Set on the boiling-pot with 8 gallons of oil; kindle the fire; then lay
the fire in the gum-furnace; have as many 8lb. bags of gum-copal all
ready weighed up, as will be wanted; put one 8lb. into the pot, put fire
to the furnace, set on the gum-pot; in three minutes (if the fire is
brisk) the gum will begin to fuse and give out its gas, steam, and acid;
stir and divide the gum, and attend to the rising of it, as before
directed. 8lbs. of copal take in general from sixteen to twenty minutes
in fusing, from the beginning till it gets clear like oil, but the time
depends very much on the heat of the fire, and the attention of the
operator. During the first twelve minutes, while the gum is fusing, the
assistant must look to the oil, and bring it to a smart simmer; for it
ought to be neither too hot, nor yet too cold, but in appearance
beginning to boil, which he is strictly to observe, and, when ready, to
call out, “Bear a hand!” Then immediately both lay hold of a handle of
the boiling-pot, lift it right up, so as to clear the plate, carry it
out and place it on the ash-bed, the maker instantly returning to the
gum-pot, while the assistant puts three copper ladlefuls of oil into the
copper pouring-jack, bringing it in and placing it on the iron plate at
the back of the gum-pot to keep hot until wanted. When the maker finds
the gum is nearly all completely fused, and that it will in a few
minutes be ready for the oil, let him call out, “Ready oil!” The
assistant is then to lift up the oil-jack with both hands, one under the
bottom and the other on the handle, laying the spout over the edge of
the pot, and wait until the maker calls out, “Oil!” The assistant is
then to pour in the oil as before directed, and the boiling to be
continued until the oil and gum become concentrated, and the mixture
looks clear on the glass; the gum-pot is now to be set upon the
brick-stand until the assistant puts three more ladlefuls of hot oil
into the pouring-jack, and three more into a spare tin for the third run
of gum. There will remain in the boiling-pot still 3-1/2 gallons of oil.
Let the maker put his right hand down the handle of the gum-pot near to
the side, with his left hand near the end of the handle, and with a firm
grip lift the gum-pot, and deliberately lay the edge of the gum-pot over
the edge of the boiling-pot until all its contents run into the
boiling-pot. Let the gum-pot be held, with its bottom turned upwards,
for a minute right over the boiling-pot. Observe, that whenever the
maker is beginning to pour, the assistant stands ready with a thick
piece of old carpet, without holes, and sufficiently large to cover the
mouth of the boiling-pot should it catch fire during the pouring, which
will sometimes happen if the gum-pot is very hot; should the gum-pot
fire, it has only to be kept bottom upwards, and it will go out of
itself; but if the boiling-pot should catch fire, during the pouring,
let the assistant throw the piece of carpet quickly over the blazing
pot, holding it down all round the edges; in a few minutes it will be
smothered. The moment the maker has emptied the gum-pot, he throws into
it half a gallon of turpentine, and with the _swish_ immediately washes
it from top to bottom, and instantly empties it into the flat tin jack:
he wipes the pot dry, and puts in 8lbs. more gum, and sets it upon the
furnace; proceeding with this run exactly as with the last, and
afterwards with the third run. There will then be 8 gallons of oil and
24lbs. of gum in the boiling-pot, under which keep up a brisk strong
fire until a scum or froth rises and covers all the surface of the
contents, when it will begin to rise rapidly. Observe, when it rises
near the rivets of the handles, carry it from the fire, and set it on
the ash-bed, stir it down again, and scatter in the driers by a little
at a time; keep stirring, and if the frothy head goes down, put it upon
the furnace, and introduce _gradually_ the remainder of the driers,
always carrying out the pot when the froth rises near the rivets. In
general, if the fire be good, all the time a pot requires to boil, from
the time of the last gum being poured in, is about three and a half or
four hours; but _time_ is no criterion for a beginner to judge by, as it
may vary according to the weather, the quality of the oil, the quality
of the gum, the driers, or the heat of the fire, &c.; therefore, about
the third hour of boiling, try it on a bit of glass, and keep it boiling
until it feels strong and stringy between the fingers; it is then boiled
sufficiently to carry it on the ash-bed, and to be stirred down until it
is cold enough to mix, which will depend much on the weather, varying
from half an hour, in dry frosty weather, to one hour in warm summer
weather. Previous to beginning to mix, have a sufficient quantity of
turpentine ready, fill the pot, and pour in, stirring all the time at
the top or surface, as before directed, until there are fifteen gallons,
or five tins of oil of turpentine introduced, which will leave it quite
thick enough if the gum is good, and has been well run; but if the gum
was of a weak quality, and has not been well fused, there ought to be no
more than twelve gallons of turpentine mixed, and even that may be too
much. Therefore, when twelve gallons of turpentine have been introduced,
have a flat saucer at hand, and pour into it a portion of the varnish,
and in two or three minutes it will show whether it is too thick; if not
sufficiently thin, add a little more turpentine, and strain it off
quickly. As soon as the whole is stored away, pour in the turpentine
washings, with which the gum-pots have been washed, into the
boiling-pot, and with the swish quickly wash down all the varnish from
the pot sides; afterwards, with a large piece of woollen rag dipped in
pumice-powder, wash and polish every part of the inside of the
boiling-pot, performing the same operation on the ladle and stirrers;
rinse them with the turpentine washings, and at last rinse them
altogether in clean turpentine, which also put to the washings; wipe dry
with a clean soft rag the pot, ladle, stirrer, and funnels, and lay the
sieve so as to be completely covered with turpentine, which will always
keep it from gumming up. The foregoing directions concerning running the
gum, and pouring in the oil, and also boiling off and mixing, are, with
very little difference, to be observed in the making of all sorts of
copal varnishes, except the differences of the quantities of oil, gum,
&c., which will be found under the various descriptions by name, which
will be hereafter described.
The choice of linseed oil is of peculiar consequence to the
varnish-maker. Oil from fine full-grown ripe seed, when viewed in a
phial, will appear limpid, pale, and brilliant; it is mellow and sweet
to the taste, has very little smell, is specifically lighter than impure
oil, and, when clarified, dries quickly and firmly, and does not
materially change the colour of the varnish when made, but appears
limpid and brilliant.
_Copal varnishes for fine paintings, &c._--Fuse 8 lbs. of the very
cleanest pale African gum copal, and, when completely run fluid, pour in
two gallons of hot oil, old measure; let it boil until it will string
very strong; and in about fifteen minutes, or while it is yet very hot,
pour in three gallons of turpentine, old measure, and got from the top
of a cistern. Perhaps during the mixing, a considerable quantity of the
turpentine will escape; but the varnish will be so much the brighter,
transparent, and fluid; and will work freer, dry more quickly, and be
very solid and durable when dry. After the varnish has been strained, if
it is found too thick, before it is quite cold, heat as much turpentine,
and mix with it, as will bring it to a proper consistence.
_Cabinet varnish._--Fuse 7 lbs. of very fine African gum copal, and pour
in half a gallon of pale clarified oil; in three or four minutes after,
if it feel stringy, take it out of doors, or into another building where
there is no fire, and mix with it three gallons of turpentine;
afterwards strain it, and put it aside for use. This, if properly
boiled, will dry in ten minutes; but if too strongly boiled, will not
mix at all with the turpentine; and _sometimes_, when boiled with the
turpentine, will mix, and yet refuse to incorporate with any other
varnish less boiled than itself: therefore it requires a nicety which is
only to be learned from practice. This varnish is chiefly intended for
the use of japanners, cabinet-painters, coach-painters, &c.
_Best body copal varnish for coach-makers, &c._--This is intended for
the body parts of coaches and other similar vehicles, intended for
polishing.
