But this latter part is of a different nature. It is a practical

Treatise, intended to contain the manner of performing the principal

Operations of Chymistry; the operations which serve as standards for

regulating all the rest, and which confirm the fundamental truths laid

down in the Theory.

As these operations consist almost wholly of analyses and

decompositions, there can be no doubt concerning the order proper to

be observed in giving an account of them: it evidently coincides with

that of the analysis itself.

But as all bodies, which are the subjects of Chymical operations,

are divided by nature into three classes or kingdoms, the mineral,

the vegetable, and the animal, the analysis thereof may naturally be

divided into three branches: some difference may also arise from the

different order in which these three may be treated of.

As the reasons assigned for beginning with one kingdom rather than with

another have never been thoroughly canvassed, and may perhaps seem

equally good when viewed in a particular light, Chymical writers differ

in their opinions on this point. For my part, without entering into

a discussion of the motives which have determined others to follow a

different order, I shall only produce the reasons that led me to begin

with the mineral kingdom, to examine the vegetable in the second place,

and to conclude with the animal.

First, then, seeing vegetables draw their nourishment from minerals,

and animals derive theirs from vegetables, the bodies which constitute

these three kingdoms seem to be generated the one by the other, in a

manner that determines their natural rank.

Secondly, this disposition procures us the advantage of tracing the

principles, from their source in the mineral kingdom, down to the

last combinations into which they are capable of entering, that is,

into animal matters; and of observing the successive alterations they

undergo in passing out of one kingdom into another.

Thirdly and lastly, I look upon the analysis of minerals to be the

easiest of all; not only because they consist of fewer principles than

vegetables and animals, but also because almost all of them are capable

of enduring the most violent action of fire, when that is necessary to

their decomposition, without any considerable change or diminution of

their principles, to which those of other substances are frequently

liable.

Besides, I am not singular in this distribution of the three classes

of bodies, which are the subjects of the chymical analysis: as it is

the most natural, it has been adopted by several authors, or rather by

most who have published Treatises of Chymistry. But there is something

peculiarly my own in the manner wherein I have treated the analysis of

each kingdom. In the mineral kingdom, for instance, will be found a

considerable number of operations not to be met with in other Treatises

of Chymistry; the authors having probably considered them as useless,

or in some measure foreign, to the purpose of Elementary Books, and

as constituting together a distinct art. I mean the processes for

extracting saline and metallic substances from the minerals containing

them.

Yet, if it be considered that salts, metals, and semi-metals are

far from being produced by nature in a state of perfection, or in

that degree of purity which they are commonly supposed to have when

they are first treated of in Books of Chymistry; but that, on the

contrary, these substances are originally blended with each other, and

adulterated with mixtures of heterogeneous matters, wherewith they form

compound minerals; I imagine it will be allowed, that the operations by

which these minerals are decomposed, in order to extract the metals,

semi-metals, and other simpler substances, especially as they are

founded on the most curious properties of these substances, are so

far from being useless or foreign to the purposes of an Elementary

Treatise, that they are, on the contrary, absolutely necessary thereto.

After I had made these reflections, I could not help thinking that

an analysis of minerals, which should treat of saline and metallic

substances, without taking any notice of the manner in which their

matrices must be analysed, in order to extract them, would be no less

defective than a treatise of the analysis of vegetables, in which Oils,

essential Salts, fixed and volatile Alkalis, should be amply treated

of, without saying one word of the manner of analysing the plants from

which these several substances are obtained. I therefore thought myself

indispensably obliged to describe the manner of decomposing every ore

or mineral, before I attempted to treat of the saline or metallic

substance which it yields.

For example: as the Vitriolic Acid, with the consideration of which I

begin my Mineral Analysis, is originally contained in Vitriol, Sulphur,

and Alum; and as these substances again derive their origin from the

sulphureous and ferruginous Pyrites, the first operations I describe

under this head are the processes for decomposing the Pyrites in order

to extract its Vitriol, Sulphur, and Alum. I then proceed to the

particular analysis of each of these substances, with a view to extract

their Vitriolic Acid; and afterwards deliver, in their order, the other

operations usually performed on this Acid. Thus it appears, that this

saline substance occasions my describing the analyses of the Pyrites,

Vitriol, Sulphur, and Alum. The whole of the Treatise on Minerals

proceeds on the same plan.

The operations by which we decompose ores and minerals are of two

sorts: those employed in working by the great, and those for trying

in small the yield of any ore. These two manners of operating are

sometimes a little different; yet in the main they are the same,

because they are founded on the same principles, and produce the same

effects.

As my chief design was to describe the operations that may be

conveniently performed in a laboratory, I have preferred the processes

for small assays: especially as they are usually performed with more

care and accuracy than the operations in great works: and here I must

acknowledge, that I am obliged to M. Cramer's _Docimasia_, or Art

of Assaying, for all the operations of this kind in my analysis of

minerals. As M. Hellot's work on that subject did not appear till after

I had finished this, M. Cramer's _Docimasia_, in which sound Theory is

joined with accurate practice, was the best book of the kind I could

at that time consult. I therefore preferred it to all others; and as I

have not quoted it in my analysis of minerals, because the quotations

would have been too frequent, let what I say here serve for a general

quotation. I have been careful to name, as often as occasion required,

the other authors whose processes I have borrowed: it is a tribute

justly due to those who have communicated their discoveries to the

public.

Though I have told the reader that in my analysis of minerals he will

find the processes for extracting out of each the saline or metallic

substances contained in it, yet he must not expect that this book

will instruct him in all that is necessary he should know to be able

to determine, by an accurate assay, the contents of every mineral.

My intention was not to compose a Treatise of Assaying; and I have

taken in no more than was absolutely necessary to make the analysis

of minerals perfectly understood, and to render it as complete as it

ought to be in an Elementary Treatise. I have therefore described only

the principal operations relating thereto; the operations which are

fundamental, and which, as I said before, are to serve as standards

for the rest, abstracted from such additional circumstances as are of

consequence only to the Art of Assaying, properly so called.

Such therefore as are desirous of being fully instructed in that Art,

must have recourse to those works which treat professedly of the

subject; and particularly to that published by M. Hellot: a performance

most esteemed by such as are best skilled in Chymistry, and rendered

so complete by the numerous and valuable observations and discoveries

of the Author, that nothing better of the kind can be wished for. I

thought it proper to give these notices in relation to my analysis of

minerals; and shall now proceed to shew the plan of my analyses of

vegetables and of animals.

Seeing all vegetable matters are susceptible of fermentation, and when

analysed after fermentation, yield principles different from those we

obtain from them before they are fermented, I have divided them into

two classes; the former including vegetables in their natural state,

before they have undergone fermentation; and the latter those only

which have been fermented. This analysis opens with the processes

by which we extract from vegetables all the principles they will

yield without the help of fire: and then follow the operations for

decomposing plants by degrees of heat, from the gentlest to the most

violent, both in close vessels, and in the open air.

I have not made the same division in the animal kingdom, because the

substances that compose it are susceptible only of the last degree of

fermentation, or putrefaction; and moreover the principles they yield,

whether putrefied or unputrefied, are the very same, and differ only

with regard to their proportions, and the order in which they are

extricated during the analysis.

I begin this analysis with an examination of the milk of animals that

feed wholly on vegetables; because, though this substance be elaborated

in the body of the animal, and by that means brought nearer to the

nature of animal matters, yet it still retains a great similitude

to the vegetables from which it derives its origin, and is a sort

of intermediate substance between the vegetable and animal. Then I

proceed to the analysis of animal matters properly so called, those

which actually make a part of the animal body. I next examine the

excrementitious substances, that are thrown out of the animal body as

superfluous and useless. And then I conclude this latter part with

operations on the Volatile Alkali; a saline substance of principal

consideration in the decomposition of animal matters.

Though, in the general view here given of the order observed in this

Treatise of Practical Chymistry, I have mentioned only such processes

as serve for analysing bodies, yet I have also inserted some other

operations of different kinds. The book would be very defective if

it contained no more: for the design of Chymistry is not only to

analyse the mixts produced by nature, in order to obtain the simplest

substances of which they are composed, but moreover to discover by

sundry experiments the properties of those elementary principles, and

to recombine them in various manners, either with each other, or with

different bodies, so as to reproduce the original mixts with all their

properties, or even form new compounds which never existed in nature.

In this book therefore the reader will find processes for combining

and recompounding, as well as for resolving and decomposing bodies. I

have placed them next to the processes for decomposition, taking all

possible care not to interrupt their order, or break the connection

between them.

PART I.

OF MINERALS.

SECTION I.

_Operations performed on Saline Mineral Substances._

CHAP. I.

_Of the_ VITRIOLIC ACID.

PROCESS I.

_To extract Vitriol from the Pyrites._

Take any quantity you please of Iron Pyrites; leave them for some time

exposed to the air: they will crack, split, lose their brightness, and

fall into powder. Put this powder into a glass cucurbit, and pour upon

it twice its weight of hot water; stir the whole with a stick, and the

liquor will grow turbid. Pour it, while it is yet warm, into a glass

funnel lined with brown filtering paper; and having placed your funnel

over another glass cucurbit, let the liquor drain into it. Pour more

hot water on the powdered Pyrites, filter as before, and so go on,

every time lessening the quantity of water, till that which comes off

the Pyrites appears to have no astringent vitriolic taste.

Put all these waters together into a glass vessel that widens upwards;

set it on a sand-bath, and heat the liquor till a considerable smoke

arises; but take care not to make it boil. Continue the same degree of

fire till the surface of the liquor begins to look dim, as if some

dust had fallen into it; then cease evaporating, and remove the vessel

into a cool place: in the space of four and twenty hours will be formed

therein a quantity of crystals, of a green colour and a rhomboidal

figure: these are Vitriol of Mars, or Copperas. Decant the remaining

liquor; add thereto twice its weight of water; filter, evaporate, and

crystallize as before; repeat these operations till the liquor will

yield no more crystals, and keep by themselves the crystals obtained at

each crystallization.

_OBSERVATIONS._

The Pyrites are minerals which, by their weight and shining colours,

frequently impose on such as are not well acquainted with ores. At

first sight they may be taken for very rich ones; and yet they consist

only of a small quantity of metal combined with much sulphur or

arsenic, and sometimes with both.

They strike fire with a steel as flints do, and emit a sulphureous

smell: so that they may be known by this extemporaneous proof. The

metal most commonly and most abundantly found in the Pyrites is iron;

the quantity whereof sometimes equals, or even exceeds, that of the

sulphur. Besides metallic and sulphureous matters, the Pyrites contain

also some unmetallic earth.

There are several sorts of Pyrites: some of them contain only iron and

arsenic. They have not all the property of efflorescing spontaneously

in the air, and turning into vitriol: none do so but such as consist

only of iron and sulphur, or at least contain but a very small portion

of copper, or of arsenic: and even amongst those that are composed of

iron and sulphur alone, there are some that will continue for years

together exposed to the air without shooting, and indeed without

suffering the least sensible alteration.

The efflorescence of the Iron Pyrites, and the changes they undergo,

are phenomena well worth our notice. They depend on the singular

property which iron possesses of decomposing sulphur by the help of

moisture. If very fine iron-filings be accurately mingled with flowers

of sulphur, this mixture, being moistened with water, grows very hot,

swells up, emits sulphureous vapours, and even takes fire; what remains

is found converted into Vitriol of Mars. On this occasion, therefore,

the sulphur is decomposed; its inflammable part is dissipated or

consumed; its acid combines with the iron, and a Vitriol arises from

that conjunction.

This is the very case with the Pyrites that consist only of iron

and sulphur; yet some of them, as we said before, do not effloresce

spontaneously and turn to Vitriol. The reason probably is, that, in

such minerals, the particles of iron and sulphur are not intimately

mixed together, but separated by some earthy particles.

In order to procure Vitriol from Pyrites of this kind, they must be

for some time exposed to the action of fire, which, by consuming part

of their sulphur, and rendering their texture less compact, makes way

for the air and moisture, to which they must be afterwards exposed, to

penetrate their substance, and produce in them the changes with which

those others are affected that germinate spontaneously.

