver and gold, being again subjected to the

fire, the silver is separated and the gold left (pure); for this metal

is easily dissipated and fat, and on this account gold is most easily

molten by straw, the flame of which is soft, and bearing a similarity

(to the gold) causes it easily to dissolve, whereas coal, besides

wasting a great deal, melts it too much, by reason of its vehemence, and

carries it off (in vapour)." This statement has provoked the liveliest

discussion, not only on account of the metallurgical interest and

obscurity, but also because of differences of view as to its

translation; we have given that of Mr. H. C. Hamilton (London, 1903). A

review of this discussion will be found in Percy's Metallurgy of Gold

and Silver, p. 399. That it refers to cementation at all hangs by a

slender thread, but it seems more nearly this than anything else.

Pliny (XXXIII, 25) is a little more ample: "(The gold) is heated with

double its weight of salt and thrice its weight of _misy_, and again

with two portions of salt and one of a stone which they call _schistos_.

The _virus_ is drawn out when these things are burnt together in an

earthen crucible, itself remaining pure and incorrupt, the remaining ash

being preserved in an earthen pot and mixed with water as a lotion for

_lichen_ (ring-worm) on the face." Percy (Metallurgy Silver and Gold, p.

398) rightly considers that this undoubtedly refers to the parting of

silver and gold by cementation with common salt. Especially as Pliny

further on states that with regard to _misy_, "In purifying gold they

mix it with this substance." There can be no doubt from the explanations

of Pliny and Dioscorides that _misy_ was an oxidized pyrite, mostly iron

sulphate. Assuming the latter case, then all of the necessary elements

of cementation, _i.e._, vitriol, salt, and an aluminous or silicious

element, are present.

The first entirely satisfactory evidence on parting is to be found in

Theophilus (12th Century), and we quote the following from Hendrie's

translation (p. 245): "Of Heating the Gold. Take gold, of whatsoever

sort it may be, and beat it until thin leaves are made in breadth three

fingers, and as long as you can. Then cut out pieces that are equally

long and wide and join them together equally, and perforate through all

with a fine cutting iron. Afterwards take two earthen pots proved in the

fire, of such size that the gold can lie flat in them, and break a tile

very small, or clay of the furnace burned and red, weigh it, powdered,

into two equal parts, and add to it a third part salt for the same

weight; which things being slightly sprinkled with urine, are mixed

together so that they may not adhere together, but are scarcely wetted,

and put a little of it upon a pot about the breadth of the gold, then a

piece of the gold itself, and again the composition, and again the gold,

which in the digestion is thus always covered, that gold may not be in

contact with gold; and thus fill the pot to the top and cover it above

with another pot, which you carefully lute round with clay, mixed and

beaten, and you place it over the fire, that it may be dried. In the

meantime compose a furnace from stones and clay, two feet in height, and

a foot and a half in breadth, wide at the bottom, but narrow at the top,

where there is an opening in the middle, in which project three long and

hard stones, which may be able to sustain the flame for a long time,

upon which you place the pots with the gold, and cover them with other

tiles in abundance. Then supply fire and wood, and take care that a

copious fire is not wanting for the space of a day and night. In the

morning taking out the gold, again melt, beat and place it in the

furnace as before. Again also, after a day and night, take it away and

mixing a little copper with it, melt it as before, and replace it upon

the furnace. And when you have taken it away a third time, wash and dry

it carefully, and so weighing it, see how much is wanting, then fold it

up and keep it."

The next mention is by Geber, of whose date and authenticity there is

great doubt, but, in any event, the work bearing his name is generally

considered to be prior to the 14th, although he has been placed as early

as the 8th Century. We quote from Russell's translation, pp. 17 and 224,

which we have checked with the Latin edition of 1542: "Sol, or gold, is

beaten into thin plates and with them and common salt very well prepared

lay upon lay in a vessel of calcination which set into the furnace and

calcine well for three days until the whole is subtily calcined. Then

take it out, grind well and wash it with vinegar, and dry it in the sun.

Afterwards grind it well with half its weight of cleansed

_sal-armoniac_; then set it to be dissolved until the whole be dissolved

into most clear water." Further on: "Now we will declare the way of

cementing. Seeing it is known to us that cement is very necessary in the

examen of perfection, we say it is compounded of inflammable things. Of

this kind are, all blackening, flying, penetrating, and burned things;

as is vitriol, _sal-armoniac_, _flos aeris_ (copper oxide scales) and

the ancient _fictile_ stone (earthen pots), and a very small quantity,

or nothing, of sulphur, and urine with like acute and penetrating

things. All these are impasted with urine and spread upon thin plates of

that body which you intend shall be examined by this way of probation.