Fuse 8 lbs. of fine African gum copal; add two gallons of clarified oil
(old measure); boil it very slowly for four or five hours, until quite
stringy; mix with three gallons and a half of turpentine; strain off,
and pour it into a cistern. As they are too slow in drying,
coach-makers, painters, and varnish-makers, have introduced to two pots
of the preceding varnish, one made as follows:--
8 lbs. of fine pale gum animé;
2 gallons of clarified oil;
3-1/2 gallons of turpentine.
To be boiled four hours.
_Quick drying body copal varnish, for coaches, &c._
(1.) 8 lbs. of the best African copal
2 gallons of clarified oil;
1/2 lb. of dried sugar of lead;
3-1/2 gallons of turpentine.
Boiled till stringy, and mixed and strained.
(2.) 8 lbs. of fine gum animé;
2 gallons of clarified oil;
1/4 lb. of white copperas;
3-1/2 gallons of turpentine.
Boiled as before.
To be mixed and strained while hot into the other pot. These two pots
mixed together will dry in six hours in winter, and in four in summer;
it is very useful for varnishing old work on dark colours, &c.
_Best pale carriage varnish._
(1.) 8 lbs. 2d sorted African copal;
2-1/2 gallons of clarified oil.
Boiled till very stringy.
1/4 lb. of dried copperas;
1/4 lb. of litharge;
5-1/2 gallons of turpentine.
Strained, &c.
(2.) 8 lbs. of 2d sorted gum animé;
2-1/2 gallons of clarified oil;
1/4 lb. of dried sugar of lead;
1/4 lb. of litharge;
5-1/2 gallons of turpentine.
Mix this to the first while hot.
This varnish will dry hard, if well boiled, in four hours in summer, and
in six in winter. As the name denotes, it is intended for the varnishing
of the wheels, springs, and carriage parts of coaches, chaises, &c.;
also, it is that description of varnish which is generally sold to and
used by house-painters, decorators, &c., as from its drying quality and
strong gloss, it suits their general purposes well.
_Second carriage varnish._
8 lbs. of 2d sorted gum animé;
2-3/4 gallons of fine clarified oil;
5-1/4 gallons of turpentine;
1/4 lb. of litharge;
1/4 lb. of dried sugar of lead;
1/4 lb. of dried copperas.
Boiled and mixed as before.
_Wainscot varnish._
8 lbs. of 2d sorted gum animé;
3 gallons of clarified oil;
1/4 lb. of litharge;
1/4 lb. of dried sugar of lead;
5-1/2 gallons of turpentine.
To be well boiled until it strings very strong, and then mixed
and strained.
Mahogany varnish is made either with the same proportions, with a little
darker gum; otherwise it is wainscot varnish, with a small portion of
gold size.
_Black japan_, is made by putting into the set-pot 48 pounds of Naples,
or any other of the foreign asphaltums (except the Egyptian). As soon as
it is melted, pour in 10 gallons of raw linseed oil; keep a moderate
fire, and fuse 8 pounds of dark gum animé in the gum-pot; mix it with 2
gallons of hot oil, and pour it into the set-pot. Afterwards fuse 10
pounds of dark or sea amber in the 10 gallon iron pot; keep stirring it
while fusing; and whenever it appears to be overheated, and rising too
high in the pot, lift it from the fire for a few minutes. When it
appears completely fused, mix in 2 gallons of hot oil, and pour the
mixture into the set-pot; continue the boiling for 3 hours longer, and
during that time introduce the same quantity of driers as before
directed: draw out the fire, and let it remain until morning; then boil
it until it rolls hard, as before directed: leave it to cool, and
afterwards mix with turpentine.
_Pale amber varnish._--Fuse 6 pounds of fine picked, very pale
transparent amber in the gum-pot, and pour in 2 gallons of hot clarified
oil. Boil it until it strings very strong. Mix with 4 gallons of
turpentine. This will be as fine as body copal, will work very free, and
flow well upon any work it is applied to: it becomes very hard, and is
the most durable of all varnishes; it is very excellent to mix in copal
varnishes, to give them a hard and durable quality. Observe; amber
varnish will always require a long time before it is ready for
polishing.
_Best Brunswick black._--In an iron pot, over a slow fire, boil 45
pounds of foreign asphaltum for at least 6 hours; and during the same
time boil in another iron pot 6 gallons of oil which has been previously
boiled. During the boiling of the 6 gallons, introduce 6 pounds of
litharge gradually, and boil until it feels stringy between the fingers;
then ladle or pour it into the pot containing the boiling asphaltum. Let
the mixture boil until, upon trial, it will roll into hard pills; then
let it cool, and mix it with 25 gallons of turpentine, or until it is of
a proper consistence.
_Iron-work black._--Put 48 pounds of foreign asphaltum into an iron pot,
and boil for 4 hours. During the first 2 hours, introduce 7 pounds of
red lead, 7 pounds of litharge, 3 pounds of dried copperas, and 10
gallons of boiled oil; add 1 eight-pound run of dark gum, with 2 gallons
of hot oil. After pouring the oil and gum, continue the boiling 2 hours,
or until it will roll into hard pills like japan. When cool, thin it off
with 30 gallons of turpentine, or until it is of a proper consistence.
This varnish is intended for blacking the iron-work of coaches and other
carriages, &c.
_A cheap Brunswick black._--Put 28 pounds of common black pitch, and 28
pounds of common asphaltum made from gas tar, into an iron pot; boil
both for 8 or 10 hours, which will evaporate the gas and moisture; let
it stand all night, and early next morning, as soon as it boils, put in
8 gallons of boiled oil; then introduce, gradually, 10 pounds of red
lead, and 10 pounds of litharge, and boil for 3 hours, or until it will
roll very hard. When ready for mixing, introduce 20 gallons of
turpentine, or more, until of a proper consistence. This is intended for
engineers, founders, ironmongers, &c.; it will dry in half an hour, or
less, if properly boiled.
_Axioms observed in the making of copal varnishes._--The more minutely
the gum is run, or fused, the greater the quantity, and the stronger the
produce. The more regular and longer the boiling of the oil and gum
together is continued, the more fluid or free the varnish will extend on
whatever it is applied to. When the mixture of oil and gum is too
suddenly brought to string by too strong a heat, the varnish requires
more than its just proportion of turpentine to thin it, whereby its oily
and gummy quality is reduced, which renders it less durable; neither
will it flow so well in laying on. The greater proportion of oil there
is used in varnishes, the less they are liable to crack, because the
tougher and softer they are. By increasing the proportion of gum in
varnishes, the thicker will be the stratum, the firmer they will set
solid, and the quicker they will dry. When varnishes are quite new made,
and must be sent out for use before they are of sufficient age, they
must always be left thicker than if they were to be kept the proper
time. Varnish made from African copal alone possesses the most
elasticity and transparency. Too much driers in varnish render it opaque
and unfit for delicate colours. Copperas does not combine with varnish,
but only hardens it. Sugar of lead does combine with varnish. Turpentine
improves by age; and varnish by being kept in a warm place. All copal or
oil varnishes require age before they are used.
_Concluding observations._--All body varnishes are intended and ought to
have 1-1/2 lbs. of gum to each gallon of varnish, when the varnish is
strained off, and cold; but as the _thinning up_, or quantity of
turpentine required to bring it to its proper consistence, depends very
much upon the degree of boiling the varnish has undergone, therefore,
when the gum and oil have not been strongly boiled, it requires less
turpentine for that purpose; whereas, when the gum and oil are very
strongly boiled together, a pot of 20 gallons will require perhaps 3
gallons above the regular proportionate quantity; and if mixing the
turpentine is commenced too soon, and the pot not sufficiently cool,
there will be frequently above a gallon and a half of turpentine lost by
evaporation.
