like a white pillar issuing from the midst of the liquor, and
consisting of an infinite number of air bubbles inexpressibly small.
Nothing seems to condense in the cavity of the head, which always
remains clear, and without any visible humidity. The gutts which light
on the sides of the receiver, instead of forming a net-work thereon, as
Spirit of Wine doth when it is a little aqueous, spread to the breadth
of two inches or more, when they consist of true Æther. As soon as you
perceive this track begin to grow considerably narrower, the fire must
be put out; for what rises afterwards will be mixed with water, and
communicate that fault to the Æther already collected in the receiver.
"Then pour this ætherial liquor into a long bottle, and add to it an
equal quantity of well-water. Shake the bottle; the liquor will become
milky, and the true Æther will instantly separate, float upon the
water, and mix no more with it. Separate it then by a siphon, and keep
it in a glass bottle shut close with a glass stopple."
PROCESS II.
_Spirit of Wine combined with Spirit of Nitre. Sweet Spirit of Nitre._
Into an English retort of crystal glass put some highly rectified
Spirit of Wine; and, by means of a glass funnel with a long pipe,
let fall into your Spirit of Wine a few drops of the Smoking Spirit
of Nitre. There will arise in the retort an effervescence attended
with heat, red vapours, and a hissing noise like that of a live coal
quenched in water. Shake the vessel a little, that the liquors may mix
thoroughly, and that the heat may be equally communicated to the whole.
Then add more Spirit of Nitre, but in a very small quantity, and with
the same precautions as before. Continue thus adding Spirit of Nitre,
by little and little at a time, till you have put into the retort a
quantity equal to a third part of your Spirit of Wine. Let this mixture
stand quiet, in a cool place, for ten or twelve hours; then set it to
digest in a very gentle warmth for eight or ten days, having first
luted on a receiver to the retort.
During this time a small quantity of liquor will come over into the
receiver, which must be poured into the retort. Then distil with a
somewhat stronger degree of heat, but still very gently, till nothing
be left in the retort but a thick matter. In the receiver you will find
a spirituous liquor, of a quick grateful smell, which will excite a
very smart sensation on the tongue, but without any corrosive acrimony.
This is _The Sweet Spirit of Nitre_.
_OBSERVATIONS._
By this operation Spirit of Nitre is combined with Spirit of Wine;
these two liquors being united with each other, much in the same manner
as the Vitriolic Acid is with Spirit of Wine in Rabel's Water.
The proportion of the liquors which form this combination is not
absolutely determined, and the several authors who have written on
the subject differ much about it. Some require equal parts of the
ingredients; others again from two as far as ten parts of Spirit of
Wine to one of Spirit of Nitre. This depends on the degree to which the
Spirit of Nitre made use of is concentrated, and on the greater or less
acidity which your dulcified Spirit of Nitre is intended to have.
The Dispensatory of the College of Paris orders one part of Spirit of
Nitre distilled from dried clay, that is, of Spirit which doth not
smoke, to be mixed with two parts of rectified Spirit of Wine, and the
whole to stand in digestion for a month, without distilling the mixture
at all. This is a very good method: because the long digestion supplies
the place of distillation, and the Spirit of Nitre, not being highly
concentrated, doth not greatly alter the Spirit of Wine; besides that
many inconveniences, to be presently taken notice of, are by this means
avoided.
But as our design is not to describe such Chymical preparations only
as are commonly used in medicine, our plan requiring us to treat
particularly of those which may give any light into the fundamental
properties of bodies, the process here set down appeared the fittest
for our purpose; because the action which Spirit of Nitre exerts upon
Spirit of Wine is therein stronger and more perceptible.
One of the first particularities attending the mixture of those two
liquors, is the great effervescence, accompanied with violent heat,
abundance of fumes, and loud hissing, which arises as soon as the
Spirit of Nitre and the Spirit of Wine come into contact with each
other. There is great reason to think, that these phenomena are
produced only by the rapidity and vigour with which the Nitrous Acid
rushes into union with the inflammable part of the Spirit of Wine.
We observed, in treating of the Æther, that phenomena of the same
kind appear at the instant when the Vitriolic Acid unites with Spirit
of Wine: but on that occasion, how highly soever the Vitriolic Acid
be concentrated, all these effects are in a less degree than those
produced in the present experiment; because the Nitrous Acid, though
weaker than the Vitriolic, generally acts much more vigorously and
violently on the bodies with which it unites, than any other sort of
Acid.
Concerning these mixtures of Acids with Spirit of Wine, Mr. Pott
observes, that it is not a matter of indifference whether you pour the
Spirit of Wine upon the Acid, or the Acid on the Spirit of Wine; but
that every thing passes much more quietly, when the Acid is poured to
the Spirit of Wine, than when the contrary is done: and he gives the
true reason thereof; to wit, that when the Acid is poured on the Spirit
of Wine it finds in that liquor a great quantity of water, with which
it immediately unites; that this weakens it, and hinders it from acting
on the inflammable part with so much impetuosity as it otherwise would;
and therefore he advises that such mixtures be always made in this
manner. But it is evident that this advantage is gained only by mixing
the Acid with the Spirit of Wine very gradually, and drop by drop, as
directed in the process after Mr. Pott. For, if the two liquors were
to be mixed together suddenly, and all at once, it is certain that the
Acid would not meet with a single drop of phlegm more or less in that
way than in the other.
Therefore the chief, and, in some measure, the only precaution
necessary to be taken, in the making of such mixtures, to prevent the
violent effervescence and other inconveniences that may attend it, such
as explosion, and the bursting of the vessels, is to pour but a very
small quantity of one liquor into the other at a time, and to add no
more till the effervescence, and even the heat, produced by the first
portion, be entirely ceased. With these precautions you may proceed
either way, and be always sure that the vessels will not burst; because
it is in your power to add such a small quantity of liquor at a time,
as shall scarce produce a sensible effervescence. We own, however, that
Mr. Pott's observation is a very just one. There is even an advantage
in pouring the Acid to the Spirit of Wine, as he directs; which is,
that the mixture is a little sooner made, and without any danger.
We have shewn, that the Vitriolic Acid becomes aqueous and sulphureous
by mixing Spirit of Wine with it: the Nitrous Acid is changed by this
mixture in a manner no less remarkable. Mr. Pott observes, that when
Spirit of Nitre is dulcified, that is, when it is perfectly combined
with Spirit of Wine, it loses the disagreeable odour peculiar to it,
and acquires another that is quick and fragrant; it doth not afterwards
emit any red fumes; it rises with a less degree of heat than when pure;
it acts with less vigour on Fixed Alkalis and Absorbent earths. Lastly,
we shall here relate an experiment made by that Chymist, which seems to
prove that the Nitrous Acid loses its most characteristic properties,
and entirely changes its nature, by being combined with Spirit of Wine.
Mr. Pott examined the thick liquor left in the retort, when the
dulcified Spirit of Nitre is distilled off. By analyzing it he obtained
an acid liquor, of a yellow colour, and of a somewhat empyreumatic
smell. This Acid was followed by some drops of a red empyreumatic
Oil; and there remained, at the bottom of the distilling vessel, a
black, shining, charred matter, like that which remains after the
rectification of a fetid Oil.
The Oil extracted from this residue is a portion of that which helped
to constitute the Spirit of Wine; being separated therefrom by the
Nitrous Acid, in the same manner as that treated of in the preceding
process, and called _Sweet Oil of Vitriol_, is separated by the
Vitriolic Acid. But as the Nitrous Acid, which is weaker than the
Vitriolic, doth not so effectually decompose the Spirit of Wine, the
Oil, obtained in the present experiment, is in smaller quantity than
that procured in the distillation of a mixture of the Vitriolic Acid
with Spirit of Wine.
As to the Acid which Mr. Pott drew off in his experiment, there is
great reason to think it a part of that which was an ingredient in the
mixture; namely, of the Nitrous Acid. And yet Mr. Pott having saturated
with a Fixed Alkali one part of the residuum, which he had a mind to
examine before the Acid was separated from it by distillation, and
expecting this matter to contain a regenerated Nitre, he threw it on
a live coal; but was surprised to see it burn without the least sign
of detonation; and thence concluded, that the Nitrous Acid had changed
its nature. This experiment, he thinks, may furnish hints for the
transmutation of Acids; and he is of opinion, that the Nitrous Acid
loses its virtue of detonating, in the present case, only because its
inflammable part, to which it owes its distinguishing properties, hath
deserted it, and joined with that of the Spirit of Wine.
Indeed if the Acid obtained by Mr. Pott, which being reduced to a
Neutral Salt doth not detonate, derives its origin from the Nitrous
Acid that was combined with the Spirit of Wine, there is no doubt of
its being depraved in a peculiar manner, and having entirely changed
its nature. But may we not suppose it to have another origin? May
it not be the Acid of the Spirit of Wine itself, resulting from the
decomposition of that mixt in the distillation?
Mr. Navier, whom we mentioned in our Elements of the Theory, extracted
a very singular oily liquor from the mixture of Spirit of Wine and
Spirit of Nitre, without distillation, and even without the help of
fire. He put equal parts of the two liquors, by measure, not by weight,
into a bottle, which he stopped close with a good cork, fastened
down with pack-thread. Nine days afterwards he found about a sixth
part of the mixture separated from, and floating on, the rest of the
liquor. This was a very fine æthereal Oil, very limpid, and almost as
colourless as water.
In another experiment Mr. Navier substituted a solution of Iron in
the Nitrous Acid for pure Spirit of Nitre; and with this solution
he mixed an equal weight of Spirit of Wine. From the mixture, after
a fermentation which appeared in it, he obtained by the same method
an æthereal Oil, like that of his former experiment; except that
the latter, which was at first as colourless as the other, acquired
a redness in the space of about three weeks. He conjectures, with
probability, that this colour proceeded from some particles of Iron
which were united with it, and which gradually exhaled.
If a few drops of Oil of Tartar _per deliquium_ be poured on this Oil,
as soon as it is separated, there appears at first no sensible change
therein: but after some time needle-like crystals shoot in it, which
are a true regenerated Nitre; and if the bottle be then unstopped, the
liquor emits a most pungent nitro-sulphureous odour; which leaves no
doubt of this Oil's containing a Nitrous Acid. When it is thus freed of
its Acid, by means of the Oil of Tartar, it is much more volatile than
before.
Neither the Vitriolic nor the Marine Acid is capable of separating such
an Oil from Spirit of Wine: but the Nitrous Acid always produces it,
even when it is not concentrated, and doth not smoke.
It is very certain that this Oil derives its origin from the Spirit of
Wine: but there are not yet experiments enough made upon it, to enable
us to speak very accurately about the manner in which this liquor is
formed, or of the cause of its separation from the Spirit of Wine.
PROCESS III.
_Spirit of Wine combined with the Acid of Sea-salt. Dulcified Spirit of
Salt._
Mix together, little by little, in a glass retort, two parts of Spirit
of Wine with one part of Spirit of Salt. Set this mixture to digest for
a month in a gentle heat, and distil it, till nothing remain in the
retort but a thick matter.
_OBSERVATIONS._
The Acid of Sea-salt is much less disposed to unite with inflammable
matters than the other two mineral Acids; and therefore, though it be
ever so highly concentrated, when mixed with Spirit of Wine, it never
produces an effervescence comparable to that which is produced by the
Spirit of Nitre. Neither the proportion nor strength of the Spirit of
Salt, requisite to prepare the Sweet Spirit of Salt, are unanimously
agreed upon by Authors. Some direct equal parts of the two liquors;
while others prescribe from two to four or five parts of Spirit of Wine
to one part of Spirit of Salt. Some use only common Spirit of Salt;
others require the Smoking Spirit, distilled by means of Spirit of
Vitriol. Lastly, some order the mixture to be distilled, after some
days digestion; and others content themselves with barely digesting it.
The whole depends on the degree of strength which the Sweet Spirit of
Salt is intended to have. This composition, as well as the Sweet Spirit
of Nitre, is esteemed in medicine to be very aperitive and diuretic.
When the mixture of Spirit of Salt and Spirit of Wine is distilled,
there comes over but one liquor, which appears homogeneous. This is the
Sweet Spirit of Salt. The nature of the Marine Acid is not changed in
this combination: the Acid is only weakened and rendered more mild; but
in other respects it retains its characteristic properties.
Some authors pretend, that an Oil is obtained by distilling the
mixture for the Sweet Spirit of Salt; but others expressly deny the
fact. This variety may be occasioned by the quality of the Spirit of
Wine employed. It would not be surprising if a Spirit of Wine, which
contains much Oil that is unnecessary to its nature, and, as it were,
adventitious to it, should yield an Oil when distilled with Spirit of
Salt.