Then the said plates must be laid upon a grate of iron included in an

earthen vessel, yet so as one touch not the other that the virtue of the

fire may have free and equal access to them. Thus the whole must be kept

in fire in a strong earthen vessel for the space of three days. But here

great caution is required that the plates may be kept but not melt."

Albertus Magnus (1205-1280) _De Mineralibus et Rebus Metallicis_, Lib.

IV, describes the process as follows:--"But when gold is to be purified

an earthen vessel is made like a cucurbit or dish, and upon it is placed

a similar vessel; and they are luted together with the tenacious lute

called by alchemists the lute of wisdom. In the upper vessel there are

numerous holes by which vapour and smoke may escape; afterwards the gold

in the form of short thin leaves is arranged in the vessel, the leaves

being covered consecutively with a mixture obtained by mixing together

soot, salt, and brick dust; and the whole is strongly heated until the

gold becomes perfectly pure and the base substances with which it was

mixed are consumed." It will be noted that salt is the basis of all

these cement compounds. We may also add that those of Biringuccio and

all other writers prior to Agricola were of the same kind, our author

being the first to mention those with nitre.

PARTING WITH NITRIC ACID. The first mention of nitric acid is in

connection with this purpose, and, therefore, the early history of this

reagent becomes the history of the process. Mineral acids of any kind

were unknown to the Greeks or Romans. The works of the Alchemists and

others from the 12th to the 15th Centuries, have been well searched by

chemical historians for indications of knowledge of the mineral acids,

and many of such suspected indications are of very doubtful order. In

any event, study of the Alchemists for the roots of chemistry is fraught

with the greatest difficulty, for not only is there the large ratio of

fraud which characterised their operations, but there is even the much

larger field of fraud which characterised the authorship and dates of

writing attributed to various members of the cult. The mention of

saltpetre by Roger Bacon (1214-94), and Albertus Magnus (1205-80), have

caused some strain to read a knowledge of mineral acids into their

works, but with doubtful result. Further, the Monk Theophilus

(1150-1200) is supposed to have mentioned products which would be

mineral acids, but by the most careful scrutiny of that work we have

found nothing to justify such an assertion, and it is of importance to

note that as Theophilus was a most accomplished gold and silver worker,

his failure to mention it is at least evidence that the process was not

generally known. The transcribed manuscripts and later editions of such

authors are often altered to bring them "up-to-date." The first mention

is in the work attributed to Geber, as stated above, of date prior to

the 14th Century. The following passage from his _De Inventione

Veritatis_ (Nuremberg edition, 1545, p. 182) is of interest:--"First

take one _libra_ of vitriol of Cyprus and one-half _libra_ of saltpetre

and one-quarter of alum of Jameni, extract the _aqua_ with the redness

of the alembic--for it is very solvative--and use as in the foregoing

chapters. This can be made acute if in it you dissolve a quarter of

sal-ammoniac, which dissolves gold, sulphur, and silver." Distilling

vitriol, saltpetre and alum would produce nitric acid. The addition of

sal-ammoniac would make _aqua regia_; Geber used this solvent

water--probably without being made "more acute"--to dissolve silver, and

he crystallized out silver nitrate. It would not be surprising to find

all the Alchemists subsequent to Geber mentioning acids. It will thus be

seen that even the approximate time at which the mineral-acids were

first made cannot be determined, but it was sometime previous to the

15th Century, probably not earlier than the 12th Century. Beckmann

(Hist. of Inventions II, p. 508) states that it appears to have been an

old tradition that acid for separating the precious metals was first

used at Venice by some Germans; that they chiefly separated the gold

from Spanish silver and by this means acquired great riches. Beckmann

considers that the first specific description of the process seems to be

in the work of William Budaeus (_De Asse_, 1516, III, p. 101), who

speaks of it as new at this time. He describes the operation of one, Le

Conte, at Paris, who also acquired a fortune through the method.