All carriage, wainscot, and mahogany varnish ought to have fully 1 pound
of gum for each gallon, when strained and cold; and should one pot
require more than its proportion of turpentine, the following pot can
easily be left not quite so strongly boiled; then it will require less
turpentine to thin it up.
Gold sizes, whether pale or dark, ought to have fully half a pound of
good gum copal to each gallon, when it is finished; and the best black
japan, to have half a pound of good gum, or upwards, besides the
quantity of asphaltum.
_Fine mastic, or picture varnish._--Put 5 pounds of fine picked gum
mastic into a new 4-gallon tin bottle; get ready 2 pounds of glass,
bruised as small as barley; wash it several times; afterwards dry it
perfectly, and put it into the bottle with 2 gallons of turpentine that
has settled some time; put a piece of soft leather under the bung; lay
the tin on a sack upon the counter, table, or any thing that stands
solid; begin to agitate the tin, smartly rolling it backward and
forward, causing the gum, glass, and turpentine, to work as if in a
barrel-churn for at least 4 hours, when the varnish may be emptied out
into any thing sufficiently clean, and large enough to hold it. If the
gum is not all dissolved, return the whole into the bottle, and agitate
as before, until all the gum is dissolved; then strain it through fine
thin muslin into a clean tin bottle: leave it uncorked, so that the air
can get in, but no dust; let it stand for 9 months, at least, before it
is used; for the longer it is kept, the tougher it will be, and less
liable to chill or bloom. To prevent mastic varnish from chilling, boil
1 quart of river sand with 2 ounces of pearl-ashes; afterwards wash the
sand three or four times with hot water, straining it each time; put the
sand on a soup-plate to dry, in an oven; and when it is of a good heat,
pour half a pint of hot sand into each gallon of varnish, and shake it
well for 5 minutes; it will soon settle, and carry down the moisture of
the gum and turpentine, which is the general cause of mastic varnish
chilling on paintings.
_Common mastic varnish._--Put as much gum mastic, unpicked, into the
gum-pot as may be required, and to every 2-3/4 pounds of gum pour in 1
gallon of cold turpentine; set the pot over a very moderate fire, and
stir it with the stirrer; be careful, when the steam of the turpentine
rises near the mouth of the pot, to cover it with the carpet, and carry
it out of doors, as the vapour is very apt to catch fire. A few minutes’
low heat will perfectly dissolve 8 pounds of gum, which will, with 4
gallons of turpentine, produce, when strained, 4-1/2 gallons of varnish;
to which add, while yet hot, 5 pints of pale turpentine varnish, which
improves the body and hardness of the mastic varnish.
_Crystal varnish_, may be made either in the varnish-house,
drawing-room, or parlour. Procure a bottle of Canada balsam, which can
be had at any druggist’s; draw out the cork, and set the bottle of
balsam at a little distance from the fire, turning it round several
times, until the heat has thinned it; then have something that will hold
as much as double the quantity of balsam; carry the balsam from the
fire, and, while fluid, mix it with the same quantity of good
turpentine, and shake them together until they are well incorporated: in
a few days the varnish is fit for use, particularly if it is poured into
a half-gallon glass or stone bottle, and kept in a gentle warmth. This
varnish is used for maps, prints, charts, drawings, paper ornaments,
&c.; and when made upon a larger scale, requires only warming the balsam
to mix with the turpentine.
_White hard spirit-of-wine varnish._--Put 5 pounds of gum sandarac into
a 4-gallon tin bottle, with 2 gallons of spirits of wine, 60 over proof,
and agitate it until dissolved, exactly as directed for the best mastic
varnish, recollecting, if washed glass is used, that it is convenient to
dip the bottle containing the gum and spirits into a copperful of hot
water every 10 minutes--the bottle to be immersed only 2 minutes at a
time--which will greatly assist the dissolving of the gum; but, above
all, be careful to keep a firm hold over the cork of the bottle,
otherwise the rarefaction will drive the cork out with the force of a
shot, and perhaps set fire to the place. The bottle, every time it is
heated, ought to be carried away from the fire; the cork should be eased
a little, to allow the rarefied air to escape; then driven tight, and
the agitation continued in this manner until all the gum is properly
dissolved; which is easily known by having an empty tin can to pour the
varnish into, until near the last, which is to be poured into a gallon
measure. If the gum is not all dissolved, return the whole into the
4-gallon tin, and continue the agitation until it is ready to be
strained, when every thing ought to be quite ready, and perfectly clean
and dry, as oily tins, funnels, strainers, or any thing damp, or even
cold weather, will chill and spoil the varnish. After it is strained
off, put into the varnish 1 quart of very pale turpentine varnish, and
shake and mix the two well together. Spirit varnishes should be kept
well corked: they are fit to use the day after being made.
_Brown hard spirit varnish_--is made by putting into a bottle 3 pounds
of gum sandarac, with 2 pounds of shellac, and 2 gallons of spirits of
wine, 60 over proof; proceeding exactly as before directed for the white
hard varnish, and agitating it when cold, which requires about 4 hours’
time, without any danger of fire; whereas, making any spirit varnish by
heat is always attended with danger. No spirit varnish ought to be made
either near a fire or by candle light. When this brown hard is strained,
add 1 quart of turpentine varnish, and shake and mix it well: next day
it is fit for use.
The _Chinese varnish_, comes from a tree, which grows in Cochin-China,
China, and Siam. It forms the best of all varnishes.
_Gold lacker._--Put into a clean 4-gallon tin, 1 pound of ground
turmeric, 1-1/2 ounces of powdered gamboge, 3-1/2 pounds of powdered gum
sandarac, 3/4 of a pound of shellac, and 2 gallons of spirits of wine.
After being agitated, dissolved, and strained, add 1 pint of turpentine
varnish, well mixed.
_Red spirit lacker._
2 gallons of spirits of wine;
1 pound of dragon’s blood;
3 pounds of Spanish annotto;
3-1/4 pounds of gum sandarac;
2 pints of turpentine.
Made exactly as the yellow gold lacker.
_Pale brass lacker._
2 gallons of spirits of wine;
3 ounces of Cape aloes, cut small;
1 pound of fine pale shellac;
1 ounce gamboge, cut small.
No turpentine varnish. Made exactly as before.
But observe, that those who make lackers, frequently want some paler,
and some darker, and sometimes inclining more to the particular tint of
certain of the component ingredients. Therefore, if a 4-ounce phial of a
strong solution of each ingredient be prepared, a lacker of any tint can
be produced at any time.
_Preparation of linseed oil for making varnishes._--Put 25 gallons of
linseed oil into an iron or copper pot that will hold at least 30
gallons; put a fire under, and gradually increase the heat, so that the
oil may only simmer, for 2 hours; during that time the greatest part of
its moisture evaporates; if any scum arises on the surface, skim it off,
and put that aside for inferior purposes. Then increase the gradually,
and sprinkle in, by a little at a time, 3 lbs. of scale litharge, 3 lbs.
of good red lead, and 2 lbs. of Turkey umber, all well dried and free
from moisture. If any moist driers are added, they will cause the oil to
tumefy; and, at the same time, darken it, causing it to look opaque and
thick, ropy and clammy, and hindering it from drying and hardening in
proper time; besides, it will lie on the working painting like a piece
of bladder skin, and be very apt to rise in blisters. As soon as all the
driers are added to the oil, keep quietly stirring the driers from the
bottom of the pot; otherwise they will burn, which will cause the oil to
blacken and thicken before it is boiled enough. Let the fire be so
regulated that the oil shall only boil slowly for three hours from the
time all the driers were added; if it then ceases to throw up any scum,
and emits little or no smoke, it is necessary to test its temperature by
a few quill tops or feathers. Dip a quill top in the oil every two
minutes, for when the oil is boiled enough, the quill top will crackle
or curl up quite burnt; if so, draw out the fire immediately, and let
the oil remain in the pot at least from 10 to 24 hours, or longer if
convenient, for the driers settle much sooner when the oil is left to
cool in the pot, than when it is immediately taken out.