The thick residue, found in the retort after distillation, contains
the most ponderous part of the Acid, united with part of the Spirit of
Wine. If the distillation be continued to dryness, there remains in
the retort a black charred matter, much like that which is left by the
combinations of Spirit of Wine with the other Acids.
A sweet Spirit of Salt may also be prepared by digesting Spirit of
Wine with, or distilling it from, metallic compositions replete with
the Marine Acid adhering but slightly to them; such as Corrosive
Sublimate, and Butter of Antimony. Part of this Acid, which is very
highly concentrated, quits the metallic substance with which it is but
superficially combined, in order to unite with the Spirit of Wine. If
Butter of Antimony be used for this purpose, Mr. Pott, the author of
these experiments, observes, that a _Mercurius Vitæ_ precipitates;
which is nothing else, as we observed in its place, but the reguline
part of the Butter of Antimony deserted by its Acid.
PROCESS IV.
_Oils, or Oily Matters, that are soluble in Spirit of Wine, separated
from Vegetables, and dissolved by means of that Menstruum. Tinctures;
Elixirs; Varnishes. Aromatic Strong Waters._
Put into a matrass the substances from which you intend to extract a
Tincture, having first pounded them, or pulverized them if they are
capable of it. Pour upon them Spirit of Wine to the depth of three
fingers breadth. Cover the matrass with a piece of wet bladder, and tye
it on with pack-thread. Make a little hole in this bit of bladder with
a pin, leaving it in the hole to keep it stopped. Set the matrass in a
sand-bath very gently heated. If the Spirit of Wine dissolve any part
of the body, it will accordingly acquire a deeper or lighter colour.
Continue the digestion till you perceive that the Spirit of Wine gains
no more colour. From time to time pull out the pin, to give vent to
the vapours, or rarefied air, which might otherwise burst the matrass.
Decant your Spirit of Wine, and keep it in a bottle well corked. Pour
on some fresh Spirit in its stead; digest as before; and go on in this
manner, pouring on and off fresh Spirit of Wine, till the last come off
colourless.
_OBSERVATIONS._
It is commonly said, that Spirit of Wine is the solvent of Oils and
oily matters: but this proposition is too general; for there are
several sorts of Oils and oily matters which this menstruum will not
dissolve. Of this number are the Fat Oils, Bees-Wax, and the other Oily
compounds of that kind. Properly speaking, it dissolves but two sorts
of oily substances; namely, Essential Oils, and Balsams or Resins,
which are matters of the same kind, differing from each other only as
they are more or less thick; and Oils that are in a saponaceous state.
In our Elements of the Theory we have explained our opinion on
this head, from a Memoir on the subject printed among those of the
Academy for 1745. To repeat it in a few words: we take the cause of
the solubility of Oils in Spirit of Wine to be an Acid, which is
but superficially united with them, and so as still to retain its
properties.
The principal proofs on which we found this opinion are drawn from that
property of Essential Oils, Balsams, and Resins, which are naturally
soluble in Spirit of Wine, that they become so much the less soluble
in this menstruum, the oftener they are distilled or rectified; and
from that property which Fat Oils, or other Oily matters, naturally
indissoluble in Spirit of Wine, possess, of becoming more and more
soluble therein the oftener they are distilled. We shewed that
distillation lessens the solubility of Essential Oils, Balsams, and
Resins, only by depriving these substances of part of the manifest
Acid which they contain, and which is the cause of their solubility;
and that Fat Oils, and other oily matters, naturally indissolvable
in Spirit of Wine, are by the same operation rendered capable of
dissolving therein, only because it discovers, and partly extricates,
an Acid, which is naturally combined with them so intimately that it is
entirely deprived of action, and all its properties perfectly masked.
If these principles be well attended to, and if it be recollected
withal, that Spirit of Wine unites with Water preferably to Oils;
insomuch that, if it be mixed with water when it hath dissolved an Oil,
it quits the Oil to unite with the Water; that for the same reason
it is not capable, when very aqueous, of dissolving any Oil, seeing
that, as Oil and water are not susceptible of contracting any union,
it must then desert its phlegm to unite with the Oil; which it cannot
do, because it hath a greater affinity with phlegm than with Oil; and,
lastly, that if Oil be combined with any saline substance, which makes
it soluble in water; that is, if it be in a saponaceous state, it will
then remain dissolved in Spirit of Wine, without being precipitated
by water; or will be dissolved by a very aqueous Spirit of Wine, and
frequently much better than by a highly rectified Spirit: if these
things, I say, be considered, we shall easily perceive what must be
the effect of digesting Spirit of Wine with any vegetable substance
whatever.
Spirit of Wine dissolves all the Essential Oil, Balsam, and Resin
contained in any vegetable; and as these matters are not soluble
in water, they may be separated from the Spirit in which they are
dissolved, by lowering it with much water. It instantly becomes white
and opaque, like milk; the oily parts gradually unite, and form
considerable masses, especially if they be resinous. This is the method
commonly made use of to extract the Resin of Scammony, Jalap, Guaiacum,
and several other vegetable substances, which it would be difficult to
procure by any other means.
If the matters digested with Spirit of Wine contain any saponaceous
juices, the Spirit will take up those juices also. But as soaps
are soluble in water, as well as in Spirit of Wine, they cannot be
separated, by the addition of water, from the Spirit in which they are
dissolved. Whatever quantity of water therefore you mix with a Spirit
that is impregnated with such juices, no separation thereof will be
produced; and for the same reason the saponaceous matters will be
dissolved by a very aqueous Spirit of Wine.
Spirit of Wine impregnated with such parts of any vegetable substance,
as it is capable of dissolving, is commonly called a _Tincture_.
Several Tinctures mixed together, or a Tincture drawn from sundry
vegetable substances at the same time, and in the same vessel, take the
name of an _Elixir_. Tinctures or Elixirs impregnated with Resinous
matters only are true _Varnishes_. All these preparations are made in
the same manner; to wit, as directed in our process. We shall only add
here, that if the substances from which a Tincture or Elixir is to be
made contain too much moisture, it is proper to free them from it by a
gentle desiccation; especially if you design that the Tincture should
be well impregnated with the oily and resinous parts: for their excess
of moisture uniting with the Spirit of Wine would weaken it, and render
it unable to act on those matters, which it cannot dissolve when it is
aqueous.
Vegetable substances which have been repeatedly digested with different
parcels of Spirit of Wine, till the last would extract nothing, are
deemed to be exhausted of all their Essential Oils, and saponaceous
juices: but if they contain moreover any Fat Oil, Wax, or Gum, these
principles will still remain therein after the digestion, in the same
quantity as before; because Spirit of Wine is incapable of dissolving
them.
With regard to the Fat Oil and Wax, this is not at all surprising: we
have explained in another place why these matters are indissoluble
by Ardent Spirits: but as for the Gum, it would seem, according to
the general principles above-mentioned, that it should be soluble
in that menstruum, even with more ease than Resins; as it consists
almost entirely of water, with which Spirit of Wine is known to unite
more easily than with Oils. Indeed there is also a little Oil in its
composition: but this Oil seems to be in a perfectly saponaceous state;
for Gum dissolves wholly and easily in water, without lessening its
transparency in the least.
I own that it is extremely difficult to give a very satisfactory
account of this matter. We may however venture to throw out some
conjectures concerning it, deduced from what hath been already said,
relating to the cause of the solubility of Oils in Spirit of Wine.
We shewed that the Oils which dissolve in this menstruum derive
that property from a manifest Acid, which is united with them but
superficially, and in such a manner as to retain all its virtue; but
that if this same Acid be too intimately united with the Oil, so as to
have no manifest power, but be in a manner destroyed, and converted as
it were into a Neutral Salt, it will not then produce this effect.
A modern author[13] relates two experiments which agree very well with
this opinion, and indeed confirm it. He mixed together Oil of Vitriol
and Oil of Turpentine, with a view to imitate by art a bituminous
matter; which, we know, is not at all, or at least scarcely, soluble in
water. These two matters being united together produced a red, thick
compound, which by evaporation became like a natural Bitumen.
[13] Mr. Eadows, in a little English book, entitled _The Modern
Apothecary_.
The author observes, that when this mixture is just made it dissolves
in Alcohol; but that in some time it changes its nature, and
communicates scarce any part of its substance to that solvent. Now
whence can such a difference arise, but from this, that when the
mixture is new, the Acid is as yet but superficially united with the
Oil, and combines with it more and more intimately, as the mixture
grows older.
The same author, having repeated the experiment with Spirit of Vitriol,
obtained a compound which continued always very soluble in Spirit of
Wine: because Spirit of Vitriol being much weaker and more aqueous than
Oil of Vitriol, was incapable of combining so closely with the Oil of
Turpentine, as that concentrated Acid did in the former experiment. By
the by, there is great reason to believe that the very intimate union
of a mineral Acid with an oily matter is the true cause why Bitumens
will not dissolve in Spirit of Wine.
It seems therefore pretty probable, that the Acid which makes the Oil
of Gummy matters soluble in water, and reduces it to a saponaceous
state, is so intimately united with that Oil, that it loses its
properties, and is in a manner converted into a Neutral Salt. Now we
know that such Salts are soluble in water, but are not so, for the
most part, in Spirit of Wine.
If your Tinctures or Elixirs be not so strong or so saturated as you
desire, you may by distillation abstract part of the Spirit of Wine
which they contain, and by that means give them such a degree of
thickness as you judge proper. But the Spirit of Wine thus drawn off
constantly carries along with it a good deal of the aromatic principle.
It is a truly _Aromatic Strong Water_. This Spirit of Wine also
carries up with it a portion of thin Oil, which is so much the more
considerable as the degree of heat employed is greater: and this is the
reason why it becomes of a milky colour when mixed with water.
If you intend to make an Aromatic Strong Water only, you need not
previously extract a Tincture from the vegetable substance with which
you mean to prepare your water: you need only put it in a cucurbit,
pour Spirit of Wine upon it, and distil with a gentle heat. By this
means you will obtain a Spirit of Wine impregnated with all the odour
of the plant.
CHAP. III.
_Of_ TARTAR.
PROCESS I.
_Tartar analyzed by distillation. The Spirit, Oil, and Alkaline Salt of
Tartar._
Into a stone retort, or a glass one coated with lute, put some white
Tartar broken into small bits, observing that one half, or at least
a full third, of the vessel be left empty. Set your retort in a
reverberating furnace. Fit on a large ballon, having a small hole
drilled in it; lute it exactly with fat lute, and secure the joint
with a linen cloth smeared with lute made of quick-lime and the white
of an egg. Apply at first an exceeding gentle heat, which will raise
a limpid, sourish, pungent water, having but little smell, and a
bitterish taste.
When this first phlegm ceases to come off, increase your fire a little,
and make the degree of heat nearly equal to that of boiling water. A
thin limpid Oil will rise, accompanied with white vapours, and with a
prodigious quantity of air, which will issue out with such impetuosity,
that if you do not open the little hole in the receiver time enough to
give it vent, it will burst the vessels with explosion. An acid liquor
will rise at the same time. Continue the distillation, increasing the
heat by insensible degrees, and frequently unstopping the little hole
of the receiver, till the elastic vapours cease to issue, and the oil
to distil.
Then raise your fire more boldly. The acid Spirit will continue to
rise, and will be accompanied with a black, fetid, empyreumatic,
ponderous, and very thick Oil. Urge the fire to the utmost extremity,
so that the retort may be of a perfect red heat. This violent fire will
raise a little Volatile Alkali, besides a portion of Oil as thick as
pitch. When the distillation is finished, you will find in the retort
a black, saline, charred matter, which grows hot when wetted, attracts
the moisture of the air, runs _per deliquium_, and hath all the
properties of a Fixed Alkali.
This mass, being exposed to a naked fire in the open air, burns,
consumes, and is reduced to a white ash, which is a fiery, caustic,
Fixed Alkali.
_OBSERVATIONS._
The matters qualified to produce a spirituous liquor by fermentation,
do not all contain the just and accurate proportion of Acid necessary
to constitute an Ardent Spirit. Many of them, the juices of fruits
for instance, and especially that of the Grape, are replete with a
super-abundant quantity of Acid, more than concurs to form that product
of fermentation. This super-abundant Acid, combined with some of the
Oil and earth contained in the fermented liquor, produces a sort of
Salt, which hangs for a while suspended in that liquor, but after some
time, when the Wine stands quiet in a cool place, separates from it,
and forms a stone-like incrustation on the inside of the vat in which
the Wine is kept. This matter is called _Tartar_.