Beckmann and others have, however, entirely overlooked the early

_Probierbuechlein_. If our conclusions are correct that the first of

these began to appear at about 1510, then they give the first

description of inquartation. This book (see appendix) is made up of

recipes, like a cook-book, and four or five different recipes are given

for this purpose; of these we give one, which sufficiently indicates a

knowledge of the art (p. 39): "If you would part them do it this way:

Beat the silver which you suppose to contain gold, as thin as possible;

cut it in small pieces and place it in 'strong' water (_starkwasser_).

Put it on a mild fire till it becomes warm and throws up blisters or

bubbles. Then take it and pour off the water into a copper-bowl; let it

stand and cool. Then the silver settles itself round the copper bowl;

let the silver dry in the copper bowl, then pour the water off and melt

the silver in a crucible. Then take the gold also out of the glass

_kolken_ and melt it together." Biringuccio (1540, Book VI.) describes

the method, but with much less detail than Agricola. He made his acid

from alum and saltpetre and calls it _lacque forti_.

PARTING WITH SULPHUR. This process first appears in Theophilus

(1150-1200), and in form is somewhat different from that mentioned by

Agricola. We quote from Hendrie's Translation, p. 317, "How gold is

separated from silver. When you have scraped the gold from silver, place

this scraping in a small cup in which gold or silver is accustomed to be

melted, and press a small linen cloth upon it, that nothing may by

chance be abstracted from it by the wind of the bellows, and placing it

before the furnace, melt it; and directly lay fragments of sulphur in

it, according to the quantity of the scraping, and carefully stir it

with a thin piece of charcoal until its fumes cease; and immediately

pour it into an iron mould. Then gently beat it upon the anvil lest by

chance some of that black may fly from it which the sulphur has burnt,

because it is itself silver. For the sulphur consumes nothing of the

gold, but the silver only, which it thus separates from the gold, and

which you will carefully keep. Again melt this gold in the same small

cup as before, and add sulphur. This being stirred and poured out, break

what has become black and keep it, and do thus until the gold appear

pure. Then gather together all that black, which you have carefully

kept, upon the cup made from the bone and ash, and add lead, and so burn

it that you may recover the silver. But if you wish to keep it for the

service of niello, before you burn it add to it copper and lead,

according to the measure mentioned above, and mix with sulphur." This

process appears in the _Probierbuechlein_ in many forms, different

recipes containing other ingredients besides sulphur, such as salt,

saltpetre, sal-ammoniac, and other things more or less effective. In

fact, a series of hybrid methods between absolute melting with sulphur

and cementation with salt, were in use, much like those mentioned by

Agricola on p. 458.

PARTING WITH ANTIMONY SULPHIDE. The first mention of this process lies

either in Basil Valentine's "Triumphant Chariot of Antimony" or in the

first _Probierbuechlein_. The date to be assigned to the former is a

matter of great doubt. It was probably written about the end of the 15th

Century, but apparently published considerably later. The date of the

_Probierbuechlein_ we have referred to above. The statement in the

"Triumphal Chariot" is as follows (Waite's Translation, p. 117-118):