_Poppy oil._--Into four pints of pure soft water, put two ounces of
foreign white vitriol; warm the water in a clean copper pan, or glazed
earthen jar, until the vitriol is dissolved; pour the mixture into a
clean glass or stone bottle, large enough to contain three gallons; then
add to the solution of vitriol one gallon and a half of poppy oil, cork
and agitate the bottle regularly and smartly for at least two hours;
then pour out the contents into a wide earthenware dish: leave it at
rest for eight days, when the oil will be clean and brilliant on the
surface, and may be taken off with a spoon or flat skimmer, and put up
in a glass bottle and exposed to the light, which in a few weeks renders
the oil exceedingly limpid and colourless.
_Nut-oil, or oil of walnuts_, is extracted by expression; and that which
is extracted without heat, is certainly the most pale, pure, and
nutritive seasoning, and retains an exquisite taste of the fruit. That
designed for the arts is of inferior quality, and is plentifully
imported to us from France; the heat it undergoes in its torrefaction,
previous to its expression, disposes it to dry more quickly than that
expressed by the cold process; but, at the same time, the heat, though
it frees it from its unctuous quality, gives it more colour. When it has
been extracted by the cold process, it may be prepared in the same way
as directed for the poppy oil.
In the above article I have retained the workmen’s names--gum, white
vitriol, &c., instead of resin, sulphate of zinc, &c.
VEINS (_Filons_, Fr.; _Gänge_, Germ.); are the fissures or rents in
rocks, which are filled with peculiar mineral substances, most commonly
metallic ores.
VEIN STONES, or GANGUES, are the mineral substances which accompany, and
frequently enclose, the metallic ores.
VELLUM, is a fine sort of PARCHMENT, which see.
VELVET (_Velours_, Fr.; _Sammet_, Germ.); a peculiar stuff, the nature
of which is explained under FUSTIAN and TEXTILE FABRICS.
VENETIAN CHALK, is STEATITE.
VENUS, is the mythological name of copper.
VENTILATION, or the renewal of fresh air in stagnant places, is nowhere
exhibited to such advantage as in the coal mines of Northumberland and
Durham, where Mr. Buddle has carried well nigh to systematic perfection
the plan of coursing the air through the winding galleries, originally
contrived about the year 1760, by Mr. James Spedding, of Workington, the
ablest pitman of his day.[69] He converted the whole of the passages
into air-pipes, so to speak, drew the current of air from the downcast
pit, then traversed it up and down, and round about, through the several
sheths of the workings, so that no particular gallery was left without a
current of air. He thereby succeeded in actually expelling the noxious
gases from the mines; those demons, which in Germany, at no remote era,
were wont to be combated by the priests with impotent exorcisms or pious
frauds. Before Mr. Buddle introduced his improvements, he has known the
air to be led through a series of workings, thirty miles long, before it
made its exit. There is in every coal mine an experienced corps, called
wastemen, because they travel over the waste, or the exhausted regions,
who can tell at once, by the whistling sound which the air makes at the
crevices in certain partitions and doors, whether the ventilation be in
good condition or not. They hear these stoppings begin to _sing_ or
_call_, as they say, whenever an interruption takes place in any point
of the labyrinthian line. Another indication of something being wrong,
is when the doors get so heavy, that the boys in attendance upon them
find them difficult to shut or open. The instant such a defect is
discovered by any one, he cries aloud, “Holloa, there is something
wrong--the doors are calling!”
[69] Mining engineers use the term _good pitman_, as admirals do _good
seaman_, to denote a proficient in his calling.
In Mr. Spedding’s system, the whole of the return air came in one
current to his rarefying furnace (see letter C, _fig._ 1158.), whether
it was at the explosive point or not. This distribution was often
fraught with such danger, that a torrent of water had to be kept in
readiness, under the name of the waterfall, to be let down to extinguish
the fire in a moment. Many explosions at that time occurred, from the
furnaces below, and also down through tubes from the furnaces
above-ground.
[Illustration: 1158]
About the year 1807, Mr. Buddle had his attention intensely occupied
with this most important object, and then devised his plan of a divided
current, carrying that portion through the active furnace C, _fig._
1158., and the portion of the air from the _foul_ workings of the air
which, descending in the downcast pit A, coursed through the _clean_
workings, up the dumb furnace D, till it reached a certain elevation in
B, the upcast pit, above the fireplace. The pitmen had a great aversion,
however, at first, to adopt this plan, as they thought that the current
of air, by being split, would lose its ventilating power; but they were,
ere long, convinced by Mr. Buddle to the contrary. He divides the main
current into two separate streams, at the bottom of the pit A, as shown
by darts in the figure; the feathered ones, representing that part of
the pit in which the course of the current of air is free from explosive
mixture, or does not contain above one-thirtieth of carburetted
hydrogen, as indicated by its effect upon the flame of a candle. The
naked darts denote the portions of the mine where the air, being charged
to the firing point, is led off towards D, the dumb furnace, which
communicates with the hot upcast shaft, out of reach of the flame, and
thence derives its power of draught. By suitable alterations in the
stoppings (see the various transverse lines, and the crosses), any
portion of the workings may, by the agency of the furnace, be laid out
of, or brought within, the course of the vitiated current, at the
pleasure of the skilful mine-viewer; so that, if he found it necessary,
he could confine, by proper arrangements of his furnace, all the
vitiated current to a mere gas-pipe or drift, and direct it wholly
through the dumb furnace. During a practice of twenty years, Mr. Buddle
has not met with any accident in consequence of a defect in the
stoppings preventing the complete division of the air. The engineer has
it thus within his power to detach or insulate those portions of the
mine in which there is a great exudation of gas, from the rest; and,
indeed, he is continually making changes, borrowing and lending
currents, so to speak; sometimes laying one division or panel upon the
one air-course, and sometimes upon the other, just to suit the immediate
emergency. As soon as any district has ceased to be dangerous, by the
exhaustion of the gas-blowers, it is transferred from the foul to the
pure air course, where gunpowder may be safely used, as also candles,
instead of Davy’s lamps, which give less light.
The quantity of air put down into the Wallsend colliery, at the time of
the last dreadful accident, 18th June, 1835, was not less than 5000
cubic feet per minute, whence it has been justly inferred that the
explosion was caused by the rashness of a wasteman carrying a light
through a door into a foul drift.
Till the cutting out of the pillars commences (see the right end of the
diagram), the ventilation of the several passages, boards, &c., may be
kept perfect, supposing the working extended no further than _a_, or
_b_; because, as long as there are pillars standing, every passage may
be converted into an air-conduit, for leading a current of air in any
direction, either to C, the burning, or D, the dumb furnace. But the
first pillar that is removed deranges the ventilation at that spot, and
takes away the means of carrying the air into the further recess towards
_c_. In taking out the pillars, the miners always work to windward, that
is to say, against the stream of air; so that, whatever gas may be
evolved, shall be immediately carried off from the people at work. When
a range of pillars has been removed, as at _d_, _e_, _f_, no power
remains of dislodging the gas from the section of the mine beyond _a_,
_b_; and as the pillars are successively cut away to the left hand of
the line _a_, _b_, the size of the _goaf_, or void, is increased. This
vacuity is a true gas-holder, or reservoir, continually discharging
itself at the points _g_, _h_, _i_, into the circulating current, to be
carried off by the gas-pipe drift at the dumb furnace, but not to be
suffered ever to come in contact with flame of any description. The next
range of working, is the line of pillars to the left of _a_, _b_; the
coal having been entirely cleared out of the space to the right, where
the place of the pillars is marked by dotted lines. The roof in the
waste soon falls down, and gets fractured up to the next seam of coal,
called the yard-coal seam, which, abounding in gas, sends it down in
large quantities, and keeps the immense gasometer, or goaf below,
continually replenished. See STOVE.