The Lees of Wine resemble Tartar, in as much as they contain, and yield
when analyzed, the same principles; but they differ from it in this,
that they contain, moreover, a greater quantity of earth, of phlegm,
and a little Ardent Spirit, which are only mixed, but not united, with
the tartarous Acid.
The residue, or sort of extract, which remains in the cucurbit after
Wine hath been deprived of its Ardent Spirit by distillation, hath also
a great conformity with Tartar. It even contains that portion of Tartar
which remained suspended in the Wine at the time of its distillation:
and accordingly this residue of Wine, being analyzed, yields the same
principles with Tartar.
Hence we see, that liquors, which have undergone the spirituous
fermentation, consist of an Ardent Spirit and a Tartarous Acid
suspended in a certain quantity of Water.
In the analysis of Tartar there are several things worthy of notice.
The first is, the vast quantity of Air that this mixt body yields when
it begins to be decomposed. The chief difficulty attending its analysis
arises from this air; which issues out and exerts its elastic force
with such impetuosity, that all the precautions above-mentioned are no
more than necessary to prevent the bursting of the vessels.
The singular nature of the thin limpid Oil, which rises with this
air, after the first acid phlegm, deserves likewise our particular
attention. This Oil is one of the most penetrating we know. Boerhaave,
who distilled Tartar without having a vent-hole in his receiver, was
obliged, in order to prevent its bursting, to apply it to his retort
with a lute so weak that most of the elastic vapours might perspire
through it; and he observed, that, though the neck of his retort
entered above five inches into the mouth of his receiver, and was
luted on as closely as possible with such a lute, yet this light Oil
of Tartar constantly returned back again, as it were, and pervaded the
substance of the lute, so that a good deal of it dropped in a dish
placed on the outside on purpose to receive it. This Oil is probably
rendered so active and subtile, only by having been exceedingly
attenuated by the fermenting motion. This experiment is one of those
which sufficiently prove the necessity of employing receivers having a
small vent-hole, that may be opened and shut as occasion requires.
The last remark we shall make, on the productions of Tartar by
distillation, relates to the _caput mortuum_ found in the retort when
the operation is finished. This residue is very different from that
which other vegetable matters afford: for, when they are decomposed in
close vessels, they leave nothing but a mere charred matter, in which
no saline property appears, and from which no Fixed Alkali can be
obtained, but by carrying their analysis to the utmost; that is, by
burning them in the open air. Tartar, on the contrary, only by being
distilled in close vessels, without burning it afterwards in the open
air, is changed into a substance which hath all the properties of a
Fixed Alkali. This is probably owing to the Tartar's containing the
principles requisite to form a Fixed Alkali in a much greater quantity
than they are to be found in any other substance. As Tartar thus
alkalizated in close vessels still contains much inflammable matter,
it might be employed with advantage as a reducing flux, in several
operations of metallurgy.
Of all the vegetable matters we know, calcined Tartar yields the
greatest quantity of Fixed Alkali; which is likewise very pure, and
therefore much used in Chymistry.
Burnt Lees of Wine also afford a great quantity of Fixed Alkali,
which is of the same nature with that of Tartar. This Salt is used in
different trades, and particularly in Dying. The French Vinegar-makers
collect quantities of these Lees, which they make up into cakes and
dry: while it is in this state they call it _Gravelle_ or _Gravelée_;
and _Cendre Gravelée_ when it is burnt.
If the extract of Wine, which remains after the Spirit is drawn off,
be gently evaporated to dryness, and that dry matter burnt like Tartar
or _Gravelle_, it will make a sort of _Cendre Gravelée_ very rich in
alkaline Salt.
PROCESS II.
_The Depuration of Tartar. Cream and Crystals of Tartar._
Reduce to a fine powder the Tartar you intend to purify, and boil it in
twenty-five or thirty times as much water. Filter the boiling liquor
through a flannel-bag, and then gently evaporate some part of it: there
will soon form on its surface a saline crust, which is the _Cream of
Tartar_. Let your liquor cool, and there will adhere to the sides of
the vessel a great quantity of a crystallized saline matter, which is
_Crystal of Tartar_.
_OBSERVATIONS._
Tartar, when taken out of the vats in which it forms, is mixed with a
considerable quantity of earthy parts, which are not intimately united
therewith, but adulterate it. This extraneous earth makes about two
fifths of the whole weight of common Tartar; but white Tartar, which is
the best, contains but about a third part of earth.
The method of refining Tartar, and freeing it from this adventitious
earth, is very simple, as appears from the process. Earthy matters,
which are not intimately combined with an Acid in the form of a Neutral
Salt, are not dissoluble in water: for which reason the water, in which
crude Tartar is boiled, dissolves the saline part only, which passes
with it through the filter; but doth not dissolve the earth of the
Tartar, because that earth is not combined with the saline part, and so
being only suspended in the liquor remains on the filter.
The saline parts of the Tartar, though they are now separated from the
gross earth with which they were mixed, are not yet perfectly pure.
These first Crystals of Tartar have a disagreeable russet colour, and
are not transparent: this is owing to their being coated over, as it
were, with a fatty matter, which also is foreign to their nature, and
may be separated from them without decomposing them in the least.
The crystals of Tartar are but seldom perfectly depurated in Chymical
Laboratories; because the operation doth not usually succeed well on
small quantities: but there are manufactories which do it by the great,
and supply the Chymists, as well as the several tradesmen, with very
fine and very pure Crystals of Tartar. These manufactories are chiefly
set up in the neighbourhood of Montpelier. Mr. Fifes, a celebrated
Professor of Medicine, hath in the Memoirs of the Academy for 1725
described the operation as performed in one of these works. He tells
us, that having separated the earthy part from the Crystals of Tartar,
by boiling and filtering, they dissolve them again, and boil them in
large caldrons, mixed with a white saponaceous earth, which cleanses
and whitens them to perfection.
The saponaceous earth is found near the works; but it is not the
only one that may be employed for this purpose; since, as Mr. Fifes
observed, they have successively made use of several different earths
in that very work, and that the earth they now use hath not been long
employed. There is reason to think that most saponaceous earths might
answer the purpose of refining Crystal of Tartar: but one necessary
condition is, that they be altogether indissoluble by Crystal of
Tartar, which being acid dissolves many sorts of earth; for, if they
have not this quality, they will form a Neutral Salt with the saline
part of the Tartar, the nature of which they will entirely change, and
convert it into soluble Tartar, as will appear by the experiments that
follow.
CHAP. IV.
CRYSTAL _of_ TARTAR _combined with several_ SUBSTANCES.
PROCESS I.
_Crystal of Tartar combined with Absorbent Earths. Soluble Tartars._
Boil an Absorbent Earth, such as Chalk, in a pan with water; and, when
you perceive the Earth thoroughly divided, and equally distributed
through the water, throw into a pan, from time to time, some pulverized
Crystal of Tartar, which will excite a considerable effervescence.
Continue those projections, till you observe no effervescence excited
thereby. All the Absorbent Earth, which obscured the transparency of
the water, and gave it an opaque white colour, will gradually disappear
as the Crystal of Tartar combines with it; and when the combination is
perfected, the liquor will be clear and limpid. Then filter it, and
there will be left on the filter but a very small quantity of earth.
Evaporate all the filtered liquor with a gentle heat; and then set it
in a cool place to shoot. Crystals will form therein, having the figure
of flat quadrangular prisms, with almost always one, sometimes two, of
the angles of the prism shaved down, as it were; and then the surfaces
at each end are oblique, answering to those depressed angles. These
crystals are a Neutral Salt, which readily dissolves in water; a true
_Soluble Tartar_.
_OBSERVATIONS._
Crystal of Tartar is a saline substance of a singular nature. Though
it crystallizes like a Neutral Salt, yet it is not one: it hath
only the form of one; its principal properties being those of an
Acid. Nevertheless it is not a pure Acid; for it is united with a
certain quantity of Oil and of earth, which give it the property
of crystallizing, and it is scarce dissolvable in water. It is a
middle substance between an Acid and a Neutral Salt. It is an Acid
half-neutralized; on which account it is capable of acting like an
Acid on all substances soluble by Acids, and so of being converted
into a perfectly Neutral Salt by combining with them to the point of
saturation.
In the experiments made to neutralize Crystal of Tartar, Fixed Alkaline
Salts alone were formerly used. Messrs. Duhamel and Grosse were the
first who discovered that Absorbent Earths might be substituted for
Alkalis, and would produce nearly the same effects on Crystal of
Tartar. The experiments made by these two Academicians in conjunction
are circumstantially related in two curious Memoirs on this subject,
given in by them jointly, and printed with those of the Academy for
1732 and 1733. From these Memoirs we took the process here given, and
shall also borrow from thence most of the remarks we are now going to
make.
Stone-lime holds, as it were, the middle place between mere Absorbent
Earths and Fixed Alkalis. Now, seeing Crystal of Tartar may be
converted into a Neutral Salt by either of these two substances,
it follows, that lime ought to produce the same effect upon it.
Accordingly Messrs. Duhamel and Grosse found it to be so upon trial:
having formed, with _Lac calcis_ and Crystal of Tartar, a Neutral
Salt perfectly like that which results from the union of that saline
matter with Chalk. _Cremor calcis_, or that salino-terrene pellicle
which forms on lime-water, produced the same effect: but, what is most
singular is, that lime-water itself, though it be clear and limpid,
and consequently doth not seem to contain any earthy particles,
produced nevertheless a great effervescence with Crystal of Tartar, and
neutralized it as perfectly as _Cremor calcis_, or water ever so much
impregnated with Chalk. This arises from hence, that a great quantity
of the salino-terrene matter, which forms the _Cremor calcis_ is
dissolved in the lime-water.
Though lime-water neutralizes Crystal of Tartar as perfectly as Chalk
does, and though the Crystals of soluble Tartar, or neutralized Tartar,
thereby produced, be like those which have Chalk for their basis, yet
Messrs. Duhamel and Grosse observed some differences, worthy of notice,
between the phenomena accompanying the production of these two Neutral
Salts, which resemble each other so much that they seem but one and the
same species of Salt. The principal difference consists in this, that
the water containing the Tartar neutralized by Chalk is very limpid,
and leaves but a very small quantity of earth on the filter; whereas
the lime-water, with which Tartar hath been neutralized, leaves on the
filter a considerable quantity of earth.
This must appear the more surprising, that the water replete with Chalk
was, before its union with the Crystal of Tartar, turbid and opaque;
whereas the Lime water was at first clear and limpid. Messrs. Duhamel
and Grosse suspect this to arise from hence, that the effervescence
excited, while the Crystal of Tartar dissolves the matter contained in
lime-water, is greater than that which is produced by its union with
Chalk suspended in water.
"If we consider," say they, "that in a great effervescence a
considerable quantity of the acid Spirit is evaporated, we shall easily
perceive, that, the more of that Spirit escapes, the more of the earth
of the Tartar will be precipitated. Now, as the effervescence with
lime-water is more considerable, and as there is less alkaline earth to
check, as it were, and restrain the Acid, than in the experiment with
Chalk, a greater quantity of the acid Spirit may escape; which being
entirely lost will cause more earth to precipitate in this case than
in the other, where the Acid is all at once attracted by a great deal
of alkaline earth: and accordingly this was the reason that our Tartar
dissolved by Chalk deposited, in crystallizing, a grey earth, which was
scarce perceivable in the experiment made with Lime-water.
"Yet perhaps," say they, "an Acid, which we suspect to be contained
in lime, may have partly occasioned the precipitation of this earth."
The existence of this Acid, which these gentlemen at that time only
suspected, hath been since demonstrated by several experiments, and
particularly by those which Mr. Malouin hath published. This Acid
is the Vitriolic, which, in combination with some of the earth of
the lime, forms a sort of Selenitic Salt; which adds greatly to the
probability of Messrs. Duhamel and Grosse's last conjecture. I shall
now explain how I conceive the Vitriolic Acid in lime may occasion the
copious precipitate which falls in lime-water, when Crystal of Tartar
is neutralized by it.
The quantity of Vitriolic Acid contained in lime is very
inconsiderable; so that to convert it into a Neutral Salt requires
its intimate union with a very small quantity of the earthy and
absorbent parts. Hence it comes to pass, that, when water is poured
upon quick-lime, in order to make the Lime-water, it in some sort
divides the lime into two parts. All the particles of Absorbent Earth,
which had not contracted an union with the Acid, are at first barely
suspended in the liquor, the transparency of which they destroy, giving
it an opaque white colour; and this is what makes the _Lac calcis_:
but they soon separate from it, and fall to the bottom, in the form
of a precipitate; because they are not soluble in water. By this
precipitation the liquor becomes limpid, and remains impregnated only
with such of the earthy parts as are united with the Vitriolic Acid,
in the form of a kind of Neutral Salt, and have by that union acquired
solubility. But the Vitriolic Acid finding many more Absorbent parts in
the lime than were necessary to neutralize it, in a manner over-dosed
itself with earthy parts, and thereby exceeded the bounds of a perfect
Neutrality.