"The elixir prepared in this way has the same power of penetrating and

pervading the body with its purifying properties that antimony has of

penetrating and purifying gold.... This much, however, I have proved

beyond a possibility of doubt, that antimony not only purifies gold and

frees it from foreign matter, but it also ameliorates all other metals,

but it does the same for animal bodies." There are most specific

descriptions of this process in the other works attributed to Valentine,

but their authenticity is so very doubtful that we do not quote. The

_Probierbuechlein_ gives several recipes for this process, all to the

same metallurgical effect, of which we quote two: "How to separate

silver from gold. Take 1 part of golden silver, 1 part of _spiesglass_,

1 part copper, 1 part lead; melt them together in a crucible. When

melted pour into the crucible pounded sulphur and directly you have

poured it in cover it up with soft lime so that the fumes cannot escape,

and let it get cold and you will find your gold in a button. Put that

same in a pot and blow on it." "How to part gold and silver by melting

or fire. Take as much gold-silver as you please and granulate it; take 1

_mark_ of these grains, 1 _mark_ of powder; put them together in a

crucible. Cover it with a small cover, put it in the fire, and let it

slowly heat; blow on it gently until it melts; stir it all well together

with a stick, pour it out into a mould, strike the mould gently with a

knife so that the button may settle better, let it cool, then turn the

mould over, strike off the button and twice as much _spiesglas_ as the

button weighs, put them in a crucible, blow on it till it melts, then

pour it again into a mould and break away the button as at first. If you

want the gold to be good always add to the button twice as much

_spiesglass_. It is usually good gold in three meltings. Afterward take

the button, place it on a cupel, blow on it till it melts. And if it

should happen that the gold is covered with a membrane, then add a very

little lead, then it shines (_plickt_) and becomes clearer." Biringuccio

(1540) also gives a fairly clear exposition of this method. All the old

refiners varied the process by using mixtures of salt, antimony

sulphide, and sulphur, in different proportions, with and without lead

or copper; the net effect was the same. Later than Agricola these

methods of parting bullion by converting the silver into a sulphide and

carrying it off in a regulus took other forms. For instance, Schlueter

(_Huette-Werken_, Braunschweig, 1738) describes a method by which, after

the granulated bullion had been sulphurized by cementation with sulphur

in pots, it was melted with metallic iron. Lampadius (_Grundriss Einer

Allgemeinen Huettenkunde_, Goettingen, 1827) describes a treatment of the

bullion, sulphurized as above, with litharge, thus creating a

lead-silver regulus and a lead-silver-gold bullion which had to be

repeatedly put through the same cycle. The principal object of these

processes was to reduce silver bullion running low in gold to a ratio

acceptable for nitric acid treatment.

Before closing the note on the separation of gold and silver, we may add

that with regard to the three processes largely used to-day, the

separation by solution of the silver from the bullion by concentrated

sulphuric acid where silver sulphate is formed, was first described by

D'Arcet, Paris, in 1802; the separation by introducing chlorine gas into

the molten bullion and thus forming silver chlorides was first described

by Lewis Thompson in a communication to the Society of Arts, 1833, and

was first applied on a large scale by F. B. Miller at the Sydney Mint in

1867-70; we do not propose to enter into the discussion as to who is the

inventor of electrolytic separation.

[22] There were three methods of gilding practised in the Middle

Ages--the first by hammering on gold leaf; the second by laying a thin

plate of gold on a thicker plate of silver, expanding both together, and

fabricating the articles out of the sheets thus prepared; and the third

by coating over the article with gold amalgam, and subsequently driving

off the mercury by heat. Copper and iron objects were silver-plated by

immersing them in molten silver after coating with sal-ammoniac or

borax. Tinning was done in the same way.

[23] See note 12, p. 297, for complete discussion of amalgamation.

[24] These nine methods of separating gold from copper are based

fundamentally upon the sulphur introduced in each case, whereby the

copper is converted into sulphides and separated off as a matte. The

various methods are much befogged by the introduction of extraneous

ingredients, some of which serve as fluxes, while others would provide

metallics in the shape of lead or antimony for collection of the gold,

but others would be of no effect, except to increase the matte or slag.

Inspection will show that the amount of sulphur introduced in many

instances is in so large ratio that unless a good deal of volatilization

took place there would be insufficient metallics to collect the gold, if

it happened to be in small quantities. In a general way the auriferous

button is gradually impoverished in copper until it is fit for

cupellation with lead, except in one case where the final stage is

accomplished by amalgamation. The lore of the old refiners was much

after the order of that of modern cooks--they treasured and handed down

various efficacious recipes, and of those given here most can be found

in identical terms in the _Probierbuechlein_, some editions of which, as

mentioned before, were possibly fifty years before _De Re Metallica_.

This knowledge, no doubt, accumulated over long experience; but, so far

as we are aware, there is no description of sulphurizing copper for this

purpose prior to the publication mentioned.

[25] _Sal artificiosus_. The compound given under this name is of quite

different ingredients from the stock fluxes given in Book VII under the

same term. The method of preparation, no doubt, dehydrated this one; it

would, however, be quite effective for its purpose of sulphurizing the

copper. There is a compound given in the _Probierbuechlein_ identical

with this, and it was probably Agricola's source of information.

[26] Throughout the book the cupellation furnace is styled the _secunda

fornax_ (Glossary, _Treibeherd_). Except in one or two cases, where

there is some doubt as to whether the author may not refer to the second

variety of blast furnace, we have used "cupellation furnace." Agricola's

description of the actual operation of the old German cupellation is

less detailed than that of such authors as Schlueter (_Huette-Werken_,

Braunschweig, 1738) or Winkler (_Beschreibung der Freyberger Schmelz

Huttenprozesse_, Freyberg, 1837). The operation falls into four periods.