VERATRINE, is a vegetable alkali, of a poisonous nature, extracted from
the seeds of the _Veratrum sabadilla_, the roots of the _Veratrum
album_, or white hellebore, and of _Colchicum autumnale_, or meadow
saffron, in which plants it exists combined chiefly with gallic acid. It
is obtained in the form of a white powder. It has an acrid, burning
taste, but without any bitterness; it has no smell; but when snuffed
into the nostrils, it excites violent and dangerous sneezing. It melts
at a heat of 122° F., and concretes, on cooling, into a transparent
yellowish mass. It restores the blue colour of reddened litmus paper. It
is hardly soluble in water or ether, but abundantly in alcohol. It
consists of--carbon 66·75, hydrogen 8·54, nitrogen 5·04, and oxygen
19·60. Its saline compounds have an acrid and burning taste. Veratrine
resembles strychnine and brucine, in its effects upon living bodies,
producing tetanus and death in a moderate dose; notwithstanding which,
it has been prescribed by some of our poison doctors, especially mixed
with hog’s lard, in the form of frictions on the forehead, for nervous
maladies; but seldom, I believe, with any good effects.
VERDIGRIS. (_Vert-de-gris_, Fr.; _Grünspan_, Germ.) The copper used in
this manufacture, is formed into round sheets, from 20 to 25 inches
diameter, by one twenty-fourth of an inch in thickness. Each sheet is
then divided into oblong squares, from 4 to 6 inches in length, by 3
broad; and weighing about 4 ounces. They are separately beaten upon an
anvil, to smooth their surfaces, to consolidate the metal, and to free
it from scales. The refuse of the grapes, after the extraction of their
juice, formerly thrown on to the dunghill, is now preserved for the
purpose of making verdigris. It is put loosely into earthen vessels,
which are usually 16 inches high, 14 in diameter at the widest part, and
about 12 at the mouth. The vessels are then covered with lids, which are
surrounded by straw mats. In this situation the materials soon become
heated, and exhale an acid odour; the fermentation beginning at the
bottom of the cask, and gradually rising till it actuate the whole mass.
At the end of two or three days, the manufacturer removes the fermenting
materials into other vessels, in order to check the process, lest
putrefaction should ensue. The copper plates, if new, are now prepared,
by rubbing them over with a linen cloth dipt in a solution of verdigris;
and they are laid up alongside of one another to dry. If the plates are
not subjected to this kind of preparation, they will become black,
instead of green, by the first operation. When the plates are ready, and
the materials in a fermenting state, one of them is put into the
earthern vessel for 24 hours, in order to ascertain whether it be a
proper period to proceed to the remaining part of the process. If, at
the end of this period, the plate be covered with an uniform green
layer, concealing the whole copper, every thing is right; but if, on the
contrary, liquid drops hang on the surface of the metal, the workmen say
the plates are _sweating_, and conclude that the heat of the fermented
mass has been inadequate; on which account another day is allowed to
pass before making a similar trial. When the materials are finally found
to be ready, the strata are formed in the following manner. The plates
are laid on a horizontal wooden grating, fixed in the middle of a vat,
on whose bottom a pan full of burning charcoal is placed, which heats
them to such a degree, that the women who manage this work are obliged
to lay hold of them frequently with a cloth when they lift them out.
They are in this state put into earthern vessels, in alternate strata
with the fermented materials, the uppermost and undermost layers being
composed of the expressed grapes. The vessels are covered with their
straw mats, and left at rest. From 30 to 40 pounds of copper are put
into one vessel.
At the end of 10, 12, 15, or 20 days the vessels are opened, to
ascertain, by the materials having become white, if the operation be
completed.
Detached glossy crystals will be perceived on the surface of the plates;
in which case the grapes are thrown away, and the plates are placed
upright in a corner of the verdigris cellar, one against the other, upon
pieces of wood laid on the ground. At the end of two or three days they
are moistened by dipping in a vessel of water, after which they are
replaced in their former situation, where they remain seven or eight
days, and are then subjected to momentary immersion, as before. This
alternate moistening and exposure to air is performed six or eight
times, at regular intervals of about a week. As these plates are
sometimes dipped into damaged wine, the workmen term these immersions,
_one wine_, _two wines_, &c.
By this treatment, the plates swell, become green, and covered with a
stratum of verdigris, which is readily scraped off with a knife. At each
operation every vessel yields from five to six pounds of verdigris, in a
_fresh_ or _humid_ state; which is sold to wholesale dealers, who dry it
for exportation. For this purpose, they knead the paste in wooden
troughs, and then transfer it to leathern bags, a foot and a half long,
and ten inches in diameter. These bags are exposed to the sun and air
till the verdigris has attained a sufficient degree of hardness. It
loses about half its weight in this operation; and it is said to be
knife-proof, when this instrument, plunged through the leathern bag,
cannot penetrate the loaf of verdigris.
The manufacture of verdigris at Montpellier is altogether domestic. In
most wine farm-houses there is a verdigris cellar; and its principal
operations are conducted by the females of the family. They consider the
forming the strata, and scraping off the verdigris, the most troublesome
part. Chaptal says that this mode of making verdigris would admit of
some improvements: for example, the acetification requires a warmer
temperature than what usually arises in the earthen vessels; and the
plates, when set aside to generate the coat of verdigris, require a
different degree of heat and moisture from that requisite for the other
operations.
Verdigris is a mixture of the crystallized acetate of copper and the
sub-acetate, in varying proportions. According to Vauquelin’s
researches, there are three compounds of oxide of copper and acetic
acid; 1. a subacetate, insoluble in water, but decomposing in that
fluid, at common temperatures changing into peroxide and acetate; 2. a
neutral acetate, the solution of which is not altered at common
temperatures, but is decomposed by ebullition, becoming peroxide and
superacetate; and, 3. superacetate, which in solution is not
decomposed, either at common temperatures or at the boiling point; and
which cannot be obtained in crystals, except by slow spontaneous
evaporation, in air or _in vacuo_. The first salt, in the dry state,
contains 66·51 of oxide; the second, 44·44; and the third, 33·34.
Mr. Phillips has given the following analyses of French and English
verdigris; _Annals of Philosophy_, No. 21.--
French English
Verdigris. Verdigris.
Acetic acid 29·3 29·62
Peroxide of copper 43·5 44·25
Water 25·2 25·51
Impurity 2·0 0·62
----- ------
100·0 100·00
_Distilled verdigris_, as it was long erroneously called, is merely a
_binacetate_ or superacetate of copper, made by dissolving, in a copper
kettle, one part of verdigris in two of distilled vinegar; aiding the
mutual action by slight heat and agitation with a wooden spatula. When
the liquor has taken its utmost depth of colour, it is allowed to
settle, and the clear portion is decanted off into well glazed earthen
vessels. Fresh vinegar is poured on the residuum, and if its colour does
not become deep enough, more verdigris is added. The clear and saturated
solution is then slowly evaporated, in a vessel kept uniformly filled,
till it acquires the consistence of syrup, and shows a pellicle on its
surface; when it is transferred into glazed earthen pans, called _oulas_
in the country. In each of these dishes, two or three sticks are placed,
about a foot long, cleft till within two inches of their upper end, and
having the base of the cleft kept asunder by a bit of wood. This kind of
pyramid is suspended by its summit in the liquid. All these vessels are
transported into crystallizing rooms, moderately heated with a stove,
and left in the same state for 15 days, taking care to maintain an
uniform temperature. Thus are obtained very fine groups of crystals of
acetate of copper, clustered round the wooden rods; on which they are
dried, taken off, and sent into the market. They are distinctly
rhomboidal in form, and of a lively deep blue colour. Each cluster of
crystals weighs from five to six pounds; and, in general, their total
weight is equal to about one-third of the verdigris employed.