On the other hand, it hath been shewn, that Crystal of Tartar is an
imperfect Neutral Salt. Now these two Salts, which are neither of them
perfectly Neutral, differ from a perfectly Neutral Salt by properties
directly opposite to each other; seeing the Selenitic matter in Lime
exceeds in its absorbent or alkaline quality, and Crystal of Tartar
exceeds, on the contrary, in acidity.
What must be the consequence, therefore, of mixing these two saline
matters together? The same as when an Acid is mixed with a Fixed
Alkali; that is, the Salt which exceeds in acidity will combine with
the super-abundant alkaline earth of the Selenitic Salt; so that these
two saline matters will both become perfectly Neutral Salts. Yet these
two Neutral Salts have not the same degree of solubility in water.
The neutralized Crystal of Tartar dissolves very readily in water,
and is for that reason called Soluble Tartar: the Selenitic Salt, on
the contrary, is hardly dissolvable in it at all. Now it is a rule
that, when two Salts of this nature meet together, the most soluble
always remains united with the water, exclusive of the other, which
is forced to precipitate. This I imagine to be what happens in the
present case; and the precipitate which we see fall, in the lime-water
employed to neutralize Crystal of Tartar, seems to me to be no other
than the Selenitic Salt of the Lime; which, being less soluble than the
neutralized Tartar, gives place to it, and separates from the liquor.
Indeed we cannot, in my opinion, account for the precipitate under
consideration, any other way, than by supposing it to be a portion
either of the earth of the Crystal of Tartar, or a portion of the
Lime. Now, either of these earths is dissolvable by Acids; whereas the
precipitate in question, according to the observations of Messrs.
Duhamel and Grosse, is not so: and this ought to be the case, if the
precipitate be nothing but the selenitic Salt of the Lime, which being
a Neutralized Salt, partly constituted by the most powerful of all the
Acids, must be unalterable by any Acid whatever.
Messrs. Duhamel and Grosse made a great many experiments on the
combinations of Crystal of Tartar with different sorts of earths. The
result of the whole is, that there are some earths which this Acid
dissolves, and which contract such an union with Crystal of Tartar,
that they not only change its external character, that is, its tendency
to crystallize, and its indissolubleness in cold water, but also
entirely alter its taste and other qualities. In a word, those earths
produce on this Salt all the effects of alkaline Salts. These earths
are such as are called Absorbent Earths; stone-lime, animal-lime,
cretaceous earths, a portion of calcined gypsum, and of potash; in
short, all such as distilled vinegar is capable of dissolving: this
is the mark by which those earths, which are qualified to neutralize
Crystal of Tartar, and to render it soluble, may be distinguished.
Messrs. Duhamel and Grosse found also upon trial, that there are other
earths, on the contrary, which are, in a manner, inaccessible to the
Acid of Crystal of Tartar; that they take up, indeed, the grossest and
redundant Oil of the Tartar, but without affecting its saline part
at all: and if these earths are ever observed to form any union with
the Crystals of Tartar, as happens in the refineries near Montpelier,
that union is only superficial, not intimate; and therefore it alters
none of the characters of the Salt. Among these earths are the clayey,
bolar, sandy earths, and others of that kind. Hence Messrs. Duhamel and
Grosse conclude, that these are the earths which ought to be employed
in the purification and whitening of Crystal of Tartar. Vinegar is here
also the test by which it may be known whether an earth intended for
this purpose be fit for it: for you may be sure that it will form no
union with Crystal of Tartar, if the Acid of Vinegar be incapable of
dissolving it.
PROCESS II.
_Crystal of Tartar combined with Fixed Alkalis. The Vegetable Salt.
Saignette's Salt. The Decomposition of Soluble Tartars._
In eight parts of water dissolve one part of a very pure alkaline Salt,
perfectly freed from the phlogiston by calcination. Heat this lixivium
in a stone pan set on a sand-bath, and from time to time throw into
it a little powdered Cream or Crystal of Tartar. Each projection will
excite a great effervescence, attended with many bubbles, which will
rise to a considerable height one over the other. Stir the liquor when
the effervescence ceases, and you will see it begin again.
When no effervescence appears upon stirring the liquor, add a little
more Cream of Tartar, and the same phenomena will be renewed. Go on
thus till you have obtained the point of perfect saturation.
Then filter your liquor. If the Alkali you made use of was the Salt of
Soda, evaporate your liquor quickly to a pellicle, and there will shoot
in it crystals of nine sides, resembling a coffin; the bottom part
thereof being concave, and streaked with a great many parallel lines;
and this is _Saignette's Salt_. If you have employed any other Alkali
but Soda, or the basis of Sea-salt, evaporate your liquor slowly to the
consistence of a syrup: let it stand quiet, and there will form in it
crystals having the figure of slatted parallellopipeds; and this is the
_Vegetable Salt_, or _Tartarized Tartar_.
_OBSERVATIONS._
Seeing pure Absorbent Earths are capable of neutralizing Crystal of
Tartar, and converting it into Soluble Tartar, there is still more
reason to expect that Fixed Alkalis should possess the same property,
as they have a much greater affinity with Acids: and accordingly
Crystal of Tartar always forms, with every species of these salts, a
Neutral Salt which is a Soluble Tartar.
A Soluble Tartar, formed by the union of Crystal of Tartar with Tartar
converted into an Alkali by fire, hath been long used in medicine as
a gentle saponaceous purgative, known by the names of _Tartarized
Tartar_, or the _Vegetable Salt_. But the Soluble Tartar, prepared
by combining Crystal of Tartar with the Alkali of Soda, which, as we
remarked before, is analogous to the basis of Sea-salt, and different
from all other Alkalis, was not well known to Chymists till the year
1731, when M. Boulduc published the preparation in a Memoir printed in
the Academy's collection for that year[14].
[14] It could not be any longer concealed; for M. Geoffroy having made
some experiments on the same subject, without knowing any thing of
what M. Boulduc had done, likewise discovered it. See the History of
the Academy for 1731, p. 35.
Not but that it was very much used before that time: for it had
been for several years in high reputation, and prescribed instead
of Tartarized Tartar, which became almost quite neglected. But M.
Saignette, a physician of Rochelle, who was the first inventor and
vender of this Salt, did not publish the preparation of it, which he
kept as a secret: and this probably contributed not a little to the
great esteem which this medicine had acquired; for men are naturally
inclined to put a much greater value on secrets, than on what is
universally known. He gave it the name of _Sal Polychrestum_; and the
public called it also _Saignette's Salt_, and _Rochelle Salt_. Since
the discoveries of M. Geoffroy and M. Boulduc were published, the
method of preparing this Salt hath been no secret; it was described in
Dispensatories, and every apothecary hath made it ever since.
Saignette's Salt, as well as every other Soluble Tartar, melts when
laid on live coals, boils up, emits smoke, and leaves a black charred
matter behind. This resemblance of Saignette's Salt to Tartarized
Tartar, joined to the smell of the vapour which exhaled in burning it,
and is the same with that of Tartar, were the first notices that led
M. Boulduc to suppose this Salt to be a soluble Tartar. On examining
the alkaline coal produced by the calcination, and comparing it with
that left by Tartarized Tartar, he perceived there was some difference
between them. At last his friend, M. Grosse, having advised him, as he
tells us in his Memoir, to combine Crystal of Tartar with the Salt of
Soda, and to examine the new Salt that would result from their union,
M. Boulduc immediately suspected that it must produce a species of
Soluble Tartar, which might possibly prove to be the Salt in question.
Nor was he mistaken in his conjecture: for with these two saline
substances he actually composed a Salt perfectly like Saignette's.
Under the head of Borax we remarked that it contains an Alkali like
the basis of Sea-salt. This Alkali is not perfectly neutralized by
the sedative Salt, which is also contained in Borax: for its alkaline
properties are so perceptible as to have led some Chymists to think
that Borax was only an Alkali of a particular kind. This induced M. le
Fevre, a Physician at Uzes, and one of the Academy's correspondents,
to combine Crystal of Tartar with Borax, and to examine the result. He
communicated to the Academy his experiments on this subject; by which
he found that the combination of these two saline matters forms a
Soluble Tartar, but greatly different from Saignette's Salt; especially
in that it doth not crystallize, but remains in the form of a gummy
matter, and retains all the acidity natural to pure Cream or Crystal of
Tartar: a circumstance which is very remarkable.
Mr. Lemery had the curiosity to repeat M. le Fevre's experiment, and
found that this singular Soluble Tartar had the properties ascribed to
it by the inventor. The process he recommends for making the experiment
with success is as follows:
"Take four ounces of Crystal of Tartar finely pulverized, and two
ounces of Borax carefully powdered, and put these two Salts into
a flint-glass body. Pour on them two ounces of water, and set the
cucurbit into a sand-bath. Warm it with a gentle fire, and then
increase the heat so as to make the liquor boil for a quarter of
an hour; which will produce a perfect dissolution of the Cream of
Tartar and Borax. After the dissolution of these two Salts united
together, the liquor will remain clear and limpid, though the boiling
hath dissipated a good deal of it. If the liquor be still further
evaporated, the remainder will have the consistence of Honey, or
Turpentine: and, if the evaporation be carried still farther, with a
gentle heat, the matter remaining will in colour resemble the gum of a
plumb-tree, and yield to pressure as that does; and, if it be exposed
to the air in a damp place, it will grow moist and run, almost like
Salt of Tartar:" a new and singular property, which belongs neither to
Borax nor to Crystal of Tartar, when they are not combined together.
All Soluble Tartars are easily decompounded, by means of a certain
degree of heat. They yield in the distillation the same principles as
Tartar; and the Alkali that remains, when they are perfectly calcined,
consists of that which the Tartar naturally affords, and of the
alkaline matter with which it was converted into a Neutral Salt.
These Neutral Salts, resulting from the union of Crystal of Tartar with
any alkaline matter, are also decompounded by all the Acids, even by
vinegar, which nevertheless is an Oily Vegetable Acid, and consequently
of the same kind with Crystal of Tartar. The reason of this is that
the Acid of Vinegar, though blunted by much phlegm and oil, must be
considered as a free and pure Acid, when compared with Crystal of
Tartar; which is still more embarrassed with heterogeneous matters, so
as to be a semi-neutral Salt.
When Soluble Tartar is decompounded by an Acid, the Crystal of Tartar,
which helped to constitute the Neutral Salt, is then wholly recovered.
This saline matter, being separated from that which rendered it soluble
in water, ceases now to be so, and for that reason precipitates to the
bottom of the liquor.
The Neutral Salts, resulting from the decomposition of Soluble Tartar
by an Acid, differ according to the Acid made use of. From Saignette's
Salt decompounded by the Vitriolic Acid M. Boulduc obtained a true
Glauber's Salt, and a precipitate of Crystal of Tartar: and this he
justly adduces as a demonstrative proof, that Saignette's Salt is no
other than Crystal of Tartar neutralized by a Fixed Alkali analogous to
the basis of Sea-salt.
Though all Soluble Tartars may be decompounded by Acids, as hath just
been said, yet they do not all forsake their bases with equal facility.
Messrs. Duhamel and Grosse found that, in this respect, they observe
the following order, beginning with those which afford the readiest and
most copious precipitate: viz. Soluble Tartar made 1. with Potash; 2.
with Chalk; 3. with uncalcined Oyster-shells; 4. with Stone-Lime; 5.
with calcined Oyster-shells; 6. with Salt of Tartar; 7. with Salt of
Soda; 8. and lastly, Tartar made soluble with Borax is not precipitated
by distilled vinegar.
It is not easy to account for this difference between Soluble Tartars.
If the Salt of Soda were more alkaline than Salt of Tartar, and Borax
more alkaline than the Salt of Soda, it might be conjectured that
the more alkaline the matters are with which Crystal of Tartar is
neutralized, the closer is the union it contracts with them; since
it is plain, from what hath been said on this subject, that though
Soluble Tartars, which have for their basis Absorbent Earths only, not
converted into Lime, are more easily decompounded than those which are
rendered soluble by Limes; and these again more easily than those which
have a Fixed Alkali for their basis. But, on the contrary, the Salt of
Soda is less alkaline than Salt of Tartar, and Borax still less than
the Salt of Soda.
PROCESS III.