In the first period, or a short time after melting, the first scum--the

_abzug_--arises. This material contains most of the copper, iron, zinc,

or sulphur impurities in the lead. In the second period, at a higher

temperature, and with the blast turned on, a second scum arises--the

_abstrich_. This material contains most of the antimony and arsenical

impurities. In the third stage the litharge comes over. At the end of

this stage the silver brightens--"_blicken_"--due to insufficient

litharge to cover the entire surface. Winkler gives the following

average proportion of the various products from a charge of 100

_centners_:--

_Abzug_ 2 _centners_, containing 64% lead

_Abstrich_ 5-1/2 " " 73% "

_Herdtplei_ 21-1/2 " " 60% "

Impure litharge 18 " " 85% "

Litharge 66 " " 89% "

---

Total 113 _centners_

He estimates the lead loss at from 8% to 15%, and gives the average

silver contents of _blicksilber_ as about 90%. Many analyses of the

various products may be found in Percy (Metallurgy of Lead, pp.

198-201), Schnabel and Lewis (Metallurgy, Vol. I, p. 581); but as they

must vary with every charge, a repetition of them here is of little

purpose.

HISTORICAL NOTE ON CUPELLATION. The cupellation process is of great

antiquity, and the separation of silver from lead in this manner very

probably antedates the separation of gold and silver. We can be certain

that the process has been used continuously for at least 2,300 years,

and was only supplanted in part by Pattinson's crystallization process

in 1833, and further invaded by Parks' zinc method in 1850, and during

the last fifteen years further supplanted in some works by electrolytic

methods. However, it yet survives as an important process. It seems to

us that there is no explanation possible of the recovery of the large

amounts of silver possessed from the earliest times, without assuming

reduction of that metal with lead, and this necessitates cupellation. If

this be the case, then cupellation was practised in 2500 B.C. The

subject has been further discussed on p. 389. The first direct evidence

of the process, however, is from the remains at Mt. Laurion (note 6, p.

27), where the period of greatest activity was at 500 B.C., and it was

probably in use long before that time. Of literary evidences, there are

the many metaphorical references to "fining silver" and "separating

dross" in the Bible, such as Job (XXVIII, 1), Psalms (XII, 6, LXVI, 10),

Proverbs (XVII, 3). The most certain, however, is Jeremiah (VI, 28-30):

"They are all brass [_sic_] and iron; they are corrupters. The bellows

are burned, the lead is consumed in the fire, the founder melteth in

vain; for the wicked are not plucked away. Reprobate silver shall men

call them." Jeremiah lived about 600 B.C. His contemporary Ezekiel

(XXII, 18) also makes remark: "All they are brass and tin and iron and

lead in the midst of the furnace; they are even the dross of the

silver." Among Greek authors Theognis (6th century B.C.) and Hippocrates

(5th century B.C.) are often cited as mentioning the refining of gold

with lead, but we do not believe their statements will stand this

construction without strain. Aristotle (Problems XXIV, 9) makes the

following remark, which has been construed not only as cupellation, but

also as the refining of silver in "tests." "What is the reason that

boiling water does not leap out of the vessel ... silver also does this

when it is purified. Hence those whose office it is in the silversmiths'

shops to purify silver, derive gain by appropriation to themselves of

the sweepings of silver which leap out of the melting-pot."

The quotation of Diodorus Siculus from Agatharchides (2nd century B.C.)

on gold refining with lead and salt in Egypt we give in note 8, p. 279.

The methods quoted by Strabo (63 B.C.-24 A.D.) from Polybius (204-125

B.C.) for treating silver, which appear to involve cupellation, are

given in note 8, p. 281. It is not, however, until the beginning of the

Christian era that we get definite literary information, especially with

regard to litharge, in Dioscorides and Pliny. The former describes many

substances under the terms _scoria_, _molybdaena_, _scoria argyros_ and

_lithargyros_, which are all varieties of litharge. Under the latter

term he says (V, 62): "One kind is produced from a lead sand

(concentrates?), which has been heated in the furnaces until completely

fused; another (is made) out of silver; another from lead. The best is

from Attica, the second (best) from Spain; after that the kinds made in

Puteoli, in Campania, and at Baia in Sicily, for in these places it is

mostly produced by burning lead plates. The best of all is that which is

a bright golden colour, called _chrysitis_, that from Sicily (is called)

_argyritis_, that made from silver is called _lauritis_." Pliny refers

in several passages to litharge (_spuma argenti_) and to what is

evidently cupellation, (XXXIII, 31): "And this the same agency of fire

separates part into lead, which floats on the silver like oil on water"

(XXXIV, 47). "The metal which flows liquid at the first melting is

called _stannum_, the second melting is silver; that which remains in

the furnace is _galena_, which is added to a third part of the ore. This

being again melted, produced lead with a deduction of two-ninths."