The crystallized binacetate of commerce consists, by my analysis,
of--acetic acid, 52; oxide of copper, 39·6; water, 8·4, in 100. I have
prepared crystals which contain no water. There is a triple acetate of
copper and lime, which resembles distilled verdigris in colour. It was
manufactured pretty extensively in Scotland some years ago, and fetched
a high price, till I published an analysis of it in the Edinburgh
Philosophical Journal. It is much inferior, for all uses in the arts, to
the proper binacetate.
VERDITER, or BLUE VERDITER. This is a precipitate of oxide of copper
with lime, made by adding that earth, in its purest state, to the
solution of nitrate of copper, obtained in quantities by the refiners,
in parting gold and silver from copper by nitric acid. The cupreous
precipitate must be triturated with lime, after it is nearly dry, to
bring out the fine velvety blue colour. The process is delicate, and
readily misgives in unskilful hands.
The _cendres bleues en pâte_ of the French, though analogous, are in
some respects a different preparation. To make it, dissolve sulphate of
copper in hot water, in such proportions that the liquid may have a
density of 1·3. Take 240 pound measures of this solution, and divide it
equally into 4 open-headed casks; add to each of these 45 pound measures
of a boiling-hot solution of muriate of lime, of specific gravity 1·317,
whereby a double decomposition will ensue; with the formation of muriate
of copper and sulphate of lime, which precipitates. It is of consequence
to work the materials well together at the moment of mixture, to prevent
the precipitate agglomerating in unequal masses. After leaving it to
settle for 12 hours, a small quantity of the clear liquor may be
examined, to see whether the just proportions of the two salts have been
employed, which is done by adding either sulphate of copper or muriate
of lime. Should either cause much precipitation, some of the other must
be poured in till the equivalent decomposition be accomplished; though
less harm results from an excess of sulphate of copper than of muriate
of lime.
The muriate of copper is to be decanted from the subsided gypsum, which
must be drained and washed in a filter; and these blue liquors are to be
added to the stronger; and the whole distributed, as before, into 4
casks; composing in all 670 pound measures of a green liquor, of 1·151
specific gravity.
Meanwhile, a magma of lime is to be prepared as follows:--100 pounds of
quicklime are to be mixed up with 300 pounds of water, and the mixture
is to be passed through a wire-gauze sieve, to separate the stony and
sandy particles, and then to be ground in a proper mill to an impalpable
paste. About 70 or 80 pounds of this mixture (the beauty of the colour
is inversely as the quantity of lime) are to be distributed in equal
portions between the four casks, strongly stirring all the time with a
wooden spatula. It is then left to settle, and the limpid liquor is
tested by ammonia, which ought to occasion only a faint blue tinge; but
if the colour be deep blue, more of the lime paste must be added. The
precipitate is now to be washed by decantation, employing for this
purpose the weak washings of a former operation; and it is lastly to be
drained and washed on a cloth filter. The proportions of material
prescribed above, furnish from 500 to 540 pounds of green paste.
Before making further use of this paste, the quantity of water present
in it must be determined by drying 100 or 200 grains. If it contain 27
per cent. of dry matter, 12 pounds of it may be put into a wooden bucket
(and more or less in the ratio of 12 to to 27 per cent.) capable of
containing 17-1/2 pints; a pound (measure) of the lime paste is then to
be rapidly mixed into it; immediately afterwards, a pint and a quarter
of a watery solution of the pearlash of commerce, of spec. grav. 1·114,
previously prepared; and the whole mixture is to be well stirred, and
immediately transferred to a colour-mill. The quicker this is done, the
more beautiful is the shade.
On the other hand, two solutions must have been previously made ready,
one of sal-ammoniac (4 oz. troy dissolved in 3-1/2 pints of water), and
another of sulphate of copper (8 oz. troy dissolved in 3-1/2 pints of
water).
When the paste has come entirely through the mill, it is to be quickly
put into a jar, and the two preceding solutions are to be simultaneously
poured into it; when a cork is to be inserted, and the jar is to be
powerfully agitated. The cork must now be secured with a fat lute. At
the end of four days this jar and three of its fellows are to be emptied
into a large hogshead nearly full of clear water, and stirred well with
a paddle. After repose, the supernatant liquid is run off; when it is
filled up again with water, and elutriated several times in succession,
till the liquid no longer tinges turmeric paper brown. The deposit may
be then drained on a cloth filter. The pigment is sold in the state of a
paste; and is used for painting, or printing paper-hangings for the
walls of apartments.
The above prescribed proportions furnish the superfine blue paste: for
the second quality, one-half more quicklime paste is used; and for the
third, double of the lime and sal ammoniac; but the mode of preparation
is in every case the same.
This paste may be dried into a blue powder, or into crayons for
painters, by exposing it on white deals to a very gentle heat in a shady
place. This is called _cendres bleues en pierre_.
VERDITER, or BREMEN GREEN. This pigment is a light powder, like
magnesia, having a blue or bluish green colour. The first is most
esteemed. When worked up with oil or glue, it resists the air very well;
but when touched with lime, it is easily affected, provided it has not
been long and carefully dried. A strong heat deprives it of its lustre,
and gives it a brown or blackish-green tint.
The following is, according to M. J. G. Gentele, the process of
fabrication in Bremen, Cassel, Eisenach, Minden, &c.:--
_a._ 225 lbs. of sea salt, and 222 lbs. of blue vitriol, both free from
iron, are mixed in the dry state, then reduced between mill-stones with
water to a thick homogeneous paste.
_b._ 225 lbs. of plates of old copper are cut by scissors into bits of
an inch square, then thrown and agitated in a wooden tub containing two
lbs. of sulphuric acid, diluted with a sufficient quantity of water, for
the purpose of separating the impurities; they are afterwards washed
with pure water in casks made to revolve upon their axes.
_c._ The bits of copper being placed in oxidation-chests, along with the
magma of common salt and blue vitriol previously prepared in strata of
half an inch thick, they are left for some time to their mutual
reaction. The above chests are made of oaken planks joined without iron
nails, and set aside in a cellar, or other place of moderate
temperature.
The saline mixture, which is partially converted into sulphate of soda
and chloride of copper, absorbs oxygen from the air, whereby the
metallic copper passes into a hydrated oxide, with a rapidity
proportioned to the extent of the surfaces exposed to the atmosphere. In
order to increase this exposure, during the three months that the
process requires, the whole mass must be turned over once every week,
with a copper shovel, transferring it into an empty chest alongside, and
then back into the former one.
At the end of three months, the corroded copper scales must be picked
out, and the saline particles separated from the slimy oxide with the
help of as little water as possible.
_d._ This oxidized _schlam_, or mud, is filtered, then thrown, by means
of a bucket containing 30 pounds, into a tub, where it is carefully
divided or comminuted.
_e._ For every six pailfuls of _schlam_ thus thrown into the large tub,
12 pounds of muriatic acid, at 15° Baumé, are to be added; the mixture
is to be stirred, and then left at rest for 24 or 36 hours.
_f._ Into another tub, called the blue back, there is to be introduced,
in like manner, for every six pailfuls of the acidified _schlam_, 15
similar pailfuls of a solution of colourless clear caustic alkali, at
19° Baumé.