_Crystal of Tartar combined with Iron. Chalybeated Tartar. Tincture of
Steel with Tartar. Soluble Chalybeated Tartar._
Mix four ounces of Iron, in filings, with one pound of white Tartar,
finely pulverized. Boil the mixture in about twelve times as much water
as you took of Tartar. When the saline part of the Tartar is dissolved,
filter the liquor boiling-hot through a flannel bag, and then set it in
a cool place. In a very little time crystals of a russet colour will
shoot therein. Decant the liquor from these crystals; evaporate it to
a pellicle, and set it again to crystallize. Go on in this manner till
it will shoot no more. Collect all the Salt you have thus obtained, and
keep it under the name of _Chalybeated Tartar_.
To make the Tincture of Steel with Tartar, mix together six ounces of
clean Iron filings, and one pound of white Tartar in powder. Put this
mixture into a large iron kettle, and pour thereon as much rain-water
as will moisten it.
Make a paste of this matter, and leave it thus in a mass for
twenty-four hours. Then pour on it twelve pounds of rain-water,
and boil the whole for twelve hours at least, stirring the mixture
frequently, and adding from time to time some hot water, to supply the
place of what evaporates. When you have thus boiled the liquor, let it
stand quiet for some time, and then pour it off from the sediment at
bottom. Filter, and evaporate to the consistence of a syrup; and you
have the _Tincture of Mars with Tartar_. The Dispensatories generally
order an ounce of rectified Spirit of Wine to be poured on this
Tincture, in order to preserve it, and to keep it from growing mouldy,
as it is very apt to do.
_Soluble Chalybeated Tartar_ is prepared by mixing four ounces of
Tartarized Tartar, with one pound of the Tincture of Mars with Tartar,
and evaporating them together in an iron vessel to dryness; after which
it is kept in a well stopped phial, to prevent its growing moist in the
air.
_OBSERVATIONS._
The three preparations of this process are medicines very well known
and much used. There is even reason to think that those, who first
thought of combining Tartar in this manner with Iron, had it in their
view to prepare compositions useful in medicine, rather than merely to
produce new combinations for the improvement of Chymistry. Indeed, were
we to consider only the account here given of the manner in which these
three compositions are made, we should be inclined to think Crystal
of Tartar incapable of dissolving Iron so thoroughly and radically,
that, from the union of these two substances, a Neutral Metallic Salt
should arise, a Tartar neutralized and made soluble by Iron. For it
is very certain that the first of these preparations, which is called
Chalybeated Tartar, is nothing but the saline part of Tartar dissolved
by boiling water, and then precipitated and crystallized along with
particles of iron, that are reduced, at most, into a rust, or a
_crocus_ only, but have contracted no union with the crystal of Tartar,
which remains as Acid and as indissoluble after this preparation as
before. Accordingly it is called only _Chalybeated Tartar_, and not
_Soluble Chalybeated Tartar_: and, as this latter name hath been given
only to the Tartarized Tincture of Mars compounded with Tartarized
Tartar; that is, with Tartar rendered soluble by a Fixed Alkali, and
not by Iron; there is reason to presume, that the Tincture of Mars
alone was not thought worthy of being called a Soluble Chalybeated
Tartar; but that the name, importing _Tartar rendered soluble by Mars_,
belongs to that Tincture only when compounded with a true Soluble
Tartar.
It is nevertheless very certain, that the Tincture of Mars made with
Tartar contains a true Soluble Chalybeated Tartar; that is, a Neutral
Salt consisting of Crystal of Tartar united with Iron, and rendered
soluble by that union. The long boiling, necessary to prepare this
Tincture, gives the Acid of Tartar time to dissolve the Iron radically,
and to unite very closely therewith: but this is not the case in the
preparation of Chalybeated Tartar; to make which the Tartar is boiled
in water only as long as is necessary for the dissolution of its saline
parts; that is, about a quarter or half an hour; in which space the
Acid of the Tartar can scarce begin to act on the surface of the Iron:
for Acids have not so quick an effect on metals, as on Alkalis and
Absorbent Earths. Metallic substances, being vastly more compact, are
not near so soon dissolved by Acids, and especially by vegetable Acids,
weakened with heterogeneous matters, as the Acid of Tartar is.
I thought the dissolution of Iron by Tartar a point of sufficient
importance to deserve a little more attention than hath commonly been
given to it; and for that reason resolved to examine, and trace with
care, the phenomena observable in this operation.
As the crude Tartar, employed in making the Tartarized Tincture of
Mars, is replete with many oily and earthy parts, which cannot but
obstruct the dissolution of the Iron, and prevent our seeing clearly
how that dissolution is carried on, I thought it better to make use
of Cream, or Crystals, of Tartar, which, being pure and freed from
all those heterogeneous parts, dissolve in boiling water without
prejudicing its transparency.
I therefore pulverized Cream of Tartar, and dissolved as much thereof
in boiling water as it would take up. This solution I poured boiling
hot into a matrass, at the bottom of which I laid some fine iron wire
cut into small pieces. I set the matrass in a sand-bath; and having
heated it so as to make the liquor boil, I observed that, the instant
before it boiled, the liquor began to act very perceptibly upon the
Iron, in the same manner as other Acids act upon metallic substances;
that is, there appeared on the surfaces of the little bits of Iron
small bubbles, which immediately rose to the surface of the liquor,
and succeeded each other so fast, that they formed lines, or jets,
seemingly continued from the surface of the Iron to the surface of the
liquor, which, little by little, acquired a faint tinge of yellow.
When the liquor was heated so as to boil, the dissolution still went
on, but much more briskly, and the liquor acquired a deeper colour.
After boiling about an hour, the liquor, which at first was very clear,
became turbid, and of an opaque white; which made me think, that some
of the Cream of Tartar, dissolved therein, began to precipitate.
I let the whole boil some time longer, and the white precipitate
becoming more considerable, I resolved to filter the liquor, which
passed through clear, and tinged with a greenish yellow. There remained
on the filter a whitish sediment, which I found to be true Cream of
Tartar. The filtered liquor tasted much like a solution of Copperas.
I evaporated it in a glass bason, set in a sand-heat, but no pellicle
appeared; which made me conclude that it would produce no crystals:
accordingly, having taken some of it out of the bason, when it was
considerably reduced by evaporation, and set it in a cool place, no
crystal shot in it.
The rest of the liquor I evaporated to dryness: it left a blackish
brown residuum, which had the same taste with the liquor before
evaporation, but much stronger. This residuum melts very readily in
the mouth, without leaving on the tongue the least gritty particle.
Being exposed very dry to the air, it grows moist, and runs into a
liquor in a very little time. It dissolves easily and readily in a very
small quantity of cold water. This solution being mixed with Fixed
Alkalis, in various proportions, doth not grow turbid, nor drops any
precipitate; but with a decoction of galls it makes ink. Acids give it
a much clearer colour, and at first produce no precipitation; but, in a
quarter of an hour, there appears a precipitate much of the same colour
with the solution. This precipitate is no other than Cream of Tartar,
tinged of a russet colour by the liquor, which grows turbid, and a
little whitish, when the precipitate begins to form.
These experiments, and the circumstances attending them, will not
allow us to doubt the truth of what I advanced concerning the Tincture
of Mars made with Tartar, _viz._ that it is nothing but Crystal of
Tartar by which Iron is dissolved, and which is rendered soluble by
that metal. We see at the very first that Crystal of Tartar acts upon
Iron, just as other Acids do. Indeed this metallic solution is not
precipitated by Alkalis: but we know that Alkalis possess the property
of dissolving Iron, especially when the metal is previously divided by
an Acid; so that there is reason to think this may be the case, when an
Alkali is mixed with our Soluble Chalybeated Tartar.
As this Soluble Tartar is a saponaceous and oily Salt, it is also
possible that it may be dissolved entirely by the Alkali, without
suffering any decomposition; especially as Alkalis decompound Neutral
Metallic Salts, by means only of the stronger affinity which they
have with the Acids, than with the Metals, of which those Salts are
compounded. Now, as our Soluble Chalybeated Tartar is compounded of
that Metal which the Alkali dissolves with the greatest ease, and
of that Acid with which it hath the least affinity of any, it is
very possible that it may not have a greater affinity with the Acid
than with the metallic basis of this Salt, and so be uncapable of
decompounding it. However, as this Soluble Chalybeated Tartar makes
a black liquor with a decoction of Galls, and as nothing but Iron
dissolved by an Acid hath that property, it may be safely concluded,
that this Salt really consists of Iron dissolved by the Acid of Tartar.
The precipitate which a solution of this Salt lets fall, on the
addition of an Acid, is another proof that it consists of these two
principles: for this precipitate can be no other than the Tartarous
Acid, which, being the weakest of all Acids, is separated from the Iron
by the Acid added to the solution; which Acid unites with the Martial
basis, and forms another Neutral Metallic Salt, according to the Acid
employed. Lastly, the great solubility of the desiccated residuum of
the Tincture of Mars, made with Tartar, is a very strong and decisive
proof, that this residuum is no other than Iron dissolved by the Acid
of Tartar: for what else can it be? Nothing but Iron and Crystal of
Tartar is made use of in the operation; and neither of these two
substances singly is so soluble as this new body.
We know, moreover, that Crystal of Tartar, which itself is
indissoluble, forms a Soluble Tartar when combined with pure Absorbent
Earths, though these matters be still more indissoluble than it,
or rather, are not soluble at all. Hence it is very natural to
conclude, that our residuum is a Tartar rendered soluble by Iron.
This Chalybeated Tartar is even more soluble than any other sort
of Soluble Tartar; for it very readily grows moist in the air, and
runs wholly into a liquid; on which account it is not susceptible of
crystallization.
I return to one of the circumstances attending my experiment, which
it is proper I should account for; though I have hitherto only
mentioned it, without more particular notice, that I might not break
the connection between facts, and the consequences resulting from
them. The circumstance I mean is the precipitation of the Cream of
Tartar dissolved in the liquor, which, I said, happens when the saline
solution hath boiled upon the Iron about an hour. This precipitation
of the Cream of Tartar may be partly occasioned by the evaporation of
the water in which it is dissolved: for the water having taken up, as
was said, as much Cream of Tartar as it was capable of dissolving, when
the quantity of water comes to be lessened, a proportional quantity of
Cream of Tartar must precipitate.
But some other cause must also contribute to produce this
precipitation: for, as I boiled my liquor in a matrass, the evaporation
of the liquor could not be considerable, and yet the precipitate was
very copious. Moreover, I replenished the matrass with much more water
than was necessary to replace what had evaporated; yet I could not
re-dissolve the precipitated Cream of Tartar, nor even sensibly lessen
its quantity.
The true cause of this effect I take to be as follows. When the
solution of Cream of Tartar hath boiled for some time upon the Iron,
and dissolved a certain quantity thereof, a proportional quantity of
Soluble Chalybeated Tartar is formed. Now as this Salt is much more
soluble in water than Cream of Tartar, and as water always takes up
the more soluble Salts, preferably to the less soluble, it is not
surprising that Cream of Tartar, being one of those saline substances
which dissolve with the greatest difficulty, should on this occasion
separate from the liquor, and precipitate; yielding its place to a Salt
which hath a much greater affinity with water.
Hence it appears, that to re-dissolve the Cream of Tartar, and render
it capable of continuing to dissolve the iron as efficaciously as
before, it is not sufficient that fresh water be added; but the
solution of the Soluble Chalybeated Tartar already formed must be
entirely decanted, and fresh water poured on the residue; and then this
water, not being impregnated with any Soluble Chalybeated Tartar, will
be capable of re-dissolving the Cream of Tartar, and every thing will
go on as at the beginning of the operation, till the Cream of Tartar
come to precipitate again, for the same reason as before, and make a
repetition of the same management necessary. The liquor is far from
being saturated with Soluble Chalybeated Tartar, when the precipitation
of the Cream of Tartar renders it necessary to decant it: so that the
water must be often renewed, if you carry the operation to the utmost;
and then all these solutions must be added together, and evaporated,
either to dryness, if you desire to have the salt in a dry form, or to
any other degree you think proper.
This method I followed at first: but as it is exceeding long and
tedious, though perhaps the best; and as I wanted to have a moderate
quantity of Soluble Chalybeated Tartar, with less trouble, and in less
time, if possible, I resolved to try whether or no Cream of Tartar,
though separated from the liquor and undissolved, were still capable of
acting on the iron with such efficacy as to dissolve it. I therefore
continued to boil the tartarous solution on the filings of Iron,
notwithstanding the precipitation of the Cream of Tartar, taking care
only to add fresh water from time to time, as directed in the process
for the Tartarized Tincture of Mars, to replace what evaporated; and
I observed that, in fact, the Cream of Tartar, though not perfectly
dissolved, but only divided and agitated by the motion of boiling,
still continued to act upon the Iron; so that the liquor, after boiling
seven or eight hours, was so impregnated as to yield by evaporation a
reasonable quantity, in bulk, of Salt in a dry form.