The Pyrites which contain copper and arsenic, and for that reason

do not effloresce, must likewise undergo the action of fire; which,

besides the effects it produces on Pyrites that consist of iron and

sulphur only, dissipates also the greatest part of the arsenic. These

Pyrites being first roasted, and then exposed to the air for a year or

two, do also yield Vitriol; but then it is not a pure Vitriol of Iron,

but is combined with a portion of blue Vitriol, the basis of which is

Copper.

Sometimes also there is Alum in the vitriolic waters drawn off the

Pyrites. It was on account of this mixture of different salts that we

recommended the keeping apart the crystals obtained from each different

crystallization: for by this means they may be examined separately, and

the species to which they belong discovered.

When Vitriol of Iron is adulterated with a mixture of the Vitriol

of Copper only, it is easy to purify it and bring it to be entirely

martial, by dissolving it in water, and setting plates of iron in the

solution: for iron having a greater affinity than copper with the

vitriolic acid, separates the latter from it, and assuming its place

produces a pure Vitriol of Mars.

In large works for extracting Vitriol from the Pyrites they proceed

thus. They collect a great quantity of Pyrites on a piece of ground

exposed to the air, and pile them up in heaps of about three feet high.

There they leave them exposed to the action of the air, sun, and rain,

for three years together; taking care to turn them every six months,

in order to facilitate the efflorescence of those which at first lay

undermost. The rain-water which has washed those Pyrites is conveyed by

proper channels into a cistern; and when a sufficient quantity thereof

is gathered, they evaporate it to a pellicle in large leaden boilers,

having first put into it a quantity of iron, some part of which is

dissolved by the liquor, because it contains a vitriolic acid that is

not fully saturated therewith. When it is sufficiently evaporated, they

draw it off into large leaden or wooden coolers, and there leave it to

shoot into crystals. In these last vessels several sticks are placed,

crossing each other in all manner of directions, in order to multiply

the surfaces on which the crystals may fasten.

The Pyrites are not the only minerals from which Vitriol may be

procured. All the ores of iron and copper that contain sulphur may

also be made to yield green or blue Vitriol, according to the nature

of each, by torrefying them, and leaving them long exposed to the air:

but this use is seldom made of them, as there is more profit to be got

by extracting the metals they contain. Besides, it is easier to obtain

Vitriol from the Pyrites than from those other mineral substances.

PROCESS II.

_To extract Sulphur from the Pyrites, and other sulphureous Minerals._

Reduce to a coarse powder any quantity of yellow Pyrites, or other

Mineral containing Sulphur. Put this powder into an earthen or glass

retort, having a long wide neck, and so large a body that the matter

may fill but two thirds of it. Set the retort in a sand-bath fixed over

a reverberating furnace: fit to it a receiver half full of water, and

so placed that the nose of the retort may be about an inch under the

water: give a gradual fire, taking care you do not make it so strong as

to melt the matter. Keep the retort moderately red for one hour, or an

hour and half, and then let the vessels cool.

Almost all the Sulphur separated by this operation from its matrix

will be found at the extremity of the neck of the retort, being fixed

there by the water. You may get it out either by melting it with such a

gentle heat as will not set it on fire, or by breaking the neck of the

retort.

_OBSERVATIONS._

Of all minerals the Pyrites contain the most Sulphur; those especially

which have the colour of fine brass, a regular form, such as round,

cubical, hexagonal, and being broken present a number of shining

needles, all radiating, as it were, from a center.

A very moderate heat is sufficient to separate the Sulphur they

contain. We directed that the retort employed should have a long and

wide neck, with a view to procure a free passage for the Sulphur: the

water set in the receiver detains the Sulphur, fixes it, and prevents

it from flying off; so that it is unnecessary to close the joints of

the vessels. But it is proper to take notice, that whenever you use

an apparatus for distilling, which requires the beak of the retort

to be under water, it is of very great consequence that the fire be

constantly so regulated, that the retort may not cool in the least;

for, in that case, as the rarefied air contained therein would be

condensed, the water in the receiver would rise into the retort and

break it.

If in distilling Sulphur, according to the present process, the matter

contained in the retort should happen to melt, the operation would be

thereby considerably protracted, and it would require a great deal

more time to extract all the Sulphur; because all evaporation is from

the surface only, and the matter, while it remains in a coarse powder,

presents a much more extensive surface than when it is melted.

This remark holds with regard to all other distillations. Any quantity

of liquor, set to distil in its fluid state, will take much more time

to rise in vapours, and pass from the retort into the receiver, than

if it be incorporated with some solid body reduced to minute parts, so

that the whole shall make a moist powder; and this though the very same

degree of fire be applied in both cases.

If the matter from which it is proposed to extract Sulphur be such as

will melt with the degree of fire necessary to this operation; that

is, with a heat which will make the retort but faintly red, it must

be mixed with some substance that is not so fusible. Very pure coarse

sand, or clean gravel, may be used with success: but absorbent earths

are altogether improper for this purpose, because they will unite with

the Sulphur.

The sulphureous minerals which are most apt to fuse are the cupreous

Pyrites, or yellow copper ores: common lead ores are also very fusible.

The Pyrites are by this operation deprived of almost all the Sulphur

they contain; and consequently little is left behind, but the particles

of iron and copper, together with a portion of unmetallic earth, which

we shall shew how to separate from these metals, when we come to

treat of them. I say that by this operation the Pyrites are deprived

of almost all, and not entirely of all their Sulphur; because, this

separation being made in close vessels only, there always remains

a certain quantity of Sulphur, which adheres so obstinately to the

metals, that it would be almost impossible to get it all out, even

though a much stronger fire than that directed in the process were

applied for this purpose, and though choice had been, as it ought to

be, made of such Pyrites, or other sulphureous Minerals as part most

easily with their sulphur. Nothing but a very strong fire in the open

air is capable of carrying it wholly off, or consuming it entirely.

In several places are found great quantities of native Sulphur. The

Volcanoes abound with it, and people gather it at the foot of those

burning mountains. Several springs of mineral waters also yield

Sulphur, and it is sometimes found sublimed to the vaulted roofs of

certain wells, and among others in one at Aix-la-Chapelle.

The Germans and Italians have large works for extracting Sulphur in

quantities out of Pyrites, and other minerals which abound therewith.

The process they work by is the same with that here delivered; but with

this difference only, that Sulphur being but of small value they do

not use so many precautions. They content themselves with putting the

sulphureous minerals into large crucibles, or rather earthen cucurbits,

which they place in the furnace in such a manner that, when the

sulphureous part melts, it runs into vessels filled with water, and is

thereby fixed.

The Sulphur obtained, either by distillation or by simple fusion, is

not always pure.

When it is obtained by distillation, if the matters from which you

extract it contain moreover some other minerals of nearly the same

volatility, such, for instance, as Arsenic, or Mercury, these minerals

will come over with it. This is easily perceived: for pure sublimed

Sulphur is always of a beautiful yellow, inclining to a lemon colour.

If it look red, or have a reddish cast, it is a sign that some Arsenic

hath risen along with it.

Mercury sublimed with Sulphur likewise gives it a red colour; but

Sulphur is very seldom adulterated with this metallic substance: for

Arsenic is frequently found combined with the Pyrites, and other

sulphureous minerals; whereas, on the contrary, we very rarely meet

with any Mercury in them.

But if Mercury should happen to rise with the Sulphur in distillation,

it may be discovered by examining the sublimate; which, in that case,

will have the properties of Cinabar: on being broken its inside will

appear to consist of needles adhering laterally to each other; its

weight will be very considerable; and, lastly, the great heat of the

place where it is collected will furnish another mark to know it by;

for, as Cinabar is less volatile than Arsenic or Sulphur, it fastens on

places too hot for either Sulphur or Arsenic to bear.

Sulphur may also be adulterated with such fixed matters, either

metallic or earthy, as it may have carried up along with it in the

distillation, or as may have been sublimed by the Arsenic, which has a

still greater power than Sulphur to volatilize fixed bodies.

If you desire to free the Sulphur from most of these heterogeneous

matters, it must be put into an earthen cucurbit, and set in a

sand-bath. To the cucurbit must be fitted one or more aludels, and such

a degree of heat applied as shall but just melt the Sulphur; which is

much less than that necessary to separate the Sulphur from its matrix.

As soon as the Sulphur is melted it will sublime in lemon-coloured

flowers, that will stick to the insides of the aludels.

When nothing more appears to rise with this degree of heat, the vessels

must be suffered to cool. At the bottom of the cucurbit will be found

a sulphureous mass, containing the greatest part of the adventitious

matters that were mixed with the Sulphur, and more or less red or

dark-coloured, according to the nature of those matters.

When we come to treat of Arsenic and Mercury, we shall give the methods

of separating Sulphur entirely from those metallic substances.

PROCESS III.

_To extract Alum from aluminous Minerals._

Take such minerals as are known or suspected to contain Alum. Expose

them to the air, that they may effloresce. If they remain there a year

without any sensible change, calcine them, and then leave them exposed

to the air, till a bit thereof being put on the tongue imparts an

astringent aluminous taste.

When your matters are thus prepared, put them into a leaden or glass

vessel; pour upon them thrice their weight of hot water; boil the

liquor; filter it; and repeat these operations till the earth be so

edulcorated that the water which comes off it hath no taste. Mix all

these solutions together, and let them stand four and twenty hours,

that the gross and earthy parts may settle to the bottom; or else

filter the liquor: then evaporate till it will bear a new-laid egg. Now

let it cool, and stand quiet four and twenty hours: in that time some

crystals will shoot, which are most commonly vitriolic; for Alum is

rarely obtained by the first crystallization. Remove these vitriolic

crystals: if any crystals of Alum be found amongst them, these must be

dissolved anew, and set to crystallize a second time in order to their

purification; because they partake of the nature as well as of the

colour of vitriol. By this method extract all the Alum that the liquor

will yield.

If you get no crystals of Alum by this means, boil your liquor again,

and add to it a twentieth part of its weight of a strong alkaline

lixivium, or a third part of its weight of putrefied urine, or a small

quantity of quick-lime. Experience and repeated trials must teach you

which of these three substances is to be preferred, according to the

particular nature of the mineral on which you are to operate. Keep

your liquor boiling, and if there be any alum in it, there will appear

a white precipitate: in that case let it cool and settle. When the

white precipitate is entirely fallen, decant the clear, and leave the

crystals of Alum to shoot at leisure, till the liquor will yield no

more: it will then be exceeding thick.

_OBSERVATIONS._

Alum is obtained from several sorts of Minerals. In some parts of

Italy, and in sundry other places, it effloresces naturally on the

surface of the earth. There it is swept together with brooms, and

thrown into pits full of water. This water is impregnated therewith

till it can dissolve no more. Then it is filtered, and set to evaporate

in large leaden vessels; and when it is sufficiently evaporated, and

ready to shoot into crystals, it is drawn off into wooden coolers, and

there left for the salt to crystallize.

In aluminous soils there are often found springs strongly impregnated

with Alum: so that to obtain it, the water need only be evaporated.

In the country about Rome there is a very hard stone, which is hewn out

of the quarry just like other stones for building; this stone yields

a great deal of Alum. In order to extract it, the stones are calcined

for twelve or fourteen hours; after which they are exposed to the air

in heaps, and carefully watered three or four times a-day for forty

days together. In that time they begin to effloresce, and to throw out

a reddish matter on their surface. Then they are boiled in water, which

dissolves all the Alum they contain, and, being duly evaporated, gives

it back in crystals. This is the Alum called _Roman Alum_.

Several sorts of Pyrites also yield a great deal of Alum. The English

have a stone of this kind, which, in colour, is very like a slate. This

stone contains much Sulphur, which they get rid of by roasting it.

After this they steep the calcined stone in water, which dissolves the

Alum it contains, and to this solution they add a certain quantity of a

lye made of the ashes of sea-weeds.