_g._ When the back (_e_) has remained long enough at rest, there is to
be poured into it a pail of pure water for every pail of _schlam_.
_h._ When all is thus prepared, the set of workmen who are to empty the
back (_e_), and those who are to stir (_f_), must be placed alongside of
each. The first set transfer the _schlam_ rapidly into the latter back;
where the second set mix and agitate it all the time requisite to
convert the mass into a consistent state, and then leave it at rest from
36 to 48 hours.
The whole mass is to be now washed; with which view it is to be stirred
about with the affusion of water, allowed to settle, and the supernatant
liquor is drawn off. This process is to be repeated till no more traces
of potash remain among the blue. The deposit must be then thrown upon a
filter, where it is to be kept moist, and exposed freely to the air. The
pigment is now squeezed in the filter-bags, cut into bits, and dried in
the atmosphere, or at a temperature not exceeding 78° Fahr. It is only
after the most complete desiccation that the colour acquires its
greatest lustre.
VERMICELLI, is a paste of wheat flour, drawn out and dried in slender
cylinders, more or less tortuous, like worms, whence the Italian name.
The _gruau_ of the French is wheat coarsely ground, so as to free it
from the husk; the hardest and whitest part, being separated by sifting,
is preferred for making the finest bread. When this _gruau_ is a little
more ground, and the dust separated from it by the boulting-machine, the
granular substance called _semoule_ is obtained, which is the basic of
the best pastes. The softest and purest water is said to be necessary
for making the most plastic vermicelli dough; 12 pounds of it being
usually added to 50 pounds of _semoule_. It is better to add more
_semoule_ to the water, than water to the _semoule_, in the act of
kneading. The water should be hot, and the dough briskly worked while
still warm. The Italians pile one piece of this dough upon another, and
then tread it well with their feet for two or three minutes. They
afterwards work it for two hours with a powerful rolling-pin, a bar of
wood from 10 to 12 feet long, larger at the one end than the other,
having a sharp cutting edge at the extremity, attached to the large
kneading-trough.
When the dough is properly prepared, it is reduced to thin ribands,
cylinders, or tubes, to form vermicelli and macaroni of different kinds.
This operation is performed by means of a powerful press. This is
vertical, and the iron plate or follower carried by the end of the screw
fits exactly into a cast-iron cylinder, called the _bell_, like a
sausage-machine, of which the bottom is perforated with small holes, of
the shape and size intended for the vermicelli. The _bell_ being filled,
and warmed with a charcoal fire to thin the dough into a paste, this is
forced slowly through the holes, and is immediately cooled and dried by
a fanner as it protrudes. When the threads or fillets have acquired the
length of a foot, they are grasped by the hand, broken off, and twisted,
while still flexible, into any desired shape upon a piece of paper.
The macaroni requires to be made of a less compact dough than the
vermicelli. The former is forced through the perforated bottom, usually
in fillets, which are afterwards formed into tubes by joining their
edges together before they have had time to become dry. The _lazagnes_
are macaroni left in the fillet or riband shape.
VERMILLION, or _Cinnabar_, is a compound of mercury and sulphur in the
proportion of 100 parts of the former to 16 of the latter, which occurs
in nature as a common ore of quicksilver, and is prepared by the chemist
as a pigment, under the name of Vermillion. It is, properly speaking, a
bisulphuret of mercury. This artificial compound being extensively
employed, on account of the beauty of its colour, in painting, for
making red sealing-wax, and other purposes, is the object of an
important manufacture. When vermillion is prepared by means of
sublimation, it concretes in masses of considerable thickness, concave
on one side, convex on the other, of a needle-form texture; brownish-red
in the lump, but when reduced to powder of a lively red colour. On
exposure to a moderate heat, it evaporates without leaving a residuum,
if it be not contaminated with red lead; and at a higher heat, it takes
fire, and burns entirely away, with a blue flame.
Holland long kept a monopoly of the manufacture of vermillion, from
being alone in possession of the art of giving it a fine flame colour.
Meanwhile the French chemists examined this product with great care,
under an idea that the failure of other nations to rival the Dutch,
arose from ignorance of its true composition; some, with Berthollet,
imagined that it contained a little hydrogen; and others, with Fourcroy,
believed that the mercury contained in it was oxidized; but, eventually,
Seguin proved that both of these opinions were erroneous; having
ascertained, on the one hand, that no hydrogenous matter was given out
in the decomposition of cinnabar, and on the other that sulphur and
mercury, by combining, were transformed into the red sulphuret in close
vessels, without the access of any oxygen whatever. It was likewise
supposed that the solution of the problem might be found in the
difference of composition between the red and black sulphurets of
mercury; and many conjectures were made with this view, the whole of
which were refuted by Seguin. He demonstrated, in fact, that a mere
change of temperature was sufficient to convert the one sulphuret into
the other, without occasioning any variation in the proportion of the
two elements. Cinnabar, moderately heated in a glass tube, is
convertible into ethiops, which in its turn is changed into cinnabar by
exposing the tube to a higher temperature; and thence he was led to
conclude that the difference between these two sulphurets was owing
principally to the state of the combination of the constituents. It
would seem to result, from all these researches, that cinnabar is only
an intimate compound of pure sulphur and mercury, in the proportions
pointed out by analysis; and it is therefore reasonable to conclude,
that in order to make fine vermillion, it should be sufficient to effect
the union of its elements at a high enough temperature, and to exclude
the influence of all foreign matters; but, notwithstanding these
discoveries, the art of making good vermillion is nearly as much a
mystery as ever. M. Seguin, indeed, announced in his Memoirs, that he
had succeeded in obtaining, in his laboratory, as good a cinnabar as
that of Holland, and at a remunerative price; but whatever truth may be
in this assertion, or however much the author may have been excited by
the love of honour and profit, no manufacture on the great scale sprung
up under his auspices. France is still as tributary as ever to foreign
nations for this chemical product. At an exposition some years ago,
indeed, a sample of good French vermillion was brought forward to prove
that the problem was nearly solved; but that it is not so completely,
may be inferred from the silence on this subject in M. Dupin’s report of
the last exposition, in 1834, where we see so many chemical trifles
honoured with eulogiums and medals by the judges of the show. The
English vermillion is now most highly prized by the French manufacturers
of sealing-wax.
M. Tuckert, apothecary of the Dutch court, published, long ago, in the
_Annales de Chimie_, vol. iv., the best account we yet have of the
manufacture of vermillion in Holland; one which has been since verified
by M. Payssé, who saw the process practised on the great scale with
success.
“The establishment in which I saw, several times, the fabrication of
sublimed sulphuret of mercury,” says M. Tuckert, “was that of Mr. Brand,
at Amsterdam, beyond the gate of Utrecht; it is one of the most
considerable in Holland, producing annually, from three furnaces, by
means of four workmen, 48,000 pounds of cinnabar, besides other
mercurial preparations. The following process is pursued here:--
“The ethiops is first prepared by mixing together 150 pounds of sulphur,
with 1080 pounds of pure mercury, and exposing this mixture to a
moderate heat in a flat polished iron pot, one foot deep, and two feet
and a half in diameter. It never takes fire, provided the workman
understands his business. The black sulphuret, thus prepared, is ground,
to facilitate the filling with it of small earthen bottles capable of
holding about 24 ounces of water; from 30 to 40 of which bottles are
filled beforehand, to be ready when wanted.
“Three great subliming pots or vessels, made of very pure clay and sand,
have been previously coated over with a proper lute, and allowed to dry
slowly. These pots are set upon three furnaces bound with iron hoops,
and they are covered with a kind of iron dome. The furnaces are
constructed so that the flame may freely circulate and play upon the
pots, over two-thirds of their height.