PROCESS IV.
_Crystal of Tartar combined with the reguline Part of Antimony.
Stibiated or Emetic Tartar._
Pulverize and mix together equal parts of the Glass and of the Liver
of Antimony. Put this mixture, with the same quantity of pulverized
Cream of Tartar, into a vessel capable of containing as much water as
will dissolve the Cream of Tartar. Boil the whole for twelve hours,
from time to time adding warm water, to replace what is dissipated by
evaporation. Having thus boiled your liquor, filter it while boiling
hot; evaporate to dryness; and you will have a saline matter which is
_Emetic Tartar_.
_OBSERVATIONS._
The Glass and Liver of Antimony are no other, as was said in its place,
than the metallic earth of Antimony separated from the redundant
Sulphur of that mineral; but still retaining such a quantity of
phlogiston as to possess, excepting its metalline colour, nearly the
same properties with Regulus of Antimony, and especially its emetic
quality, and its solubility in Acids. Indeed these two preparations
seem to have more of an emetic quality than the Regulus itself, and
therefore are employed preferably to all others in the preparation of
Emetic Tartar.
It is not yet ascertained in which of the principles of Antimony its
emetic virtue resides. We are sure, however, that it cannot be ascribed
to its earthy part: for the calx of Antimony, when entirely deprived of
all phlogiston, is not emetic, nor even purgative; as is evident from
the effects of Diaphoretic Antimony and the Pearly Matter.
Some authors think Antimony contains an arsenical principle, to which
they impute its emetic quality; nor is their opinion altogether void of
probability. For this arsenical part seems to be indicated by several
of the properties of Antimony, and particularly by its affinities with
other metallic substances, in which it very nearly resembles Arsenic.
But this doth not amount to a positive proof: for we can draw nothing
but probable conjectures, at most, from such analogies.
Other Chymists think the emetic virtue of Antimony depends on the
union of its metallic earth with its phlogiston. This opinion seems
to me much more probable than the other: for by only recombining a
phlogiston with the earth of Antimony, deprived by calcination of all
its emetic virtue, that virtue is perfectly restored, and the Regulus
thus revivified is no less emetic than that which never underwent
calcination.
However this be, it is certain that Cream of Tartar acquires an
emetic quality, not by barely uniting with one of the principles of
Antimony, but by dissolving entirely the reguline, or semi-reguline,
part thereof; and that its emetic quality is so much the stronger, the
more of that substance it hath dissolved. This is the result of several
experiments made on the subject by Mr. Geoffroy.
That gentleman collected several parcels of Emetic Tartar, having
different degrees of strength. "I employed," says he[15], "an ounce of
each of those Emetic Tartars: I rubbed them separately with an equal
weight, or something more, of a black flux, made of two parts of red
Tartar, and one part of Nitre calcined together. These mixtures I put
into different crucibles, formed like inverted cones: I kept them in a
melting heat till the Salts in fusion sunk, and appeared like a smooth
oil at the bottom of each crucible. I then let the fire go out, broke
the crucibles when cold, and found the resuscitated Regulus in a mass
at bottom.
[15] Memoirs of the Academy for 1734, p. 421.
"Out of one ounce of the weakest Emetic Tartars I obtained from thirty
grains to one dram eighteen grains of Regulus. From one ounce of such
as were of a middling strength I got one dram and an half; and the most
violent yielded me two drams and ten grains.
"The power, therefore, of the strongest Emetic Tartars," continues he,
"depends on the quantity of Regulus of Antimony dissolved by the Cream
of Tartar, and the nearer the preparations of Antimony, on which the
solution of Cream of Tartar is boiled, are to the form of a Regulus or
a Glass, the more violent is the Emetic Tartar; because the Vegetable
Acid of the Tartar acts then more immediately upon the Emetic part of
the Antimony, and dissolves more of it."
Mr. Geoffroy found upon trial, that Cream of Tartar boiled for a due
time on Crude Antimony, doth indeed dissolve a little of the reguline
part thereof; but that the quantity of Regulus dissolved thereby is
so very small, that the Emetic Tartar produced is extremely weak. The
gross Sulphur, in this case, hinders the Cream of Tartar from acting
on the reguline part with so much efficacy, as when the Antimony is
properly prepared by freeing it entirely from its redundant Sulphur.
Nothing can be added to what Mr. Geoffroy hath said on this subject.
His experiments are decisive, and set the truth he intended to prove in
the clearest light.
Mr. Hoffman affirms, that Emetic Tartar loses part of its virtue by
being boiled too long. A very able Chymist goes so far as to say, that
Tartar ought not to boil above six or seven minutes with prepared
Antimony; because longer boiling destroys part of its Emetic quality.
Can this arise from hence, that Cream of Tartar, after dissolving
a certain quantity of the reguline substance, separates from it
afterwards? Or is the Cream of Tartar itself decomposed by too long
boiling? This deserves to be particularly inquired into, as well as the
nature of the Metallic Salt, which results from the union of the Acid
of Tartar with the Regulus of Antimony.
Crystal of Tartar acts also on several other metallic substances, and
particularly on Lead; with which it forms a Salt, resembling Tartarized
Tartar in the figure of its crystals.
CHAP. V.
_Of the_ PRODUCT _of_ ACETOUS FERMENTATION.
PROCESS I.
_Substances susceptible of the Acetous Fermentation turned into
Vinegar._
The Wine, the Cyder, or the Malt-liquor, which you intend to convert
into Vinegar, being first thoroughly mixed with its lees, and with the
Tartar it may have deposited, put your liquor into a vat used before,
either for making or for holding Vinegar. This vessel must not be quite
full, and the external air must have access to the liquor contained in
it. Set it where the air may have a degree of warmth answering nearly
to the twentieth degree above 0 in Mr. de Réaumur's Thermometer. Stir
the liquor from time to time. There will arise in it a new fermentative
motion, accompanied with heat: its vinous odour will gradually change,
and turn to a sour smell, which will become stronger and stronger,
till the fermentation be finished, and cease of itself. Then stop your
vessel close; the liquor it contains will be found converted into
Vinegar.
_OBSERVATIONS._
All substances that have undergone the spirituous fermentation are
capable of being changed into an Acid, by passing through this second
fermentation, or this second stage of fermentation. Spirituous liquors,
such as Wine, Cyder, Beer, being exposed to a hot air, grow sour in
a very short time. Nay, these liquors, though kept with all possible
care, in very close vessels, and in a cool place, degenerate at last,
change their natures, and insensibly turn sour. Thus the product of
spirituous fermentation naturally and spontaneously degenerates to an
Acid.
For this reason it is of great importance, in making Wine, or any
other vinous liquor, to stop the fermentation entirely, if you desire
the Wine should contain as much Spirit as possible. It is even more
advantageous to check the fermentation a little before it comes to the
height, than afterwards: because the fermentation, though slackened,
and in appearance totally ceased, still continues in the vessels; but
in a manner so much the less perceptible, as it proceeds more slowly.
Thus those liquors, in which the fermentation is not quite finished,
but checked, continue for some time to gain more Spirit: whereas, on
the contrary, they degenerate and gradually turn sour, if you let the
spirituous fermentation go on till it be entirely finished.
The production of the second fermentation, which we are now to
consider, is an Acid of so much the greater strength, the stronger and
more generous the spirituous liquor, in which it is excited, originally
was. The strength of this Acid, commonly called _Vinegar_, depends
likewise, in a great measure, on the methods used in fermenting the
vinous liquor, in order to convert it into Vinegar: for if it be
fermented in broad, flat vessels, and left to grow sour of itself, the
spirituous part will be dissipated, and the liquor, though sour indeed,
will be vapid and effete.
The Vinegar-makers, to increase the strength of their Vinegar, use
certain methods of which they make a mystery, keeping them very secret.
However, Mr. Boerhaave gives us, from some Authors, the following
description of a process for making Vinegar.
"Take two large oaken Vats or Hogsheads, and in each of these place a
wooden grate or hurdle, at the distance of a foot from the bottom. Set
the vessel upright, and on the grates place a moderately close layer
of green twigs, or fresh cuttings of the vine. Then fill up the vessel
with the foot-stalks of grapes, commonly called the _Rape_, to within a
foot of the top of the vessel, which must be left quite open.
"Having thus prepared the two vessels, pour into them the Wine to
be converted into Vinegar, so as to fill one of them quite up, and
the other but half full. Leave them thus for twenty-four hours, and
then fill up the half-filled vessel, with liquor from that which is
quite full, and which will now in its turn be left only half-full.
Four and twenty hours afterwards repeat the same operation, and thus
go on, keeping the vessels alternately full and half-full, during
every twenty-four hours, till the Vinegar be made. On the second or
third day there will arise, in the half-filled vessel, a fermentative
motion, accompanied with a sensible heat, which will gradually
increase from day to day. On the contrary, the fermenting motion is
almost imperceptible in the full vessel; and as the two vessels are
alternately full and half-full, the fermentation is by that means, in
some measure, interrupted, and is only renewed every other day, in each
vessel.
"When this motion appears to be entirely ceased, even in the
half-filled vessel, it is a sign that the fermentation is finished;
and therefore the vinegar is then to be put into common casks, close
stopped, and kept in a cool place.
"A greater or less degree of warmth accelerates or checks this, as
well as the spirituous fermentation. In France it is finished in
about fifteen days, during the summer; but if the heat of the air be
very great, and exceed the twenty-fifth degree of Mr. de Réaumur's
Thermometer, the half-filled vessel must be filled up every twelve
hours; because, if the fermentation be not so checked in that time,
it will become so violent, and the liquor will be so heated, that
many of the spirituous parts, on which the strength of the Vinegar
depends, will be dissipated; so that nothing will remain, after the
fermentation, but a vapid wash, sour indeed, but effete. The better to
prevent the dissipation of the spirituous parts, it is a proper and
usual precaution to close the mouth of the half-filled vessel, in which
the liquor ferments, with a cover made also of oak-wood. As to the full
vessel, it is always left open, that the air may act freely on the
liquor it contains: for it is not liable to the same inconveniencies,
because it ferments but very slowly."
The vine-cuttings and grape-stalks, which the Vinegar-makers put
into their vessels, serve to increase the strength of the liquor.
These matters contain a very manifest and perceptible Acid. They also
serve as a ferment; that is, they dispose the Wine to become eager
more expeditiously, and more vigorously. They are the better, and
the more efficacious, for having been once used, because they are
thereby thoroughly drenched with the fermented Acid: and therefore the
Vinegar-makers lay them by, for preparing other Vinegar, after washing
them nimbly in running water, in order to free them from a viscid oily
matter, which settles on them during the fermentation. This matter must
by all means be removed; because it is disposed to grow mouldy and rot;
so that it cannot but be prejudicial to any liquor into which you put
it.
As the Acetous fermentation differs from the Spirituous in its
production, so it doth in many circumstances attending it. 1. Motion
and agitation are not prejudicial to the Acetous fermentation, as they
are to the Spirituous; on the contrary, moderate stirring, provided
it be not continual, is of service to it. 2. This fermentation is
accompanied with remarkable heat; whereas, the warmth of the spirituous
fermentation is scarce sensible. 3. I do not believe there ever was an
instance of the vapour that rises from a liquor in Acetous fermentation
proving noxious, and producing either disorders or sudden death, as
the vapour of fermenting Wine doth. 4. Vinegar deposites a viscid oily
matter, as hath just been observed, very different from the Lees and
Tartar of Wine. Vinegar never deposites any Tartar; even though new
Wine, that hath not yet deposited its Tartar, should be used in making
it.
The following processes will give us occasion to treat of the nature of
Vinegar, and the principles of which it consists.
PROCESS II.
_To concentrate Vinegar by Frost._
Expose to the air, in frosty weather, the Vinegar you desire to
concentrate. Icicles will form in it; but the whole liquor will
not freeze. Take out those icicles: and if you desire a further
concentration of your Vinegar by this method, the liquor which did
not freeze the first time must be exposed to a stronger frost. More
icicles will form therein, which must likewise be separated, and kept
by themselves. The liquor which doth not freeze this second time will
be a very strong concentrated Vinegar.