The Swedes have a Pyrites of a bright golden colour, variegated with

silver spots, from which they procure Sulphur, Vitriol, and Alum. They

separate from it the Sulphur and the Vitriol by the methods above

prescribed. When the liquor which hath yielded Vitriol is become thick,

and no more vitriolic crystals shoot in it, they add an eighth part of

its weight of putrefied urine, mixed with a lye made of the ashes of

green wood. Upon this there appears and falls to the bottom a copious

red sediment. They decant the liquor from this precipitate, and, when

it is duly evaporated, find it shoot into beautiful crystals of Alum.

What hath been said, concerning the several matrices from which Alum

is obtained, sufficiently shews, that it is seldom solitary in the

waters with which aluminous subjects have been lixiviated. It is almost

always accompanied with a certain quantity of Vitriol, or other saline

mineral matters, which obstruct its crystallization, and prevent its

being pure. It is with a view to free it from these matters, that the

waters impregnated with Alum are mixed with a certain quantity of the

lye of some fixed Alkali, or with putrefied urine, which contains much

volatile Alkali. These Alkalis have the property of decompounding

all the Neutral salts which have for their basis either an absorbent

earth or a metallic substance; and such as have a metallic substance

for their basis more readily than those whose basis is an earth.

Consequently, if they are mixed with a liquor in which both these sorts

of salts are dissolved, they must decompound that sort whose basis is

metallic sooner than the other whose basis is an earth. This is what

comes to pass in a solution of Alum and Vitriol. The metallic part of

the latter is separated from its acid by the Alkalis when mixed with

that solution; and it is this metallic part, which is generally iron,

that appears in the form of a reddish precipitate, as above-mentioned.

But because Alkalis decompound also those Neutral salts which have an

earth for their basis, care must be taken that too much thereof be not

added; else what you put in, more than is necessary to decompound the

vitriolic salts in your liquor, will attack the Alum, and decompound it

likewise.

The Alkali made use of to promote the crystallization of the Alum

joins with the Vitriolic Acid, which had dissolved the substances now

precipitated, and therewith forms different Neutral salts according

to its particular nature. If the Alkali be a lixivium of common

wood-ashes, the Neutral salt will be a vitriolated Tartar; if a

lixivium of the ashes of a maritime plant like Soda, the Neutral salt

will be a Glauber's salt; if putrefied urine, the Neutral salt will be

a vitriolic Ammoniacal salt. Some of these salts incorporate with the

Alum, which in large works crystallizes in vast lumps: and hence it

comes that some sorts of Alum when mixed with a fixed Alkali smell like

a volatile Alkali.

The crystals of Alum are octaedral, that is, they are solids with eight

sides. These octaedral solids are triangular pyramids, having their

angles cut away, so that four of their surfaces are hexagons, and the

other four triangles.

Sulphur, Vitriol, and Alum are the three principal subjects in which

we certainly know that the universal or Vitriolic Acid particularly

resides, and from which we extract it when we want to have it pure. For

this reason we thought it proper, before we treated of the extraction

of this Acid, to shew the method of separating those matters themselves

from the other minerals out of which we obtain them.

Moreover, all the other matrices, in which the Vitriolic Acid is most

commonly lodged, may be referred to one or other of the matters which

serve as bases to these three minerals.

To Sulphur we may refer all combinations of the Vitriolic Acid with an

inflammable matter: but we must take care not to confound Sulphur with

those Bitumens in which the Vitriolic Acid may be found: for the basis

of those bitumens is a real Oil; whereas the basis of Sulphur is the

pure Phlogiston. Yet as Oils themselves contain the Phlogiston, which,

in union with the Vitriolic Acid forms a true Sulphur, it follows that

such bitumens may in a certain respect be classed with Sulphur.

The same is to be said of Vitriol. The name is usually given to such

combinations only as are formed of the Vitriolic Acid with Iron or

Copper, which make the green and blue Vitriol; and to a third species

of Vitriol, which is white, and has Zinc for its basis: but as the

Vitriolic Acid may, by particular combinations, be united with many

other metallic substances, all such Metallic Salts must be referred to

the class of Vitriols.

The same may also be said of Alum, which is no other than a combination

of the Vitriolic Acid with a particular kind of absorbent earth; so

that all combinations of this Acid with any earth whatever may be

placed in the same class.

This last class of mixts is the most extensive of all that contain the

Vitriolic Acid; because there are a vast many earths, all differing

from one another, with which that Acid may be united. Alum properly

so called, the Gypsums, Talcs, Selenites, Boles, and all the other

compounds of this kind, differ from each other only in their particular

earths.

The different properties of these earthy salts depend on the nature of

their bases. Those which are of the aluminous kind retain much water in

crystallizing, which makes them very soluble in water, and gives them

the property of acquiring readily the aqueous fluor when exposed to the

fire. Those which are of the nature of the Selenites admit but very

little water in their crystals, and consequently are almost insoluble

in water; nor does the fire give them an aqueous fluor. Lastly, the

Gypsums and Talcs are still more destitute of these properties. The

natures of the earths in these several compounds are hitherto but very

imperfectly known, and may give the Chymists occasion for inquiries

equally curious and useful.

The Vitriolic Acid is sometimes found complicated with a fixed alkaline

basis. This is almost always the Alkali of Sea-salt; so that the

compound is a Glauber's Salt. Some mineral waters are impregnated

therewith; which happens when these waters contain Vitriol or Alum,

together with Sea-salt.

From the principles laid down, in our Elements of the Theory, it

appears that the Vitriolic Acid hath not so great an affinity with

earthy and metallic substances as with fixed Alkalis; and also that it

is stronger than the Marine Acid, and hath a greater affinity with

fixed Alkalis. This being allowed, the generation of native Glauber's

Salts is easily accounted for. The Acid of aluminous or vitriolic Salts

quits the earth or the metal with which it was combined, and expelling

the Acid of Sea-salt unites with its basis. Warmth greatly promotes

these decompositions.

If the common fossil salt, usually called _Sal Gem_, or any other kind

of Sea-salt, should happen to be near a Volcano, when it discharges

flaming Sulphur, as is frequently the case, and if this Sulphur should

run among the Sea-salt, a Glauber's Salt would instantly be formed in

that place; because when Sulphur burns, its Acid is separated and set

at liberty.

Lastly, if aluminous or vitriolic matters, or burning Sulphur, should

meet with the ashes of plants or trees consumed by fire, a vitriolated

Tartar would be formed, because these ashes contain a fixed Alkali of

the same nature with that of Tartar.

The Vitriolic Acid when combined with an earthy basis adheres strongly

thereto; so that the force of fire is able to expel very little or

none of it. There is no way of separating it from such a basis, but by

presenting to it an Alkaline Salt, with which it will unite: nor is it

ever extracted from such matters when it is required pure. It does not

adhere so firmly to metallic substances; but is separated from them by

the force of fire: so that it may be obtained from the several sorts

of Vitriol. It is usually drawn from Green Vitriol; that being the

commonest sort.

As to Sulphur, the Phlogiston which is its basis being the substance

wherewith the Vitriolic Acid hath the greatest affinity, it would be

altogether impossible to decompose it, and to separate its Acid, if it

were not inflammable; but by burning it the Phlogiston is destroyed,

and leaves the Acid at liberty. By this means therefore it may be

separated. We shall now give the processes for extracting the Acid from

Vitriol and Sulphur.

PROCESS IV.

_To extract the Vitriolic Acid from Green Vitriol._

Take any quantity of Green Vitriol: put it in an unglazed earthen

vessel, and heat it gradually. Vapours will soon begin to rise.

Increase the fire a little, and it will liquefy by means of the

water contained in it, and acquire what we called an _aqueous_ fluor.

Continue the calcination, and it will become less and less fluid, grow

thick, and turn of a greyish colour. Now raise your fire, and keep it

up till the salt recover its solidity, acquire an orange colour, and

begin to grow red where it immediately touches the sides of the vessel.

Then take it out, and reduce it to powder.

Put the Vitriol thus calcined and pulverized into a good earthen

retort, of which one half at least must remain empty. Set the retort

in a reverberatory furnace: fit thereto a large glass receiver, and,

having luted the joint well, give fire by degrees. You will soon see

white clouds rise into the receiver, which will render it opaque, and

heat it. Continue the same degree of fire till these clouds disappear:

they will be succeeded by a liquor which will trickle down the sides

of the receiver in veins. Still keep up the fire to the same degree

as long as these veins appear. When they begin to abate, increase the

fire, and push it to the utmost extremity: upon this, there will come

over a black, thick liquor: it will even be found congealed, and prove

the icy Oil of Vitriol, if care hath been taken to change the receiver,

keep the vessels perfectly close, and give a sufficient degree of heat.

Proceed thus till nothing more comes over, or at least very little. Let

the vessels cool, unlute them, pour the contents of the receiver into a

bottle, and seal it hermetically.

_OBSERVATIONS._

Green Vitriol retains much water in crystallizing; and, in order to

free it from that superfluous phlegm, it must be calcined before you

distil it. Without this precaution the operation will be exceedingly

protracted, and a great deal of time wasted in distilling such a

quantity of water; which will moreover greatly weaken the Acid by

commixing with it, unless care be taken to change the recipient as soon

as the water is all come over.

But there is also another advantage in calcining the Vitriol before

you put it into the retort: for otherwise this salt would melt on the

first application of heat, and run into a mass; which would prove a

great hindrance to its distillation. This inconvenience is avoided by

a previous calcination, in consequence whereof the Vitriol is easily

reduced to a powder which never becomes fluid.

Vitriol calcined as directed in the process grows so hard, and adheres

so firmly to the vessel in which the calcination is performed, that

it requires no small pains to separate and pulverize it. Care must

be taken to put it into the retort as soon as it is pulverized, and

to stop that vessel very close if you do not begin the distillation

immediately: for otherwise it will naturally attract from the air

almost all the moisture it hath lost.

The Acid which Vitriol yields by distillation is sulphureous; probably

because it still retains some of the Phlogiston, with which it was

united when under the form of sulphur in the Pyrites; or else hath laid

hold on a portion of that belonging to the iron which served for its

basis in Vitriol. But this sulphureous part is volatile, and flies off

in time.

This decomposition of Vitriol in close vessels is a difficult and

laborious process. To carry the operation to its utmost perfection

requires a fire of extreme violence, kept up without intermission

during four or five days; such in short as few vessels are able to

bear. Of course this operation is seldom performed in laboratories.

The French Chymists fetch their Oil of Vitriol from Holland, where it

is extracted from Vitriol in large quantities, by means of furnaces

erected for the purpose, in which many retorts are employed at once.

In the Memoirs of the Academy of Sciences M. Hellot hath given us the

most material circumstances of a very fine experiment of this kind, in

which he pushed the distillation of Green Vitriol to the utmost. Into

a German retort[5] he put six pounds of Green English Vitriol calcined

to redness, which he exposed to a fire of the extremest violence,

constantly kept up during four days and four nights. At the expiration

of that time he found in the vessels employed as receivers an Icy Oil

of Vitriol, which was altogether in a crystalline form and black. The

precautions necessary to make this experiment succeed, he represents,

in the following terms.

[5] They are much the best, and bear a very fierce heat.

"The success of this operation, which produces an Oil of Vitriol

perfectly Icy and without any liquor, depends on the care taken to

prevent the acid vapours, driven by the fire out of Vitriol calcined to

redness, from having any communication with the external air while they

are distilling: for otherwise they will attract from it a moisture

which will keep them fluid in the receiver. The receiver must be at

such a distance from the furnace that it may remain cool enough for

the vapours to condense in it. There must also be sufficient room

for those vapours to circulate in, and to prevent the sulphureous

explosions, which are every now and then discharged out of the retort,

from bursting the vessels: for though the previous calcination of the

Vitriol hath carried off the most volatile, yet there still remains

enough of the inflammable principle, even in the iron itself, to

form a Sulphur with the Acid as it is extricated, or at least a mixt

that would be as apt to take fire as common Sulphur, if it were not

over-dosed with the Acid.

"As the best means of gaining these ends, M. Hellot contrived to adapt

to the neck of his retort a receiver with two necks, the lowermost of

which was inserted into a large ballon. Receivers applied to each other

in this manner are called Adopters.