“The subliming vessels having been set in their places, a moderate fire
is kindled in the evening, which is gradually augmented till the pots
become red. A bottle of the black sulphuret is then poured into the
first in the series, next into the second and third, in succession; but
eventually, two, three, or even more, bottles may be emptied in at once;
this circumstance depends on the stronger or weaker combustion of the
sulphuret of mercury thus projected. After its introduction, the flame
rises 4 and sometimes 6 feet high; when it has diminished a little, the
vessels are covered with a plate of iron, a foot square, and an inch and
a half thick, made to fit perfectly close. In this manner, the whole
materials which have been prepared are introduced, in the course of 34
hours, into the three pots; being for each pot, 360 pounds of mercury,
and 50 of sulphur; in all, 410 pounds.”
The degree of firing is judged of, from time to time, by lifting off the
cover; for if the flame rise several feet above the mouth of the pot,
the heat is too great; if it be hardly visible, the heat is too low. The
proper criterion being a vigorous flame playing a few inches above the
vessel. In the last of the 36 hours’ process, the mass should be
dexterously stirred up every 15 or 20 minutes, to quicken the
sublimation. The subliming pots are then allowed to cool, and broken to
pieces in order to collect all the vermillion encrusted within them;
and which usually amounts to 400 lbs., being a loss of only 60 on each
vessel. The lumps are to be ground along with water between horizontal
stones, elutriated, passed through sieves, and dried. It is said that
the rich tone of the Chinese vermillion may be imitated by adding to the
materials for subliming one per cent. of sulphuret of antimony, and by
digesting the ground article first in a solution of sulphuret of
potassa, and, finally, in diluted muriatic acid.
The humid process of Kirchoff has of late years been so much improved,
as to furnish a vermillion quite equal in brilliancy to the Chinese. The
following process has been recommended. Mercury is triturated for
several hours with sulphur, in the cold, till a perfect ethiops is
formed; potash lye is then added, and the trituration is continued for
some time. The mixture is now heated in iron vessels, with constant
stirring at first, but afterwards only from time to time. The
temperature must be kept up as steadily as possible at 130° Fahr.,
adding fresh supplies of water as it evaporates. When the mixture which
was black, becomes, at the end of some hours, brown-red, the greatest
caution is requisite, to prevent the temperature from being raised above
114°, and to preserve the mixture quite liquid, while the compound of
sulphur and mercury should always be pulverulent. The colour becomes
red, and brightens in its hue, often with surprising rapidity. When the
tint is nearly fine, the process should be continued at a gentler heat,
during some hours. Finally, the vermillion is to be elutriated, in order
to separate any particles of running mercury. The three ingredients
should be very pure. The proportion of product varies with that of the
constituents, as we see from the following results of experiments, in
which 300 parts of mercury were always employed, and from 400 to 450 of
water:--
Sulphur. Potash. Vermillion obtained.
114 75 330
115 75 331
120 120 321
150 152 382
120 180 245
100 180 244
60 180 142
The first proportions are therefore the most advantageous; the last,
which are those of M. Kirchoff himself, are not so good.
Brunner found that 300 parts of quicksilver, 114 of sulphur, 75 of
caustic potassa, and from 400 to 450 of water, form very suitable
proportions for the moist process; that the best temperature was 113°
F.; and that 122° was the highest limit of heat compatible with the
production of a fine colour.
The theory of this process is by no means clear. We may suppose that a
sulphuret of potassium and mercury is first formed, which is eventually
destroyed, in proportion as the oxygen of the air acts upon the
sulphuret of potassium itself. There may also be produced some
hyposulphite of mercury, which, under the same influence, would be
transformed into sulphuret of mercury and sulphate of potash.
Sulphuret of potassium and mercury furnish also vermillion, but it is
not beautiful. Red oxide of mercury, calomel, turbith mineral, and the
soluble mercury of Hahnemann, treated with the sulphuret of potassium,
or the hydrosulphuret of ammonia, are all capable of giving birth to
vermillion by the humid way.
The vermillion of commerce is often adulterated with red lead,
brickdust, dragon’s blood, and realgar. The first two, not being
volatile, remain when the vermillion is heated to its subliming point;
the third gives a red tincture to alcohol; the fourth exhales its
peculiar garlic smell with heat; and when calcined in a crucible with
carbonate of soda, and nitre in excess, affords arsenic acid, which may
be detected by the usual chemical tests.
VINEGAR MANUFACTORY, BY MALT. Annual produce, 100,000 gallons.
_Expenses for One Month._ _£ s. d._
Cost of material and fuel for 8,333 gallons,
at 8-3/4_d._ 303 16 2
Wages to 8 workmen, at 25_s._ per week 40 0 0
Salaries to clerks, manager, and traveller 83 6 8
Travelling expensesat 30 0 0
Three horses’ keep 7 10 0
Rent and taxes 25 0 0
-----------
_£_489 12 10
-----------
Expenses for 5 months, at 489_l._ 12_s._ 10_d._ 2448 4 2
Duty on 41,665 gallons, at 2_d._ 347 4 2
Stock of utensils 1500 0 0
------------
_£_4295 8 4
------------
Produce of 100,000 gallons, at 1_s._ 8_d._ _£_8333 6 8
Expenses for 12 months, at 489_l._
12_s._ 10_d._ _£_5875 18 0
Duty on 100,000 gallons,
at 2_d._ 833 6 8
Interest on capital, 4295_l._ 8_s._ 4_d._ 214 4 5
---------
6923 9 1
------------
Net profit _£_1409 17 7
------------
See ACETIC ACID.
VIOLET DYE, is produced by a mixture of red and blue colouring-matters,
which are applied in succession. Silk is dyed a fugitive violet with
either archil or brazil wood; but a fine fast violet, first by a crimson
with cochineal, without tartar or tin mordant, and after washing, it is
dipped in the indigo vat. A finish is sometimes given with archil. A
violet is also given to silk, by passing it through a solution of
verdigris, then through a bath of logwood, and, lastly, through alum
water. A more beautiful violet may be communicated by passing the alumed
silk through a bath of brazil wood, and after washing it in the river,
through a bath of archil.
To produce violets on printed calicoes, a dilute acetate of iron is the
mordant, and the dye is madder. The mordanted goods should be well
dunged.
A good process for dyeing cottons violet, is--first, to gall, with 18 or
20 pounds of nut-galls for every 100 pounds of cotton; second, to pass
the stuff; still hot, through a mordant composed of--alum, 10 pounds;
iron-liquor, at 1-1/2° B., and sulphate of copper, each 5 or 6 pounds;
water, from 24 to 28 gallons; working it well, with alternate steeping,
squeezing, airing, dipping, squeezing, and washing; third, to madder,
with its own weight of the root; and fourth, to brighten with soap. If
soda be used at the end, instead of soap, the colour called _prune de
monsieur_ will be produced; and by varying the doses of the ingredients,
a variety of violet tints may be given.
The best violets are produced by dyeing yarn or cloth which has been
prepared with oil as for the Turkey-red process. See MADDER.
For the violet _pruneau_, a little nitrate of iron is mixed with the
alum mordant, which makes a black; but this is changed into _violet
pruneau_, by a madder bath, followed by a brightening with soap.
VITRIFIABLE COLOURS; see ENAMELS, PASTES, POTTERY, and STAINED GLASS.
VITRIOL, from _vitrum_, glass, is the old chemical, and still the vulgar
appellation of sulphuric acid, and of many of its compounds, which in
certain states have a glassy appearance: thus--
Vitriolic acid, or oil of vitriol, is sulphuric acid; blue vitriol, is
sulphate of copper; green vitriol, is green sulphate of iron; vitriol of
Mars, is red sulphate of iron; and white vitriol, is sulphate of zinc.