_OBSERVATIONS._
Liquors, replete with an Acid, freeze with much more difficulty than
pure water. Thus, if a very aqueous acid liquor be exposed to frost,
some of the water in the liquor will presently freeze; while the rest,
being rendered more acid by the separation of the frozen phlegm, will
remain fluid, and resist the degree of cold which freezes water. Now
Vinegar, being an acid liquor containing much water, may therefore be
highly concentrated by freezing its phlegm in this manner; and the
more icicles you get from it, the stronger and more active will the
remaining Vinegar be.
Mr. Stahl was the first, I believe, who thus made use of congelation,
for procuring a very strong Acid of Vinegar. Mr. Geoffroy hath since
taken the same method. A curious and circumstantial account of his
experiments, on this subject, are printed in the Memoirs of the Academy
for 1739.
As it was excessive cold in the winter of that year, Mr. Geoffroy took
the opportunity of exposing to the frost several Vinegars of different
strengths; and he determined the degree of Acidity in each, both before
and after their concentration, in order to compare them, and discover
how much stronger each Vinegar was rendered by the freezing of the
aqueous part. To determine the strength of the Vinegars, he made use
of the method pointed out by Mr. Homberg and Mr. Stahl. This method
consists in combining to the exact point of saturation, a certain
quantity of Vinegar with well-dried Salt of Tartar. The more Salt of
Tartar is required, to absorb and perfectly neutralize the Vinegar, the
stronger it must be reckoned; because the quantity of Alkali necessary
to constitute a Neutral Salt is always proportioned to the quantity of
Acid in that Salt.
One of the Vinegars employed in Mr. Geoffroy's experiments, two drams
of which were entirely absorbed by six grains of Salt of Tartar, having
been concentrated by once freezing, and thereby reduced from eighteen
quarts to six, he found it so increased in strength, that two drams
thereof required twenty-four grains of Salt of Tartar to absorb them.
The first icicles that separate from Vinegar, in this process, are
perfectly clear, and as insipid as water. As the Vinegar becomes more
concentrated, the plates of ice becoming thinner, more spongy, and
flaky like snow, retain between them some portion of the Acid; and it
is proper to begin to save them as soon as they appear to be sensibly
acid.
Mr. Geoffroy carried the concentration of Vinegar as far as the cold
of that winter in 1739 would allow him; and eight quarts of Vinegar,
already concentrated by frost in the preceding years, being reduced to
two quarts and a half by the frost of the 19th of January, the coldest
day of that year, was found to be so strong, that two drams thereof
required forty-eight grains of Salt of Tartar to absorb them. The
icicles of this Vinegar, being thawed, retain so much strength as to
require thirteen grains of the Salt of Tartar to absorb them.
Vinegar suffers no decomposition by the congelation of its phlegm, and
the consequent concentration of its Acid. What is left still contains
all the principles of which Vinegar consists. Its principles are only
brought nearer together, and into a smaller compass: and for this
reason it grows the thicker the more it is concentrated. When therefore
you desire to concentrate the Acid of Vinegar, and at the same time to
purify it, that is, to free it from some of its oil and earth, you must
have recourse to distillation.
Wine, as well as Vinegar, may be concentrated by freezing. Mr. Stahl
exposed several sorts of Wine to the frost, and by that means separated
from them about two thirds, or three quarters, of almost pure phlegm.
The remainders of the Wines so concentrated were of a somewhat
thickish consistence. They were very strong, and kept for several
years without altering, in places where the free access of the air,
alternately cold and hot according to the seasons, would have soured,
or spoiled, any other kind of Wine in the space of a few weeks.
Wine thus concentrated by freezing is not thereby decomposed, any
more than Vinegar: it is only dephlegmated. By the addition of as
much water as was separated from it, you may restore it to its former
condition; in which respect it differs greatly from the residue of
Wine whose spirituous part, with a proportion of its phlegm, hath been
drawn off by distillation: for though you mix that residue again with
the principles you separated from it, you can never make Wine of it
again; the spirituous part being no longer in a capacity to combine
with the other principles of the Wine, in the same manner as before
that separation. And this shews that heat, besides separating the
most volatile parts, produces moreover a considerable change in the
disposition of those which did not rise in the first distillation.
Since the above experiments were made by Messrs. Stahl and Geoffroy,
concentration by freezing is pretty frequently practised in
laboratories; but on Vinegar only, seldom on Wine: because, when
Vinegar is thus concentrated, a much stronger Acid is more easily and
more expeditiously obtained from it, as will be shewn in the following
process; whereas the distillation, as well as the quality, of Spirit
of Wine is much the same, whether the Wine it is obtained from be
concentrated or no. The reason of this difference is, that Spirit
of Wine, being very light, rises in distillation before the phlegm;
whereas the Acid of Vinegar, being much more ponderous, rises only at
the same time with the aqueous part, or even after it.
PROCESS III.
_Vinegar analyzed by Distillation._
Into a glass or stone cucurbit put the Vinegar to be distilled; fit to
it a glass head; place your alembic in the sand-bath of a distilling
furnace, and lute on a receiver. Apply a very gentle heat at first. A
clear, limpid, light liquor will rise, and fall in distinct drops,
like water, from the nose of the alembic.
Continue distilling this first liquor, till the vinegar contained
in the cucurbit be diminished about a fourth part. Then shift your
receiver, and increase the fire a little. A clear liquor will still
come over, but heavier and more acid than the former. Distil in this
manner, till you have drawn off, into your second receiver, two-thirds
of the liquor that was left in the cucurbit.
A thick matter will now remain at the bottom of the still: put it
into a retort; lute on a receiver; set your retort in a reverberating
furnace, and distil with degrees of fire. There will come over a limpid
liquor, very acid and sharp, yet ponderous, and requiring a great
degree of fire to raise it; on which account it makes the receiver very
hot. It hath a strong empyreumatic smell. When the distillation begins
to slacken, increase your fire. There will rise an Oil of a fetid,
quick smell. At last, when nothing more will rise with the strongest
fire, break the retort, and in it you will find a black charred matter:
burn it, and from the ashes lixiviated with water you will obtain a
Fixed Alkali.
_OBSERVATIONS._
None of the liquors that come over in this operation, before the
last fetid Oil, seem to have any other properties than those of
an oily Acid; none of them is inflammable, none of them resembles
Spirit of Wine; but all of them being thrown into the fire extinguish
it. Mr. Boerhaave however takes notice, that a Chymist, named
Vigani, affirms the first portion of the liquor which rises in the
distillation of Vinegar to be inflammable, and no other than Spirit
of Wine. Mr. Boerhaave suspected that this might happen from Vigani's
having distilled Vinegar too newly made; and found upon trial that
Vinegar, being distilled soon after it was made, yielded at first
in distillation a certain quantity of an Ardent Spirit; but that
the same thing did not happen in the distillation of old Vinegar.
And this proves that fermentation hath the same effect on Vinegar
as on Wine; that is, that though the fermentation which produces
these liquors seems to be over in a certain time, when the violent
intestine commotion ceases, yet it still continues in the vessels for a
considerable time after, though it be imperceptible. Thus, the portion
of Ardent Spirit, obtained from some Vinegars, comes from a small
quantity of Wine, which still remains unchanged in these Vinegars,
not having had time enough to turn sour. For it is certain, from the
experiments of all other Chymists as well as Mr. Boerhaave, that
Vinegar, when old enough, yields no Ardent Spirit in distillation.
But though old and well-made Vinegar yields no Ardent Spirit in
distillation, we cannot thence conclude that it contains none. On the
contrary, there are experiments which demonstrate that some of the
Ardent Spirit, which was in the Wine before it was turned into Vinegar,
still remains; but probably so combined and blended with the acid part,
that it cannot be separated and rendered perceptible but by peculiar
processes.
Mr. Geoffroy obtained an Ardent Spirit from Vinegar, by distilling it
as soon as it was concentrated by freezing. "This spirit," says he[16],
"is the first liquor that rises. At first it hath only the same degree
of inflammability as brandy; but, when re-distilled in the _balneum
mariæ_, it fires gun-powder, like the best rectified Spirit of Wine:
with this difference, that our Spirit is impregnated with an oil of an
acrid taste and empyreumatic smell, which makes it yellow, and imparts
its odour to it. This Spirit, at least that which comes over first,
retains none of the Acid of the Vinegar; seeing it neither changes the
tincture of violets, nor effervesces with Salt of Tartar."
[16] Memoirs of the Academy for 1729.
Mr. Geoffroy observes, that, if Vinegar concentrated by freezing
be afterwards kept for several years, no Ardent Spirit will then
be obtained from it by distillation. And this confirms what we
said of unconcentrated Vinegar, and gives reason to think that the
Ardent Spirit obtained from Vinegar, either by distilling it after
concentration by freezing, or by other processes of which we shall
treat in the sequel, is foreign to the Vinegar, and is only found
therein, as was said above, because Vinegar contains a certain quantity
of Wine which hath not altered its nature. For the Spirit of Wine we
obtain from Vinegar doth not hinder our obtaining from it a great deal
of Acid, which being more ponderous rises after it. Mr. Geoffroy gives
the following account of the sequel of his analysis of Vinegar by
distillation.
"Continuing to distil in a _balneum mariæ_ the concentrated Vinegar,
of which I had employed four pounds two ounces, there was left, after
the distillation, a residuum of fourteen ounces; which could not rise,
because it was too thick. I found it covered with a saline crust, which
is the true Essential Salt of Vinegar, and not of the same nature with
Tartar: for Tartar of Wine is scentless; whereas the Salt of Vinegar
hath a pungent smell, being the Acid of Tartar subtilized by its union
with the Sulphureous parts. If a sand-bath be now used, instead of
the _balneum mariæ_, to carry on the distillation without burning the
matter, part of this Salt will be resolved, and yield the last Acid
Spirit, which is the strongest that can be obtained.
"After I had, by a sand-heat, extracted all the Acid Spirit that the
several residuums put together would yield, I found at the bottom
of the cucurbit a brown mass, of the consistence of a pretty solid
extract. Of this I put into a retort two pounds, together with six
pounds of sand well washed and very dry; and, applying a graduated
heat, I first obtained six ounces of an Acid Spirit, that smelt very
strong of the empyreuma, and was a little coloured with some portion
of oil; seven ounces of Spirit, having a volatile urinous smell, came
over next: at last the white vapours appeared more and more dense. A
volatile concrete Salt adhered to the sides of the ballon, and I found
four ounces of a thick fetid Oil floating on the Spirit. The concrete
volatile Salt, when collected, weighed two drams. The black matter
remaining in the bottom of the retort, being calcined and lixiviated,
yielded a fat alkaline Salt, which it is almost impossible to dry."
I have given this account of Mr. Geoffroy's analysis of Vinegar at
length, only because it differs in several respects from that described
in the process, which is Mr. Boerhaave's, as well as from those
delivered by several other Authors, who make no mention either of the
saline matter, which Mr. Geoffroy found on the residuum of Vinegar,
after its first distillation in the _balneum mariæ_, or of the volatile
urinous Spirit and Salt, which he obtained from that residuum.
These differences may arise either from the manner of distilling the
Vinegar, or from Mr. Geoffroy's Vinegar having been concentrated by
freezing, or rather from the quantity, and, above all, from the age of
the Vinegar, examined by those different Chymists.
The distillation of Vinegar serves not only to separate its Acid from
a considerable quantity of earth and oily parts, with which it is
entangled, but also to dephlegmate and concentrate it. Yet Mr. Lemeri
affirms, that Vinegar is not distilled with a view to dephlegmate it.
He condemns the common method of throwing away the first runnings as
useless phlegm, and saving only what comes off afterwards; having, he
says, observed, that the phlegm of Vinegar cannot be abstracted, like
that of many other acid liquors, and that what comes over first is
almost as sharp as what rises afterwards, be the fire applied at first
ever so small.
There is reason to think that Mr. Lemeri did not carefully enough
examine the strength of his Spirit of Vinegar, at the different stages
of his distillation: for Mr. Geoffroy, in the Memoir above cited,
gives an account of a distillation of Vinegar, the product whereof
he examined with care, having for that purpose divided it into five
different portions: and his experiments put it beyond all doubt, that
the first portions of Spirit of Vinegar are far from being so acid
as the last. This Vinegar was so strong before distillation, that it
required six grains of Salt of Tartar to absorb two drams of it. Two
drams of the first portion of his Spirit were absorbed by three grains
only of Salt of Tartar: the Acid of the second portion took five grains
to absorb it. (Each experiment was made with two drams of Vinegar).
The third portion was absorbed by ten grains; the fourth by thirteen,
and the fifth took no less than nineteen: which proves that Vinegar,
like most other Acids, may be concentrated by distilling off the most
aqueous part, which is lighter than the Acid.