"It is no easy matter to get this Icy Oil out of the ballon: for as

soon as the air touches it such a thick cloud of sulphureous fumes

arises, that it is absolutely necessary to place the vessel on some

shelf over head, because a man cannot stand exposed thereto for a

single minute without being suffocated."

This Icy Acid must be shut up with all possible expedition in a

crystal bottle accurately closed with a glass stopple, which should be

ground with emery in its neck so as to fit it exactly: for it attracts

moisture so powerfully, that, unless exceeding great care be taken to

prevent all communication with the external air, it will soon dissolve

into a fluid.

"The Icy Oil is black; because the acid vapours carry over with them

something of a greasy matter, from which Vitriol is seldom free, and

which always appears, after repeated solutions and crystallizations

of this Salt, in the mother-water which will shoot no more. Now the

smallest portion of inflammable matter presently blackens the most

highly rectified Oil of Vitriol, which is perfectly clear.

"The Vitriolic Acid, when forced over by a violent heat, carries

along with it some ferruginous particles also, that want nothing but

to be united with a phlogiston to become true iron. They are easily

discovered, either in the common black Oil of Vitriol, or in the

blackish crystals of the Icy Oil, by only dissolving them in a large

quantity of distilled water: for after seven or eight days digestion

a light powder or downy sediment precipitates, which being calcined

in a violent fire is partly attracted by the magnet; and being again

calcined with bees-wax becomes almost entirely iron."

The _Caput mortuum_ of this distillation of Vitriol is the ferruginous

earth of this Salt, and is called _Colcothar_. When this Colcothar hath

undergone a violent fire, as in the experiment now related, scarce any

Acid remains therein. Out of six pounds of Vitriol that M. Hellot used,

he could recover no more, by lixiviating what was left in the retort,

than two ounces of a Vitriolic Salt; and even that was very earthy.

If Vitriol be exposed to a fire neither so violent nor so long

continued, its Colcothar will yield a greater quantity of Vitriol that

hath not been decomposed. A white crystalline salt is also obtained

from it, and called _Salt of Colcothar_; which is no other than the

small portion of Alum usually contained in Vitriol, and not so easily

decomposed by the the action of fire.

PROCESS V.

_To decompose Sulphur, and extract its Acid, by burning it._

Take any quantity of the purest Sulphur: fill therewith a crucible or

other earthen dish: heat it till it melts; then set it on fire, and,

when its whole surface is lighted, place it under a large glass head,

taking care that the flame of the Sulphur do not touch either its sides

or bottom; that the air have free access, in order to make the Sulphur

burn clear; and that the head incline a little toward the side on which

its beak is, that, as the vapours condense therein, the liquor may run

off with ease. To the beak of this vessel fit a receiver: the fumes of

the lighted sulphur will be condensed, and gather into drops in the

head, out of which they will run into the receiver. There, when the

Sulphur has done burning, you will find an Acid liquor, which is the

Spirit of Sulphur.

_OBSERVATIONS._

In the burning of Sulphur, the Phlogiston which serves for its basis

is dissipated, and separated from the acid which is left at liberty.

The acid fumes which rise from the lighted sulphur strike against the

inside of the head placed over it, are there condensed, and appear

in the form of a liquor. But as Sulphur, like all other inflammable

bodies, Nitre excepted, will not burn in close vessels, it is necessary

that the air be freely admitted here; which occasions the loss of a

great deal of the Acid of the Sulphur, as is evident from the pungent

suffocating smell perceived in the laboratory during the operation.

This Acid, while combined with the Phlogiston, is incapable of

contracting any union with water; but when alone is very apt to mix

therewith: it is even proper to put some in its way, that it may

incorporate therewith as soon as it is discharged from the Sulphur; for

it is then very free from phlegm, very volatile, and consequently very

little disposed to condense into a liquor, but, on the contrary, very

apt to fly off in vapours. The water, which it imbibes with a kind of

avidity, fixes and detains it; so that by this means a much greater

quantity thereof is obtained from Sulphur, than if it were distilled

without this precaution.

It is proper, therefore, now and then, to introduce a dish full of

hot water under the head which receives the fumes of the Sulphur. The

vapours that exhale from the water be-dew the inside of the head, and

procure the advantage we are speaking of.

The same thing may be effected several other ways: thus, the crucible

containing the Sulphur may be set on a foot placed in an earthen dish

with some water in it; which, however, must not rise above the foot;

for if it should reach the crucible, it might cool and fix the sulphur.

The dish thus prepared must be placed on a sand-bath hot enough to make

the water smoke continually; and over all is to be placed the head as

directed in the process.

The size and form of the vessel which immediately receives the

sulphureous fumes may also contribute to increase the quantity of the

Acid Spirit. A very large vessel, with a hole at bottom no wider than

is just sufficient to admit the vapours, is the properest for this

operation.

After the Sulphur has burnt for some time, it often happens that a sort

of skin or crust forms on its surface, which is not inflammable, but

gradually lessens the quantity and vigour of the flame as it increases

in thickness, and at last puts it quite out. This crust proceeds from

the impurities, and heterogeneous uninflammable particles contained in

the sulphur. Care must be taken to remove it with an iron wire as fast

as it forms.

Two quantities of sulphur may also be kept in two crucibles, and

heated alternately. That in which the Sulphur is hot and melted may be

substituted for the other in which the Sulphur is grown cold and fixed;

because cold Sulphur does not burn well.

The Spirit of Sulphur is at first pungent and volatile, because it

still retains a small portion of the Phlogiston: but that sulphureous

part flies off, especially if the bottle in which the Spirit is kept be

left for some time unstopped.

The Acid obtained from Sulphur appears by all chymical proofs perfectly

like that obtained from Vitriol: they differ in this only, that the

former is the purest; for the Acid obtained from Vitriol carries over

with it some metallic parts, as we observed before, which can never

happen to that obtained from Sulphur.

If linen rags dipped in a solution of Fixed Alkali be exposed to the

fumes of burning brimstone, the Spirit of Sulphur joins with the

Alkali, and therewith forms a Vitriolated Tartar. This Salt is known

to be formed when the rags grow stiff, and appear spangled with a vast

many glittering points, which are nothing but little crystals of the

Salt we are speaking of.

When the Sulphur burns very gently and slowly the Spirit that exhales

from it is so much the more sulphureous and volatile: and hence the

Salt formed by the combination of this Spirit with the Alkali exposed

to it in linen rags, as in the above-mentioned experiment, is not

at first a Vitriolated Tartar; but a Neutral Salt of a particular

kind, which is capable of being decomposed by any other Mineral Acid,

the sulphureous Acid having less affinity than any of the rest with

Alkalis. Nevertheless, this Salt becomes in time a true Vitriolated

Tartar, because the sulphureous part which weakened its Acid easily

quits it and flies off.

PROCESS VI.

_To concentrate the Vitriolic Acid._

Take the Vitriolic Acid you intend to concentrate, that is, to

dephlegmate and make stronger: pour it into a good glass retort, of

such a size that your quantity of Acid may but half fill it: set this

retort in the sand-bath of a reverberating furnace: fit to it a

receiver; lute it on, and give a gradual fire. There will come over

into the receiver a clear liquor, the first drops of which will be but

faintly acid: this is the most aqueous part.

When the drops begin to follow one another much more slowly, raise your

fire, till the liquor begin to bubble a little in the middle. Keep

it thus gently boiling, till one half or two thirds thereof be come

over into the receiver. Then let your vessels cool; unlute them; what

remains in the retort pour into a crystal bottle, and stop it exactly

with a glass stopple rubbed with emery.

_OBSERVATIONS._

The Acid obtained from Sulphur is generally very aqueous; either

because in preparing it water must necessarily be administered, that it

may unite therewith as it separates from the Sulphur; or because it is

so greedy of moisture as to attract a great deal from the air, which

must needs be admitted to make the Sulphur burn.

The Acid obtained from Vitriol, excepting that which rises last, is

also mixed with a pretty considerable quantity of phlegm; because

the Vitriol, though calcined, still retains a great deal thereof,

which rises with the Acid in distillation. Now, as there are many

chymical experiments that will not succeed without Acids exceedingly

dephlegmated, it is proper to have in a laboratory all the Acids thus

conditioned; because if they happen to be too strong for particular

operations, as is sometimes the case, it is very easy to lower them to

the desired degree, by adding a sufficient quantity of water.

The Vitriolic Acid is much heavier and much less volatile than water.

If therefore a mixture of these two liquors be exposed to the fire, the

aqueous part will rise with a degree of heat which is not able to carry

up the Acid: by this means they may be separated from each other; and

thus is the Vitriolic Acid concentrated.

Nevertheless, as this Acid combines most closely with water, and is in

a manner strongly connected with it, the water carries up some portion

thereof along with it; and hence it comes, that the liquor which rises

into the receiver is acid: it is called _Spirit of Vitriol_.

As the fire carries off the most aqueous part, the other which remains

in the retort increases in specific gravity. The Acid particles

are brought nearer together, retain the aqueous particles more

obstinately, and therefore to separate them the degree of heat must be

increased.

It is usual to draw off one half or two thirds of the liquor that was

put into the retort: but this depends on the degree of strength the

Acid was of before concentration, and the degree of concentration

intended to be given it.

If the Acid to be concentrated be Oil of Vitriol, from being brown or

black it grows clearer as the operation advances, and at last becomes

perfectly colourless and transparent; because the fat matter which

tinged it black is dissipated during the process. Some of it deposites

a white crystalline earth.

A sulphureous smell is generally perceived about the vessels in this

operation. This arises from a small portion of the Phlogiston from

which the Acid is not free; and it is this inflammable matter which

gives the Oil of Vitriol its black colour: for the clearest and best

rectified Oil of Vitriol will become brown, and even black, in a short

time, if any inflammable matter, though in a very small quantity, be

dissolved therein.

The vessels are luted in this operation, to prevent any loss of the

Spirit of Vitriol, which being very acid is of use in many chymical

experiments, and may itself also be again concentrated.

We observed, that in this operation it is necessary the retort should

be of very good glass. Indeed the Acid is so active, and so strong,

that if the glass be tender and have a little too much salt in its

composition, it will be so corroded thereby that it will fall to pieces.

Though we directed the retort to be set in a sand-bath for this

operation, it does not follow that it may not also be placed in a naked

fire: on the contrary, when the heat is not conveyed through a bath the

operation advances faster, and is much less tedious. But then great

caution must be used, and the closest attention given to the management

of the fire, which must be raised by almost imperceptible degrees,

especially at the beginning of the operation; otherwise it is next to a

certainty that the vessels will break. In general, a naked fire may be

employed in almost all distillations which require a greater degree of

heat than that of boiling water, or the _balneum mariæ_: the operation

will be sooner finished; but it requires an experienced hand, that has

by practice acquired a habit of governing the fire with judgment.

There is moreover another advantage in not using the sand-bath; which

is, that if in the time of the operation you perceive the fire too

fierce, you can quickly check it, either by stopping close all the

apertures of the furnace, or by drawing out all or part of the lighted

coals. This inconvenience is not near so easily remedied when you use

the sand-bath; because when once heated it retains its heat very long

after the fire is quite extinguished.

PROCESS VII.

_To decompose Vitriolated Tartar by means of the Phlogiston; or to

compose Sulphur by combining the Vitriolic Acid with the Phlogiston._

Take equal parts of Vitriolated Tartar, and very dry Salt of Tartar,

separately reduced to powder; add an eighth part of their weight of

charcoal-dust; and mix the whole together very accurately. Throw this

mixture into a red-hot crucible, placed in a furnace filled with

burning coals. Cover it very close, and keep it very hot; till the

mixture melt, which may be known by uncovering the crucible from time

to time. There will then appear a blueish flame, accompanied with a

pungent smell of Sulphur.

Take the crucible out of the fire: dissolve its contents in hot water:

filter the solution through brown paper supported by a glass funnel:

drop into the filtered liquor by little and little any Acid whatever.