Assuming _stannum_ to be silver-lead alloy, and _galena_ to be

_molybdaena_, and therefore litharge, this becomes a fairly clear

statement of cupellation (see note 23, p. 392). He further states

(XXXIII, 35): "There is made in the same mines what is called _spuma

argenti_ (litharge). There are three varieties of it; the best, known as

_chrysitis_; the second best, which is called _argyritis_; and a third

kind, which is called _molybditis_. And generally all these colours are

to be found in the same tubes (see p. 480). The most approved kind is

that of Attica; the next, that which comes from Spain. _Chrysitis_ is

the product from the ore itself; _argyritis_ is made from the silver,

and _molybditis_ is the result of smelting of lead, which is done at

Puteoli, and from this has its name. All three are made as the material

when smelted flows from an upper crucible into a lower one. From this

last it is raised with an iron bar, and is then twirled round in the

flames in order to make it less heavy (made in tubes). Thus, as may be

easily perceived from the name, it is in reality the _spuma_ of a

boiling substance--of the future metal, in fact. It differs from slag in

the same way that the scum of a liquid differs from the lees, the one

being purged from the material while purifying itself, the other an

excretion of the metal when purified."

The works of either Theophilus (1150-1200 A.D.) or Geber (prior to the

14th century) are the first where adequate description of the cupel

itself can be found. The uncertainty of dates renders it difficult to

say which is earliest. Theophilus (Hendrie's Trans., p. 317) says: "How

gold is separated from copper: But if at any time you have broken copper

or silver-gilt vessels, or any other work, you can in this manner

separate the gold. Take the bones of whatever animal you please, which

(bones) you may have found in the street, and burn them, being cold,

grind them finely, and mix with them a third part of beechwood ashes,

and make cups as we have mentioned above in the purification of silver;

you will dry these at the fire or in the sun. Then you carefully scrape

the gold from the copper, and you will fold this scraping in lead beaten

thin, and one of these cups being placed in the embers before the

furnace, and now become warm, you place in this fold of lead with the

scraping, and coals being heaped upon it you will blow it. And when it

has become melted, in the same manner as silver is accustomed to be

purified, sometimes by removing the embers and by adding lead, sometimes

by re-cooking and warily blowing, you burn it until, the copper being

entirely absorbed, the gold may appear pure."

We quote Geber from the Nuremberg edition of 1545, p. 152: "Now we

describe the method of this. Take sifted ashes or _calx_, or the powder

of the burned bones of animals, or all of them mixed, or some of them;

moisten with water, and press it with your hand to make the mixture firm

and solid, and in the middle of this bed make a round solid crucible and

sprinkle a quantity of crushed glass. Then permit it to dry. When it is

dry, place into the crucible that which we have mentioned which you

intend to test. On it kindle a strong fire, and blow upon the surface of

the body that is being tested until it melts, which, when melted, piece

after piece of lead is thrown upon it, and blow over it a strong flame.

When you see it agitated and moved with strong shaking motion it is not

pure. Then wait until all of the lead is exhaled. If it vanishes and

does not cease its motion it is not purified. Then again throw lead and

blow again until the lead separates. If it does not become quiet again,

throw in lead and blow on it until it is quiet and you see it bright and

clear on the surface."

Cupellation is mentioned by most of the alchemists, but as a

metallurgical operation on a large scale the first description is by

Biringuccio in 1540.

[27] In Agricola's text this is "first,"--obviously an error.

[28] The Roman _sextarius_ was about a pint.

[29] This sentence continues, _Ipsa vero media pars praeterea digito_,

to which we are unable to attribute any meaning.

[30] _Thus_, or _tus_--"incense."

[31] One _centumpondium_, Roman, equals about 70.6 lbs. avoirdupois; one

_centner_, old German, equals about 114.2 lbs. avoirdupois. Therefore,

if German weights are meant, the maximum charge would be about 5.7 short

tons; if Roman weights, about 3.5 short tons.

[32] See description, p. 269.