As you add the acid the liquor will grow more and more turbid, and let

fall a grey precipitate. Continue dropping in more Acid till the liquor

will yield no more precipitate. Filter it a second time, to separate it

from the precipitate: what remains on the filter is a true inflammable

Sulphur, which you may either melt or sublime into flowers.

_OBSERVATIONS._

All bodies that contain the Vitriolic Acid may contribute, as well

as Vitriolated Tartar, to the generation of Sulphur: so that all the

neutral salts in which this Acid is a principle, the Alums, Selenites,

Gypsums, Vitriols, may be substituted for it in this experiment. All

these matters, with the addition of charcoal-dust only, being fused

in a crucible, constantly produce Sulphur; because the Vitriolic Acid

having a greater affinity with the Phlogiston than with any thing

else, will quit its basis, whatever it be, to join with the Phlogiston

of the charcoal, and therewith form a Sulphur.

The fixed Alkali added thereto helps to promote the fusion of the

ingredients, which is necessary for effecting the desired combination.

It also serves to unite with the Sulphur, when formed; and thus makes

the combination called _Liver of Sulphur_, which prevents the Sulphur

from being consumed as soon as formed: for the fixed Alkalis, which are

incombustible, hinder Sulphur from burning so easily as it would do if

they were not joined with it. They may afterwards be separated from

each other, by the means of any Acid whatever.

This process, in which Sulphur is regenerated by recombining together

the principles of which it was originally composed, is one of the most

beautiful experiments that modern Chymistry hath produced. We are

indebted for it to M. Stahl; and Dr. Geoffroy hath given a particular

account of it in the Memoirs of the Academy of Sciences.

Before these gentlemen Glauber and Boyle had indeed published methods

of producing Sulphur, Glauber made use of his _Sal mirabile_ and

powdered charcoal: Boyle employed the Vitriolic Acid and Oil of

Turpentine. But neither of those Chymists understood the true theory

of their operations: they did not thoroughly know the principles of

Sulphur: they did not imagine they had composed Sulphur: they thought

they only extracted what they supposed to exist previously in the

matters they employed in their experiments.

M. Stahl was the first who discovered and explained the nature of

Sulphur, and proved that in Glauber's and Boyle's experiments Sulphur

was actually produced, by uniting together the principles of which it

is constituted. This beautiful experiment gives the strongest lustre

of evidence to the theory of the composition of that mixt, which acts

such a capital part in Chymistry; and it can no longer be doubted,

that Sulphur is actually a combination of the Vitriolic Acid with the

Phlogiston.

Besides this important truth, our process for composing Sulphur by art

proves several others that are equally essential and fundamental.

The first is, that the Vitriolic Acid hath a greater affinity with

the Phlogiston than with any other thing, seeing it quits metallic

and earthy substances, as well as Alkaline salts, in order to combine

therewith.

The second is, that Sulphur combines with fixed Alkalis without

suffering any decomposition; seeing it may be separated from them

entire and unaltered; and seeing that very Sulphur, which is naturally

indissoluble in water, is rendered soluble therein by the union it hath

contracted with the fixed alkali.

The third is, that the Vitriolic Acid, which, when it is pure, hath the

greatest affinity with Alkalis of any Acid whatever, loses a great deal

of that affinity by contracting an union with the Phlogiston; seeing

the weakest acids are capable of decomposing the Liver of Sulphur, and

separating the Sulphur from the Alkali. And this also confirms one of

the general propositions concerning affinities advanced in our theory;

to wit, that the affinities of compound or mixed substances are weaker

than those of the same substances in a purer or more simple state.

CHAP. II.

_Of the_ NITROUS ACID.

PROCESS I.

_To extract Nitre out of nitrous Earths and Stones. The Purification

of Salt-petre. Mother of Nitre. Magnesia._

Take any quantity of nitrous earths or stones; reduce them to powder;

and therewith mix a third part of the ashes of green-wood and

quick-lime. Put this mixture into a barrel or vat, and pour on it hot

water to about twice the weight of the whole mass. Let it stand thus

for twenty-four hours, stirring it from time to time with a stick. Then

filter the liquor through brown paper, or pass it through a flannel

bag, till it come clear: it will then have a yellowish colour. Boil

this liquor, and evaporate till you perceive that a drop of it let fall

on any cold body coagulates. Then stop the evaporation, and set your

liquor in a cool place. In the space of four and twenty hours crystals

will be formed in it, the figure of which is that of an hexagonal

prism, having its opposite planes generally equal, and terminated at

each extremity by a pyramid of the same number of sides. These crystals

will be of a brownish colour, and deflagrate on a live coal.

Decant the liquor from these crystals; mix it with twice its weight

of hot water; evaporate and crystallize as before. Repeat the same

operation till the liquor will yield no more crystals: it will then be

very thick, and goes by the name of _Mother of Nitre_.

_OBSERVATIONS._

Earths and stones that have been impregnated with animal or vegetable

juices susceptible of putrefaction, and have been long exposed to the

air, but sheltered from the sun and rain, are those which yield the

greatest quantity of Nitre. But all sorts of earths and stones are not

equally fit to produce it. None is ever found in flints or sands of a

crystalline nature.

Some earths and stones abound so with Nitre, that it effloresces

spontaneously on their surface, in the form of a crystalline down. This

Nitre may be collected with brooms, and accordingly has the name of

_Salt-petre Sweepings_. Some of this sort is brought from India.

Hitherto we are much in the dark as to the origin and generation of

Nitre. Some Chymists pretend that the Nitrous Acid is diffused through

the air, and gradually deposited in such earths and stones as are

qualified to receive it.

Others, considering that none of it is ever obtained but from earths

that have been impregnated with vegetable or animal juices, have from

thence concluded those two kingdoms to be the general repositories

of the Nitrous Acid; that if we do not perceive it to exist in such

matters at all, or at least in any great quantity, till they have

undergone putrefaction, and are in some measure incorporated with

suitable earths and stones, it is because the Acid is so entangled

with heterogeneous particles that it requires the assistance of

putrefaction, and much more of filtration through an earth, to

disengage it, and enable it to appear in its proper nature.

Lastly, others are of opinion that this Acid is no other than the

universal or Vitriolic Acid; disguised indeed by a portion of the

Phlogiston, which is combined with it in a peculiar manner by the means

of putrefaction. They ground this opinion chiefly on the analogy or

resemblance which they find between the Nitrous Acid and the Volatile

Sulphureous Spirit. Its volatility, its pungent smell, its properties

of taking fire, and of destroying the blue and violet colours of

vegetables, serve them as so many proofs.

Their opinion is the more probable on this account, that even though

the Nitrous Acid should actually be produced by vegetable and animal

substances, yet as these substances themselves draw all their component

principles from the earth, and as the Vitriolic Acid is diffused

through all the soils which afford them nourishment, there is great

reason to think that the Nitrous Acid is no other than the Vitriolic

Acid altered by the changes and combinations it hath undergone in its

passage into and through those substances. In 1750 the Royal Academy

of Sciences at Berlin proposed an account of the generation of Nitre

as the subject for their prize, which was conferred on a Memoir

wherein this last opinion was supported by some new and very judicious

experiments.

The process by which our Salt-petre makers extract Nitre in quantities,

out of rubbish and nitrous earths, is very nearly the same with that

here set down; so that I shall not enter into a particular account

of it. I shall only take notice of one thing, which it is of some

consequence to know; namely, that there is no nitrous earth which does

not contain sea-salt also. The greatest quantities of this salt are to

be found in those earths which have been drenched with urine, or other

animal excrements. Now as the rubbish of old houses in great cities

is in this class, it comes to pass that when the Salt-petre workers

evaporate a nitrous lixivium drawn from that rubbish, as soon as the

evaporation is brought to a certain pitch, a great many little crystals

of sea-salt form in the liquor, and fall to the bottom of the vessel.

The Salt-petre workers in France call these saline particles _the

Grain_, and take care to separate them from the liquor (which, as

long as it continues hot, keeps the salt-petre dissolved) before they

set it to crystallize. This fact seems a little singular, considering

that sea-salt dissolves in water more easily than salt-petre, and

crystallizes with more difficulty.

In order to discover the cause of this phenomenon, we must recollect

some truths delivered in our theoretical Elements. The first is, that

water can keep but a determinate quantity of any salt in solution, and

that if water fully saturated with a salt be evaporated, a quantity

of salt will crystallize in proportion to the quantity of water

evaporated. The second is, that those salts which are the most soluble

in water, particularly those which run in the air, will dissolve in

cold and in boiling water equally; whereas much greater quantities of

the other salts will dissolve in hot and boiling water than in cold

water. These things being admitted, when we know that sea-salt is

one of the first sort, and salt-petre of the second, the reason why

sea-salt precipitates in the preparation of salt-petre appears at once.

For,

When the solution of Salt-petre and Sea-salt comes to be evaporated to

such a degree that it contains as much Sea-salt as it possibly can,

this salt must begin to crystallize, and continue to do so gradually

as the evaporation advances. But because at the same time it does not

contain as much salt-petre as it can hold, seeing it is capable of

dissolving a much greater quantity thereof when it is boiling hot than

when it is cold, this last-named salt will not crystallize so soon. If

the evaporation were continued till the case of the Salt-petre came to

be the same with that of the Sea-salt, then the salt-petre also would

begin to crystallize gradually in proportion to the water evaporated,

and the two salts will continue crystallizing promiscuously together:

but it is never carried so far; nor is it ever necessary: for, as the

water cools, it becomes more and more incapable of holding in solution

the same quantity of salt-petre as when it was boiling hot.

And then comes the very reverse, with regard to the crystallizing of

the two salts; for then the Salt-petre shoots, and not the Sea-salt.

The reason of this fact also is founded on what has just been said. The

Sea-salt, of which cold water will dissolve as much as boiling water,

and which owed its crystallizing before only to the evaporation, now

ceases to crystallize as soon as the evaporation ceases; while the

Salt-petre, which the water kept dissolved only because it was boiling

hot, is forced to crystallize merely by the cooling of the water.

When the solution of Salt-petre has yielded as many crystals of that

Salt as it can yield by cooling, it is again evaporated, and being

then suffered to cool yields more crystals. And thus they continue

evaporating and crystallizing, till the liquor will afford no more

crystals. It is plain that as the Salt-petre crystallizes, the

proportion of Sea-salt to the dissolving liquor increases; and as a

certain quantity of water evaporates also during the time employed in

crystallizing the Salt-petre, a quantity of Sea-salt, proportioned to

the water so evaporating, must crystallize in that time: and this is

the reason why Salt-petre is adulterated with a mixture of Sea-salt.

It likewise follows that the last crystals of Nitre, obtained from a

solution of Salt-petre and Sea-salt, contain much more Sea-salt than

the first.

From all that has been said concerning the crystallization of

Salt-petre and Sea-salt, it is easy to deduce the proper way of

purifying the former of these two Salts from a mixture of the latter.

For this purpose the Salt-petre to be refined need only be dissolved

in fair water. The proportion between the two salts in this second

solution is very different from what it was in the former; for it

contains no more Sea-salt than what had crystallized along with the

Salt-petre under favour of the evaporation, the rest having been left

dissolved in the liquor that refused to yield any more nitrous crystals.

As there is therefore a much greater quantity of Salt-petre than of

Sea-salt in this second solution, it is easy to evaporate it to such a

degree that a great deal of Salt-petre shall crystallize, while much

more of the water must necessarily be evaporated before any of the

Sea-salt will crystallize.

However, the Salt-petre is not yet entirely freed from all mixture of

Sea-salt by this first purification; for the crystals obtained from

this liquor, in which Sea-salt is dissolved, are still encrusted, and,

as it were, infected therewith: hence it comes, that, to refine the

Salt-petre thoroughly, these crystallizations must be repeated four or

five times.

The Salt-petre men commonly content themselves with crystallizing it

thrice, and call the produce Salt-petre of the first, second, or third

shoot, according to the number of crystallizations it has undergone.

But their best refined Salt-petre, even that of the third shooting, is

not yet sufficiently pure for Chymical experiments that require much

accuracy: so that it must be further purified; but still by the same

method.

The Nitrous Acid is not pure in the earths and stones from which it

is extracted. It is combined partly with the very earth in which

it is formed, and partly with the Volatile Alkali produced by the

putrefaction of the vegetable or animal matters that concurred to its

generation. A Fixed Alkali and Quick-lime are added to the lixivium

of a nitrous earth, in order to decompose the nitrous Salt formed in

that earth, and to separate the Acid from the Volatile Alkali and the

absorbent earth with which it is united: thence comes that copious

sediment which appears in the lye at the beginning of the evaporation.

These matters form with that Acid a true Nitre, much more capable than

the original Nitrous Salts of crystallization, detonation, and the

other properties which are essential thereto. The basis of Nitre is

therefore a Fixed Alkali mixed with a little lime.

The Mother of Nitre, which will yield no more crystals, is brown and

thick: by evaporation over a fire it is further inspissated, and

becomes a dry, solid body; which, however, being left to itself soon

gives, and runs into a liquor. This water still contains a good deal of

Nitre, Sea-salt, and the Acids of these Salts united with an absorbent

earth. It contains moreover a great deal of a fat, viscid matter, which

prevents its crystallizing.

All saline solutions in general, after having yielded a certain

quantity of crystals, grow thick, and refuse to part with any

more, though they still contain much Salt. They are all called

_Mother-waters_, as well as that which hath yielded Nitre. The

Mother-waters of different Salts may prove the subjects of curious and

useful inquiries.

If a Fixed Alkali be mixed with the Mother of Nitre, a copious white

precipitate immediately falls, which being collected and dried is

called _Magnesia_. This precipitate is nothing but the absorbent earth

that was united with the Nitrous Acid, together with a good deal of the

lime that was added, and was also united with that Acid, from which

they are now separated by the Fixed Alkali, according to the usual laws

of affinities.

The Vitriolic Acid poured upon Mother of Nitre causes many Acid vapours

to rise, which are a compound of the Nitrous and Marine Acids, that is,

an _Aqua Regia_. On this occasion also there falls a large quantity of

a white powder, which is still called _Magnesia_; yet it differs from

the former in that it is not, like it, a pure absorbent earth, but

combined with the Vitriolic Acid.

An _Aqua regis_ may also be drawn from nitrous earths by the force of

fire only, without the help of any additament.

PROCESS II.

_To decompose Nitre by means of the Phlogiston. Nitre fixed by

Charcoal._ Clyssus _of Nitre_. Sal Polychrestum.

Take the purest Salt-petre in powder; put it into a large crucible,

which it may but half fill; set the crucible in a common furnace,

and surround it with coals. When it is red-hot the Nitre will melt,

and become as fluid as water. Then throw into the crucible a small

quantity of charcoal-dust: the Nitre and the Charcoal will immediately

deflagrate with violence; and a great commotion will be raised,

accompanied with a considerable hissing, and abundance of black smoke.

As the charcoal wastes, the detonation will abate, and cease entirely

as soon as the coal is quite consumed.

Then throw into the crucible the same quantity of charcoal-dust as

before, and the same phenomena will be repeated. Let this coal also

be consumed: then add more, and go on in the same manner till you

can excite no further deflagration; always observing to let the

burning coal be entirely consumed before you add any fresh. When no

deflagration ensues, the matter contained in the crucible will have

lost much of its fluidity.

_OBSERVATIONS._

Nitre will not take fire, unless the inflammable matter added to it

be actually burning, or the Nitre itself red-hot, and so thoroughly

ignited, as immediately to kindle it. Therefore, if you would procure

the detonation of Nitre with charcoal, and make use of cold charcoal,

as in the process, the Nitre in the crucible must be red-hot, and in

perfect fusion: but you may also use live coals, and then the Nitre

need not be red-hot.

It is proper that the crucible used in this experiment should be only

half full; for during the detonation its contents swell, and might run

over without this precaution. For the same reason the charcoal-dust is

to be thrown in by little and little; and that first put in must be

entirely consumed before any fresh be added.

The matter remaining in the crucible after the operation is a very

strong Fixed Alkali. Being exposed to the air it quickly attracts the

moisture thereof, and runs into a liquor. It is called _Alkalizated

Nitre_, or, to distinguish it from Nitre alkalizated by other

inflammable matters, _Nitre fixed by charcoal_.

However, this Alkali is not absolutely pure. It still contains a

portion of the Nitre that hath not been decomposed. For when there

remains but a little of this salt mixed with a great quantity of

Alkali, which is not inflammable, the Alkali in some measure shelters

it, coats it over, and obstructs that immediate contact with the

inflammable matters applied, which is necessary to make it deflagrate.

If the Fixed Alkali be desired perfectly free from any mixture of

undecomposed Nitre, the fire about the crucible must be considerably

increased as soon as the detonation is entirely over; the matter must

be made to flow, which requires a much stronger heat than would melt

Nitre, and kept thus in fusion for about an hour. After this no perfect

Nitre will be found therein: for the little that was left, being unable

to abide the force of the fire, as not being extremely fixed, either

is entirely dissipated, or loses its Acid, which is carried off by the

violence of the heat.

Fixed Nitre contains also a portion of the earth that constituted the

basis of the Nitre, which is no other than the lime employed in its

crystallization, or else some of the earth with which its Acid was

originally combined, and which it retained in crystallizing. When Nitre

is deflagrated with such matters as produce ashes, these ashes likewise

furnish a certain quantity of earth, which mixes with the Fixed Alkali.

To separate these several earths from the Alkali, nothing more is

requisite than to let it run _per deliquium_, or to dissolve it in

water, and filter the solution through brown paper. Whatever is saline

will pass through the filtre with the water, and the earthy part will

be left upon it.

The Nitrous Acid is not only dissipated during the deflagration of the

Nitre, but is even destroyed, and perfectly decomposed. The smoke that

rises during the operation has not the least odour of an Acid. Its

nature may be accurately examined by catching it in proper vessels, and

condensing it into a liquor.

Nitre differs from Sulphur, and from all other inflammable bodies

whatever, in this, that the free access of the air is indispensably

necessary to make any of the others burn; whereas Nitre, and Nitre

only, is capable of burning in close vessels: and this property

furnishes us with the means of collecting the vapours which it

discharges in deflagration.

For this purpose, to a tubulated earthen retort you must fit two or

three large adopters: set the retort in a furnace; and under it make a

fire sufficient to keep its bottom moderately red. Then take a small

quantity, two or three pinches for example, of a mixture of three parts

of Nitre with one of charcoal-dust, and drop it into the retort through

its tube, which must be uppermost, and immediately stopped close.

A detonation instantly ensues, and the vapours that rise from the

inflamed mixture of Nitre and charcoal, passing out through the neck

of the retort into the adopters, circulate therein for a while, and at

last condense into a liquor.

When the detonation is over, and the vapours condensed, or nearly so,

drop into the retort another equal quantity of the mixture; and repeat

this till you find there is liquor enough in the recipients to be

examined with ease and accuracy. This liquor is almost insipid, and

shews no tokens of acidity; or at most but very slight ones. It is

called _Clyssus_ of Nitre.

It is easy to perceive why several adopters are required in this

experiment, and why a very small quantity of the mixture must be

introduced into the retort at once. The explosion, and the quantity of

air and vapours discharged on this occasion, would quickly burst the

vessels, if all these precautions were not attended to. This plainly

appears from the terrible effects of gun-powder, which is nothing but a

composition of Nitre, Sulphur, and Charcoal.

Nitre is also decomposed and takes fire by the means of Sulphur; but

the circumstances and the result differ widely from those produced

therewith by charcoal, or any other inflammable body.

Nitre deflagrates with Sulphur on account of the Phlogiston which the

latter contains. If one part of Sulphur be mixed with two or three

parts of Nitre, and the mixture thrown by little and little into a

red-hot crucible, upon every projection there arises a detonation

accompanied with a vivid flame.

The vapours discharged on this occasion have the mingled smell of

a Sulphureous Spirit and Spirit of Nitre; and if they be collected

by means of a tubulated retort, and such an apparatus of vessels as

was used in the preceding experiment, the liquor contained in the

recipients is found to be an actual mixture of the Acid of Sulphur, the

Sulphureous Spirit, and the Acid of Nitre; the first being in greater

quantity than the other two, and the second greater than the last.

Nor is the remainder after detonation a Fixed Alkali, as in the former

experiments; but a Neutral Salt, consisting of the Acid of Sulphur

combined with the Alkali of Nitre; a sort of Vitriolated Tartar known

in medicine by the name of _Sal Polychrestum_.

There are evidently two essential differences between this last

experiment and the preceding one. What remains after the deflagration

of Nitre with Sulphur is not a Fixed Alkali: and, moreover, the vapours

emitted in the operation are impregnated with a quantity of the Nitrous

Acid; which is not the case when Nitre is decomposed by any other

inflammable matter which contains no Vitriolic Acid.

The reason of these differences is naturally deducible from what hath

been already said concerning the properties of the Vitriolic and

Nitrous Acids. We have seen that by burning Sulphur its Acid is not

decomposed, but only separated from its Phlogiston. We also know,

that its Acid has a great affinity with Fixed Alkalis. These things

being granted, it follows that, as soon as the Nitrous Acid quits its

Alkaline basis, by deflagrating with the Phlogiston of the Sulphur, the

Acid of this very Sulphur, being set at liberty by that deflagration,

must unite with the Alkaline basis deserted by the Acid of Nitre, and

therewith form a Neutral Salt. Hence, instead of a Fixed Alkali, we

find at the end of the operation a sort of Vitriolated Tartar; the

Acids of Sulphur and of Vitriol being the same, as is evident from what

hath been above said concerning them.

In order to discover the cause of the other phenomenon, we must

recollect two things advanced in our Elements of the Theory; to wit,

that the affinity of the Vitriolic Acid with Fixed Alkalis is greater

than that of the Nitrous Acid; and again, that the Nitrous Acid is not

capable of combining and taking fire with the Phlogiston, but when it

is in the form of a Neutral Salt, that is, when it is united with some

alkaline, earthy, or metallic basis. If these two principles be applied

to the effect in question, the solution is easy and natural. For, in

the deflagration of Nitre with Sulphur, the Phlogiston is not the only

substance capable of separating the Nitrous Acid from its basis: the

Acid of the Sulphur, more and more of which is set at liberty as the

Phlogiston is consumed, is also capable of producing the same effect;

but with this difference, that the portion of the Nitrous Acid which is

detached from its Alkali by the Phlogiston is at the same instant set

on fire and decomposed by that union; whereas the portion thereof which

is separated by the Vitriolic Acid, being when so separated incapable

of uniting with the Phlogiston, and of consuming therewith, is

preserved entire, and rises in vapours, together with that portion of

the Vitriolic Acid which could not unite with the basis of the Nitre.

PROCESS III.

_To decompose Nitre by means of the Vitriolic Acid. The Smoking Spirit

of Nitre._ Sal de duobus. _The Purification of Spirit of Nitre._

Take equal parts of well purified Nitre and Green Vitriol: dry the

Nitre thoroughly, and bruise it to a fine powder. Calcine the Vitriol

to redness: reduce it likewise to a very fine powder; and mingle

these two substances well together. Put the mixture into an earthen

long-neck, or a good glass retort coated, of such a size that it may be

but half full.

Set this vessel in a reverberating furnace covered with its dome; apply

a large glass receiver, having a small hole in its body, stopped with

a little lute. Let this receiver be accurately luted to the retort

with the fat lute, and the joint covered with a slip of canvas smeared

with lute made of quick-lime and the white of an egg. Heat the vessels

very gradually. The receiver will soon be filled with very dense red

vapours, and drops will begin to distil from the nose of the retort.

Continue the distillation, increasing the fire a little when you

observe the drops to follow each other but slowly, so that above two

thirds of a minute passes between them; and, in order to let out the

redundant vapours, open the small hole in the receiver from time to

time. Towards the end of the operation raise the fire so as to make

the retort red. When you find that, even when the retort is red-hot,

nothing more comes over, unlute the receiver, and without delay pour

the liquor it contains into a crystal bottle, and close it with a

crystal stopple ground in its neck with emery. This liquor will be of a

reddish yellow colour, smoking exceedingly, and the bottle containing

it will be constantly filled with red fumes like those observed in the

receiver.

_OBSERVATIONS._

The Vitriolic Acid having a greater affinity with Fixed Alkalis than

with any other substance, the Phlogiston excepted, and being in the

Vitriol united with a ferruginous basis, will naturally quit that basis

to join with the Fixed Alkali of the Nitre; the Acid whereof being

weaker than the Vitriolic, as we have already observed on several

occasions, must needs be thereby expelled from its basis. The Nitre

therefore is decomposed by the Vitriol, and its Acid being set at

liberty, is carried up by the force of the fire.

Indeed the Nitrous Acid, being thus separated from its alkaline

basis, might be expected to combine with the ferruginous basis of

the Vitriol: but as it has, like all other Acids, much less affinity

with Metallic substances than with Alkalis, even a moderate degree of

fire is sufficient to separate it from them. Moreover, this Acid hath

either no effect, or very little, upon iron that has lost much of its

Phlogiston by contracting an union with any Acid; which is the case of

the ferruginous basis of Vitriol.

By the process here delivered a very strong, perfectly dephlegmated,

and vastly smoking Spirit of Nitre is obtained. If the precautions of

drying the Nitre and calcining the Vitriol be neglected, the Acid that

comes over, greedily attracting the water contained in these salts,

will be very aqueous, will not smoke, and will be almost colourless,

with a very slight tinge of lemon.

The fumes of highly concentrated Spirit of Nitre, such as that obtained

by the above process, are light, corrosive, and very dangerous to the

lungs; being no other than the most dephlegmated part of the Nitrous

Acid. The person therefore who unlutes the vessels, or pours the liquor

out of the receiver into the bottle, ought with the greatest caution

to avoid drawing them in with his breath; and for that reason ought to

place himself so that a current of air, either natural or artificial,

may carry them off another way. It is also necessary that care be

taken, during the operation, to give the vapours a little vent every

now and then, by opening the small hole in the recipient; for they are

so elastic, that, if too closely confined, they will burst the vessels.

When the operation is over, you will find a red mass at the bottom of

the retort, cast, as it were, in a mould. This is a Neutral Salt of the

nature of Vitriolated Tartar, resulting from the union of the Acid of

the Vitriol with the Alkaline basis of the Nitre.

The ferruginous basis of the Vitriol, which is mixed with this salt,

gives it the red colour. To separate it therefrom, you must pulverise

it, dissolve it in boiling water, and filter the solution several times

through brown paper; because the ferruginous earth of the Vitriol is

so fine, that some of it will pass through the first time. When the

solution is very clear, and deposites no sediment, let it be set to

shoot, and it will yield crystals of Vitriolated Tartar; to which

Chymists have given the peculiar title of _Sal de duobus_.

In this _Caput mortuum_ we frequently find, besides the ferruginous

earth of Vitriol, a portion of Nitre and Vitriol not decomposed; either

because the two salts were not thoroughly mingled, or because the fire

was not raised high enough towards the end of the operation.

Nitre may also be decomposed, and its acid obtained, by the

interposition of any of the other Vitriols, Alums, Gypsums, Boles,

Clays; in short, by means of any compound in which the Vitriolic Acid

is found, provided it have not a Fixed Alkali for its basis.

The distillers of _Aqua fortis_, who make large quantities at a time,

and who use the least chargeable methods, do their business by the

means of earths impregnated with the Vitriolic Acid; such as Clays

and Boles. With these earths they accurately mix the Nitre from which

they intend to draw their Spirit: this mixture they put into large

oblong earthen pots, having a very short curved neck, which enters a

recipient of the same matter and form. These vessels they place in two

rows opposite to each other in long furnaces, and cover them over with

bricks cemented with Windsor-loam, which serves for a reverberatory:

then they light the fire in the furnace, making it at first very small,

only to warm the vessels; after which they throw in wood, and raise the

fire till the pots grow quite red-hot, in which degree they keep it up

till the distillation is entirely finished.

The Acid of Nitre may also be separated from its basis by means of the

pure Vitriolic Acid. For this purpose the Nitre from which you mean to

extract the Acid must be finely pulverized, put into a glass retort,

and a third of its weight of concentrated Oil of Vitriol poured on it:

the retort must be placed in a reverberating furnace, and a receiver,

like that used in the preceding operation, expeditiously applied.

As soon as the Oil of Vitriol touches the Nitre the mixture grows hot,

and copious red fumes begin to appear: some drops of the Acid come over

even before the fire is kindled in the furnace.

On this occasion the fire must be moderate; because the Vitriolic Acid,

being clogged by no basis, acts upon the Nitre much more briskly, and

with much greater effect, than when it is not pure.

This operation may be performed by a sand-heat; which is a speedy and

commodious way of obtaining the Nitrous Acid. In other respects the

precautions recommended in the preceding experiment must be carefully

observed here, both in distilling the Acid and in taking it out of the

receiver.

The Spirit of Nitre extracted by this method is as strong, and smokes

as much, as that obtained by calcined Vitriol, provided the Oil of

Vitriol made use of be well concentrated; but it is generally tainted

by the admixture of a small portion of the Vitriolic Acid, which,

having no basis of its own to restrain it, is carried up by the heat

before it can lay hold of the basis of the Nitre.

There are several experiments in Chymistry that succeed equally well

whether the Nitrous Acid be or be not thus adulterated with a mixture

of the Vitriolic Acid; but there are some, as we shall see, that

will not succeed without a Spirit of Nitre so mixed. If the Acid be

distilled with a view to such experiments, it must be kept as it is.

But most experiments require the Spirit of Nitre to be absolutely pure;

and if it be intended for such, it must be perfectly cleansed from the

Vitriolic taint.

This is easily effected by mixing your Spirit with very pure Nitre,

and distilling it a second time. The Vitriolic Acid, with which this

Spirit of Nitre is adulterated, coming in contact with a great quantity

of undecomposed Nitre, unites with its Alkaline basis, and expels a

proportionable quantity of the Nitrous Acid.

In the retort made use of to distil the Nitrous Acid, by means of the

pure Vitriolic Acid, is found a _Caput mortuum_, differing from that

left after the distillation of the same Acid by the interposition of

Vitriol, in as much as it contains no red ferruginous earth. This is

a very white saline mass, moulded in the bottom of the retort: if you

pound it, dissolve it in boiling water, and evaporate the solution,

it will shoot into crystals of Vitriolated Tartar: sometimes also

it contains a portion of undecomposed Nitre, which shoots after the

Vitriolated Tartar, because it is much more soluble in water.

CHAP. III.

_Of the_ MARINE ACID.

PROCESS I.

_To extract Sea-salt from Sea-water, and from Brine-springs. Epsom

Salt._

Filter the salt-water from which you intend to extract the salt:

evaporate it by boiling till you see on its surface a dark pellicle:

this consists wholly of little crystals of salt just beginning to

shoot: now slacken the fire, that the brine may evaporate more slowly,

and without any agitation. The crystals, which at first were very

small, will become larger, and form hollow truncated pyramids, the

apices whereof will point downwards, and their bases be even with the

surface of the liquor.

These pyramidal crystals are only collections of small cubical crystals

concreted into this form. When they have acquired a certain magnitude

they fall to the bottom of the liquor. When they come to be in such

heaps as almost to reach the surface of the liquor, decant it from

them, and continue the evaporation till no more crystals of Sea-salt

will shoot.

_OBSERVATIONS._

The Acid of Sea-salt is scarce ever found, either in sea-water or in

the earth, otherwise than united with a fixed alkali of a particular

kind, which is its natural basis; and consequently it is in the form of

a Neutral Salt. This salt is plentifully dissolved in the waters of the

ocean, and when obtained therefrom bears the name of _Sea-salt_. It is

also found in the earth in vast crystalline masses, and is then called

_Sal-gem_: so that Sea-salt and Sal-gem are but one and the same sort

of salt, differing very little from each other, except as to the places

where they are found.

In the earth are also found springs and fountains, whose waters are

strong brines, a great deal of Sea-salt being dissolved in them. These

springs either rise directly from the sea, or run through some mines

of Sal-gem, of which they take up a quantity in their passage.

As the same, or at least nearly the same, quantity of Sea-salt will

continue dissolved in cold water as boiling water will take up, it

cannot shoot, as Nitre does, by the mere cooling of the water in which

it is dissolved: it crystallizes only by the means of evaporation,

which continually lessens the proportion of the water to the salt; so

that it is always capable of containing just so much the less Sea-salt

the more there is crystallized.

The brine should not boil after you perceive the pellicle of little

crystals beginning to form on its surface; for the calmness of the

liquor allows them to form more regularly, and become larger. Nor after

this should the evaporation be hurried on too fast; for a saline crust

would form on the liquor, which, by preventing the vapours from being

carried off, would obstruct the crystallization.

If the evaporation be continued after the liquor ceases to yield any

crystals of Sea-salt, other crystals will be obtained of an oblong

four-sided form, which have a bitter taste, and are almost always

moist. This sort of salt is known by the name of _Epsom Salt_, which

it owes to a salt spring in England, from the water of which it was

first extracted. This salt, or rather saline compound, is a congeries

of Glauber's salt and Sea-salt, in a manner confounded together, and

mixed with some of the Mother of Sea-salt, in which is contained a

kind of bituminous matter. These two Neutral Salts, which constitute

the Epsom Salt, may be easily separated from each other, by means of

crystallization only. Epsom Salt is purgative and bitter; and therefore

named _Sal Catharticum Amarum_, or bitter purging Salts.

There are different methods used in great works for obtaining Sea-salt

out of water in which it is dissolved. The simplest and easiest is that

practised in France, and in all those countries which are not colder.

On the sea-shore they lay out a sort of broad shallow pits, pans, or

rather ponds, which the sea fills with the tide of flood. When the

ponds are thus filled, they stop their communication with the sea, and

leave the water to evaporate by the heat of the sun; by which means

all the salt contained in it necessarily crystallizes. These pits are

called _Salt Ponds_. Salt can be made in this way in the summer-time

only; at least in France, and other countries of the same temperature:

for during the winter, when the sun has less power and rains are

frequent, this method is not practicable.

For this reason, as it often rains in the province of Normandy, the

inhabitants take another way to extract Salt from sea-water. The

labourers employed for this purpose raise heaps of sand on the shore,

so that the tide waters and drenches them when it flows, and leaves the

sand dry when it ebbs. During the interval between two tides of flood

the sun and the air easily carry off the moisture that was left, and

so the sand remains impregnated with all the salt that was contained

in the evaporated water. Thus they let it acquire as much salt as it

can by several returns of flood, and then wash it out with fresh water,

which they evaporate over a fire in leaden boilers.

To obtain the Salt from brine-springs, the water need only be

evaporated: but as several of these springs contain too little salt

to pay the charges that would be incurred, if the evaporation were

effected by the force of fire only, the manufacturers have fallen upon

a less expensive method of getting rid of the greatest part of the

water, and preparing the brine for crystallization, in much less time,

and with much less fire, than would otherwise have been necessary.

The method consists in making the water fall from a certain heighth on

a great many small spars of wood, which divide it into particles like

rain. This is performed under sheds open to all the winds, which pass

freely through this artificial shower. By this means the water presents

to the air a great extent of surface, being indeed reduced almost

entirely to surface, and the evaporation is carried on with great ease

and expedition. The water is raised by pumps to the heighth from which

it is intended to fall[6].

[6] The Marquis de Montalembert, in a Memoir read before the Academy

of Sciences, proposes a new method of effecting these evaporations,

together with some considerable improvements in the structure and

disposition of the buildings necessary for that purpose. They are

called by the French _Batiments de Graduation_; which may properly

enough be rendered _Brine-houses_.

PROCESS II.

_Experiments concerning the decomposition of Sea-salt, by means of the

Phlogiston._ Kunckel_'s Phosphorus_.

"Of pure urine that has fermented five or six days take a quantity

in proportion to the quantity of phosphorus you intend to make:

it requires about one third part of a hogshead to make a dram of

Phosphorus. Evaporate it in iron pans, till it become clotted, hard,

black, and nearly like chimney-soot; at which time it will be reduced

to about a sixtieth part of its original weight before evaporation.

"When the urine is brought to this condition put it in several portions

into so many iron pots, under which you must keep a pretty brisk fire

so as to make their bottoms red, and stir it incessantly till the

volatile salt and the fetid oil be almost wholly dissipated, till the

matter cease to emit any smoke, and till it smell like peach-blossoms.

Then put out the fire, and pour on the matter, which will now be

reduced to a powder, somewhat more than twice its weight of warm

water. Stir it about in this water, and leave it to soak therein for

twenty-four hours. Pour off the water by inclination; dry the drenched

matter, and pulverize it. The previous calcination carries off from the

matter about a third of its weight, and the lixiviation washes out half

the remainder.

"With what remains thus calcined, washed, and dried, mix half its

weight of gravel, or yellow freestone rasped, having sifted out and

thrown away all the finest particles. River sand is not proper on this

occasion, because it flies in a hot fire. Then add to this mixture a

sixteenth part of its weight of charcoal, made of beech, or of any

other wood except oak, because that also flies. Moisten the whole

with as much water as will bring it to a stiff paste, by working and

kneading it with your hands: now introduce it into your retort, taking

care not to daub its neck. The retort must be of the best earth, and of

such a size, that when your matter is in it, a full third thereof shall

still be empty.

"Place your retort, thus charged, in a reverberating furnace, so

proportioned, that there may be an interval of two inches all round

between the sides of the furnace and the bowl of the retort, even where

it contracts to form the neck, which should stand inclined at an angle

of sixty degrees. Stop all the apertures of the furnace, except the

doors of the fire-place and ash-hole.

"Fit on to the retort a large glass ballon two thirds full of water,

and lute them together, as in distilling the Smoking Spirit of Nitre.

In the hinder part of this ballon, a little above the surface of the

water, a small hole must be bored. This hole is to be stopped with a

small peg of birch-wood, which must slip in and out very easily, and

have a small knob to prevent its falling into the ballon. This peg

is to be pulled out from time to time, that by applying the hand to

the hole it may be known whether the air, rarefied by the head of the

retort, issues out with too much or too little force.

"If the air rushes out with too much rapidity, and with a hissing

noise, the door of the ash-hole must be entirely shut, in order to

slacken the fire. If it do not strike pretty smartly against the

hand, that door must be opened wider, and large coals thrown into the

fire-place to quicken the fire immediately.

"The operation usually lasts four and twenty hours; and the following

signs shew that it will succeed, provided the retort resist the fire.

"You must begin the operation with putting some unlighted charcoal in

the ash-hole, and a little lighted charcoal at the door thereof, in

order to warm the retort very slowly. When the whole is kindled, push

it into the ash-hole, and close the door thereof with a tile. This

moderate heat brings over the phlegm of the mixture. The same degree of

fire must be kept up four hours, after which some coals may be laid on

the grate of the fire-place, which the fire underneath will kindle by

degrees. With this second heat brought nearer the retort, the ballon

grows warm, and is filled with white vapours, which have the smell of

fetid oil. In four hours after, this vessel will grow cool and clear;

and then you must open the door of the ash-hole one inch, throw fresh

coals into the fire-place every three minutes, and every time shut the

door of it, lest the cold air from without should strike against the

bottom of the retort and crack it.

"When the fire has been kept up to this degree for about two hours, the

inside of the ballon begins to be netted over with a volatile salt of a

singular nature, which cannot be driven up but by a very violent fire,

and which smells pretty strong of peach-kernels. Care must be taken

that this concrete salt do not stop the little hole in the ballon: for

in that case it would burst, the retort being then red-hot, and the

air exceedingly rarefied. The water in the ballon, being heated by the

vicinity of the furnace, exhales vapours which dissolve this sprigged

salt, and the ballon clears up in half an hour after it has ceased

rising.

"In about three hours from the first appearance of this salt, the

ballon is again filled with new vapours, which smell like Sal Ammoniac

thrown upon burning coals. They condense on the sides of the receiver

into a salt which is not branched like the former, but appears in long

perpendicular streaks, which the vapours of the water do not dissolve.

These white vapours are the fore-runners of the Phosphorus, and a

little before they cease to rise they lose their first smell of Sal

Ammoniac, and acquire the odour of garlic.

"As they ascend with great rapidity, the little hole must be frequently

opened, to observe whether the hissing be not too strong: for, in that

case, it would be necessary to shut the door of the ash-hole quite

close. These white vapours continue two hours. When you find they cease

rising, make a small passage through the dome, by opening

some of its registers, that the flame may just begin to draw. Keep up

the fire in this mean state till the first volatile Phosphorus begin to

appear.

"This appears in about three hours after the white vapours first begin

to rise. In order to discover it, pull out the little birchen peg once

every minute, and rub it against some hot part of the furnace, where it

will leave a trail of light, if there be any Phosphorus upon it.

"Soon after you observe this sign, there will issue out through the

little hole of the ballon a stream of blueish light, which continues of

a greater or shorter extent to the end of the operation. This stream or

spout of light does not burn. If you hold your finger against it for

twenty or thirty seconds, the light will adhere to it; and if you rub

that finger over your hand, the light will besmear it, and render it

luminous.

"But from time to time this streamer darts out to the length of seven

or eight inches, snapping and emitting sparks of fire; and then it

burns all combustible bodies that come in its way. When you observe

this, you must manage the fire very warily, and shut the door of the

ash-hole quite close, yet without ceasing to throw coals into the

fire-place every two minutes.

"The Volatile Phosphorus continues two hours; after which the little

spout of light contracts to the length of a line or two: and now is the

time for pushing your fire to the utmost: immediately set the door of

the ash-hole wide open, throw billets of wood into it, unstop all the

registers of the reverberatory, supply the fire-place with large coals

every minute: in short, for six or seven hours all the inside of the

furnace must be kept of a white heat, so that the retort shall not be

distinguishable.

"In this fierce extremity of heat the true Phosphorus distils like an

oil, or like melted wax: one part thereof floats on the water in the

recipient, the other falls to the bottom. At last, the operation is

known to be quite over when the upper part of the ballon, in which the

volatile Phosphorus appears condensed in a blackish film, begins to

grow red: for this shews that the Phosphorus is burnt where the red

spot appears. You must now stop all the registers, and shut all the

doors of the furnace, in order to smother the fire; and then close

up the little hole in the ballon with fat lute or bees-wax. In this

condition the whole must be left for two days; because, the vessels

must not be separated till they are perfectly cold, lest the Phosphorus

should take fire.

"As soon as the fire is out, the ballon, which is then in the dark,

presents a most agreeable object: all the empty part thereof above

the water seems filled with a beautiful blue light: which continues

for seven or eight hours, or as long as the ballon keeps warm, never

disappearing till it is cooled.

"When the furnace is quite cold take out the vessels, and separate them

from each other as neatly as possible. With a linen cloth wipe away

all the black stuff you find in the mouth of the ballon; for if that

filth should mix with the Phosphorus, it would hinder it from being

transparent when moulded. This must be done with great expedition:

after which pour into the ballon two or three quarts of cold water, to

accelerate the precipitation of the Phosphorus that swims at top. Then

agitate the water in the ballon, to rinse out all the Phosphorus that

may stick to the sides: pour out all the water thus shaken and turbid,

into a very clean earthen pan, and let it stand till it grows clear.

Then decant this first useless water, and on the blackish sediment,

left at the bottom of the pan, pour some boiling water to melt the

Phosphorus; which thereupon unites with the fuliginous matter, or

volatile Phosphorus, that precipitated with it, both together forming a

mass of the colour of slate. When this water, in which you have melted

the Phosphorus, is cool enough, take out the Phosphorus, throw it into

cold water, and therein break it into little bits in order to mould it.

"Then take a matras, having a long neck somewhat wider next the body

than at its mouth: cut off half the body, so as to make a funnel of

the neck-part, the smaller end of which must be stopped with a cork.

The first mould being thus prepared, plunge it endwise, with its

mouth uppermost, in a vessel full of boiling water, and fill it with

that water. Into this funnel throw the little bits of your slate-like

mass, which will melt again in this hot water, and fall so melted to

the bottom of the tube. Stir this melted matter with an iron wire, to

promote the separation of the Phosphorus from the fuliginous matter

with which it is fouled, and which, being less ponderous than the

Phosphorus, will gradually rise above it towards the upper part of the

cylinder.

"Keep the water in the vessel as hot as at first, till, on taking out

the tube, you see the Phosphorus clean and transparent. Let the clear

tube cool a little, and then set it in cold water, where the Phosphorus

will congeal as it cools. When it is perfectly congealed, pull out the

cork, and with a small rod, near as big as the tube, push the cylinder

of Phosphorus towards the mouth of the funnel, where the feculency

lies. Cut off the black part of the cylinder, and keep it apart: for

when you have got a quantity thereof, you may melt it over again in the

same manner, and separate the clean Phosphorus which it still contains.

As to the rest of the cylinder which is clean and transparent, if you

intend to mould it into smaller cylinders, you may cut it in slices,

and melt it again by the help of boiling water in glass tubes of

smaller dimensions."

_OBSERVATIONS._

This process for making Phosphorus is copied from the Memoirs of the

Academy of Sciences for the Year 1737; where it is described by M.

Hellot, with so much accuracy, clearness, and precision, that I thought

I could not do better than transcribe it, without departing from the

author's own expressions, for the sake of such as may not have those

Memoirs. We shall take occasion, in these observations, to point out

some essential circumstances which I have omitted in the description

of the Process, that I might not break the connection between the

phenomena that happen in the course of this experiment.

It is proper to observe, in the first place, that one of the most usual

causes of miscarriage in this operation is a defect of the requisite

qualities in the retort employed. It is absolutely necessary to have

that vessel made of the best earth, and so well made that it shall be

capable of resisting the utmost violence of fire, continued for a very

long time; as appears by the description of the process. The retorts

commonly sold by potters, and other earthen-ware men, are not fit for

this operation; and M. Hellot was obliged to send to Hesse-Cassel for

such as he wanted.

We shall, in the second place, observe with M. Hellot, that, "before

you set your retort in the furnace, it is proper to make an essay of

your matter, to see if there be reason to hope for success. For this

purpose put about an ounce thereof into a small crucible, and heat it

till the vessel be red. The mixture, after having smoked, ought to chop

or crack without puffing up, or even rising in the least. From these

cracks will issue undulating flames, white and blueish, darting upwards

with rapidity. This is the first volatile Phosphorus, which occasions

all the danger of the operation. When these first flashes are over,

increase the heat of your matter by laying a large live coal upon the

crucible. You will then see the second Phosphorus, like a luminous,

steady vapour, of a colour inclining to violet, covering the whole

surface of the matter: it continues for a very long time, and diffuses

a smell of garlic, which is the distinguishing odour of the Phosphorus

you are seeking.

"When this luminous vapour is entirely gone, pour the red hot matter

out of the crucible upon an iron plate. If you do not find one drop of

salt in fusion, but that, on the contrary, the whole falls readily into

powder, it is a proof that your matter was sufficiently lixiviated, and

that it contains no more fixed Salt, or Sea-salt, if you will, than

is requisite. If you find on the plate a drop of salt coagulated, it

shews that there is too much left in, and that there is danger of your

miscarrying in the operation; because the redundant salt would corrode,

and eat through the retort. In this case your matter must be washed

again, and then sufficiently dried."

Our third observation shall be concerning the furnace proper to be

employed in this operation. This furnace must be so constructed, that,

within a narrow compass it may give a heat at least equal to that of

a glass-house furnace, or rather greater, especially during the last

seven or eight hours of the operation. M. Hellot in his Memoir gives an

exact description of such a furnace.