There are therefore two ways of concentrating Vinegar, and separating
its most acid part, namely distillation and congelation. These
two methods may be successively applied to the same Vinegar, and
a very powerful Acid obtained by their concurrence. Mr. Geoffroy
having exposed to the frost, on the 19th of January 1739, the last
russet-coloured liquor, drawn from the residuum of distilled Vinegar,
found it so concentrated thereby, that it required sixty grains of Salt
of Tartar to absorb two drams of it.
CHAP. VI.
_The_ ACID _of_ VINEGAR _combined with different_ SUBSTANCES.
PROCESS I.
_The Acid of Vinegar combined with alkaline Substances. Foliated Salt
of Tartar, or Regenerated Tartar. Decomposition of that Salt_.
Into a glass cucurbit put some very pure and well-dried Salt of Tartar;
and pour on it some good distilled Vinegar, by little and little at
a time. An effervescence will arise. Pour on more Vinegar, till you
attain the point of saturation. Then fit a head to the cucurbit; set it
in a sand-bath; and having luted on a receiver, distil with a gentle
heat, and very slowly, till nothing remain but a dry matter. On this
residuum drop a little of the same Vinegar; and if any effervescence
appears, add more Vinegar till you attain the point of saturation, and
distil again as before. If you observe no effervescence, the operation
was rightly performed.
_OBSERVATIONS._
It is not easy to hit the exact point of saturation in preparing this
Neutral Salt; because the oily parts, with which the Acid of Vinegar is
loaded, hinder it from acting so briskly and readily as it would do,
if it were as pure as the Mineral Acids: and for this reason it often
happens, that, when we have nearly attained the point of saturation,
the addition of an Acid makes no sensible effervescence, though the
Alkali be not yet entirely saturated; which deceives the operator, and
makes him conclude erroneously that he hath attained the true point of
saturation.
But he easily perceives his mistake, when, after having separated from
this saline compound all its superfluous moisture by distillation,
he drops fresh Vinegar upon it: for then the Salts being more
concentrated, and consequently more active, produce an effervescence,
which would not have been sensible if this last portion of Acid,
instead of coming into immediate contact with the dried Alkali, could
not have mixed therewith till diffused through, and in a manner
suffocated by, that phlegm from which the Acid of the Vinegar, before
neutralized, was gradually separated by its combining with the Alkali;
that phlegm keeping in solution both the Neutral Salt already formed,
and the Alkali not yet saturated. And for this reason it is necessary
to try, after the first desiccation of this Salt, which is called
_Regenerated Tartar_, whether or no the just point of saturation hath
been attained.
It may also happen, that, though the point of saturation was exactly
hit at first, this compound Salt shall nevertheless, after desiccation,
effervesce with fresh Vinegar, and therefore not be in a perfectly
neutral state at that time. In this case the Salt must have been dried
by too violent a fire, and partly decompounded by an excess of heat
carrying off some of the Acid, which does not adhere very strongly
to the Alkali. This is one of the reasons why it is necessary that
Regenerated Tartar be desiccated with a very gentle heat.
From what hath been said, concerning the desiccation of this Neutral
Salt, it is plain, that the use of it is only to free the Salt from
the great quantity of superfluous moisture wherein it is dissolved:
which proves that the Acid of Vinegar, like all other Acids dissolved
in much water, is separated from most of this redundant phlegm by being
combined with a Fixed Alkali. And hence we must conclude, that the
Acid of Vinegar, contained in Regenerated Tartar desiccated, is vastly
stronger and more concentrated than it was before: and accordingly Mr.
Geoffroy, having decompounded this Salt, by the means of concentrated
Oil of Vitriol, obtained a Spirit of Vinegar in white vapours, which
was very volatile and very strong, but perhaps somewhat depraved with a
taint of the Vitriolic Acid.
Though the Acid of Vinegar be freed, by combining with a Fixed Alkali,
from a great quantity of superfluous phlegm, as was shewn above; yet
the oily parts with which it is entangled still cleave to it: these
parts are not separated from it by its conversion into a Neutral Salt,
but, without quitting it, combine also with the Fixed Alkali; and this
gives Regenerated Tartar a saponaceous quality, and several other
peculiar properties.
Regenerated Tartar, when dried, is of a brown colour. It is
semi-volatile; melts with a very gentle heat, and then resembles an
unctuous liquor; which indicates its containing an Oil: when cast upon
live coals it flames; and, when distilled with a strong heat, yields an
actual oil; all which evidently prove the existence of that Oil.
This Salt is soluble in Spirit of Wine; a quality which it probably
owes also to its Oil. It requires about six parts of Spirit of Wine
to dissolve it; and the dissolution succeeds very well in a matrass,
with the help of a gentle warmth. If the Spirit of Wine be abstracted
from this solution, by distilling with a small fire, the Salt remains
at the bottom of the cucurbit, in the form of a dry substance composed
of leaves lying one upon another; which hath procured it the name of
_Terra Foliata Tartari_, or _Foliated Salt of Tartar_.
It is not absolutely necessary that Regenerated Tartar be dissolved in
Spirit of Wine to make the Foliated Salt: for it may be procured in
this form, by only evaporating the water in which it is dissolved. But
the operation succeeds better with Spirit of Wine; probably because the
success thereof depends on using an exceeding gentle warmth: now Spirit
of Wine evaporates with much less heat than water.
Regenerated Tartar may also be crystallized. If you desire to have
it in this form, combine the Acid with the Alkali to the point of
saturation; evaporate the liquor slowly to the consistence of a syrop,
and set it in a cool place; where it will shoot into clusters of
crystals lying one upon another like feathers.
Vinegar perfectly dissolves absorbent matters also, and particularly
those of the animal kingdom; such as Coral, Crabs-eyes, Pearls, &c. In
order to a dissolution of such matters, you must pulverize them, put
them into a matrass, and pour on them Spirit of Vinegar to the depth of
four fingers breadth: an effervescence will arise: when that is over,
set the mixture to digest two or three days in a sand-bath; then decant
the liquor, filter it, and evaporate it to dryness with a very gentle
heat. The matter which remains is called _Salt of Coral_, _of Pearls_,
_of Crabs-eyes_, _&c._ according to the substances dissolved. If,
instead of evaporating the liquor, a Fixed Alkali be mixed therewith,
the absorbent matter, that was dissolved by the Acid, will precipitate
in the form of a white powder, which is called the _Magistery of
Coral_, _of Pearls_, _&c._
PROCESS II.
_The Acid of Vinegar combined with Copper. Verdegris. Crystals of
Copper. This combination decompounded. Spirit of Verdegris._
Into a large matrass put Verdegris in powder. Pour on it distilled
Vinegar to the depth of four fingers breadth. Set the matrass in a
moderate sand-heat, and leave the whole in digestion, shaking it from
time to time. The Vinegar will acquire a very deep blue-green colour.
When the liquor is sufficiently coloured, pour it off by inclination.
Put some fresh Vinegar into the matrass; digest as before; and decant
the liquor again when it is sufficiently coloured. Proceed in this
manner till the Vinegar will extract no more colour. There will remain
in the matrass a considerable quantity of undissolved matter. The
Vinegar thus impregnated with Verdegris is called _Tincture of Copper_.
Mix these several Tinctures, and evaporate them with a gentle heat to
a pellicle. Then set the liquor in a cool place: in the space of a few
days a great many crystals of a most beautiful green colour will shoot
therein, and stick to the sides of the vessel. Pour off the liquor
from the crystals; evaporate it again to a pellicle, and set it by to
crystallize. Continue these evaporations and crystallizations, till no
more crystals will shoot in the liquor. These are called _Crystals of
Copper_, and are used in painting. To this combination of the Acid of
Vinegar with Copper the painters and dealers have given the title of
_Distilled Verdigris_.
_OBSERVATIONS._
Verdegris is prepared at Montpelier. To make it they take very clean
plates of Copper, which they lay, one over another, with husks of
grapes between, and after a certain time take them out. Their surfaces
are then covered all over with a very beautiful green crust, which
is _Verdegris_. This Verdegris is nothing but Copper corroded by the
Acid of Tartar, analagous to the Acid of Vinegar, which abounds in the
Wines of Languedoc, and especially in the rape, husks, and stones of
grapes that have a very austere taste. Verdegris is a sort of rust of
Copper; or Copper corroded and opened by the Acid of Wine, but not yet
converted intirely into a Neutral Salt: for it is not soluble in water,
nor does it crystallize. This arises from its not being united with a
sufficient quantity of Acid. The design of the operation here described
is to furnish the Verdegris with the quantity of Acid requisite to make
it a true Metallic Salt: for which purpose distilled Vinegar is very
fit.
Crystals of Copper may be obtained, without employing Verdegris,
by making use of Copper itself dissolved by the Acid of Vinegar,
according to the method practised with respect to Lead, as shall
be shewn hereafter. But Verdegris is generally used, because it
dissolves soonest; it being a Copper already half-dissolved by an Acid
correspondent to that of Vinegar.
Crystals of Copper are decompounded by the action of fire alone,
without any additament; because the Acid of Vinegar adheres but loosely
to Copper. In order to decompound this Salt and extract its Acid, it
must be put into a retort, and distilled in a reverbatory furnace with
degrees of fire. An insipid phlegm rises first, which is the water
retained by the Salt in crystallizing. This phlegm is succeeded by
an acid liquor, which rises in the form of white vapours that fill
the receiver. Towards the end of the distillation the fire must be
violently urged, in order to raise the strongest and most fixed Acid.
At last there remains in the retort a black matter, which is nothing
but Copper, that may be reduced by melting it in a crucible with one
part of Salt-petre and two parts of Tartar. A similar Acid, but more
oily, and in a much smaller quantity, may be obtained from Verdegris by
distillation.
The Acid, which in this distillation comes over after the first phlegm,
is an exceeding strong and concentrated Vinegar. It is known by the
title of _Spirit of Verdegris_. Zwelfer, and after him M. le Fevre in
his Chymistry, bestows extraordinary praises on this Spirit; pretending
that it will produce the Salt of Coral, and others of the same kind,
without losing any of its virtue, or ceasing to be acid; so as to
remain still capable of performing other operations of the same nature.
But Mr. Boerhaave and Mr. Lemeri positively deny the fact; and with
good reason, having formed their judgments on their own experiments.
Yet I can hardly think both Zwelfer and le Fevre would have affirmed a
thing of this nature, in such a positive and confident manner, if they
had been convinced in their minds that it was false. We must suppose
that those Chymists examined the matter with too little attention,
and were misled by some fallacious appearance. Probably they may have
compared this concentrated Vinegar with common distilled Vinegar;
they may have put to their Coral an equal dose thereof; and, after
saturation, they may have distilled off the superfluous liquor, which
may have effervesced with fresh Coral and dissolved it. Surprised at
this effect, they may have imagined that their Acid had lost none of
its strength, and that it had the virtue of converting into Salt any
quantity of Coral, or such other matters, without any prejudice to its
Acidity. A rash conclusion: which certainly they never would have made,
if they had carried the experiment far enough; if they had dissolved a
third or a fourth quantity of Coral in their Vinegar: for they would
have been thereby convinced that the Spirit of Verdegris, like all
other acid Spirits, deposites and leaves its Acid in absorbent matters;
and that if the liquor, which they drew off by distillation from
their first Salt of Coral, was still acid, and capable of dissolving
fresh Coral, nothing could be inferred from thence but that Spirit
of Verdegris is an exceedingly concentrated Vinegar, which, in the
same quantity of liquor, contains much more Acid than the strongest
distilled Vinegar prepared in the common way; that therefore a much
smaller dose thereof is required to convert a given quantity of Coral
into Salt; and that the liquor, which they distilled from their first
Salt, still retained some of its virtue, only because it was replete
with much more Acid than could be neutralized by the Coral. But a
love of the marvellous so prepossesses the mind of man, that it often
hinders him from perceiving the most obvious facts. This is the fault
of all the ancient Chymists in general: and I believe the only reason
why we find their books stuffed with so many unsucceeding experiments
was, that their heated imaginations frequently represented things to
them otherwise than they really were.
PROCESS III.
_The Acid of Vinegar combined with Lead. Ceruse. Salt or Sugar of Lead.
This combination decompounded._
Into the glass head of a cucurbit, put thin plates of Lead, and secure
them so that they may not fall out when the head is put upon the
cucurbit. Fit on this head to a wide-mouthed cucurbit containing some
Vinegar. Set it in a sand-bath; lute on a receiver, and distil with a
gentle heat for ten or twelve hours. Then take off the head: in it you
will find the leaden plates covered, and, in a manner, crusted over
with a white matter. This being brushed off with a hare's foot is what
we call _Ceruse_. The leaden plates thus cleansed may be employed again
for the same purpose, till they be wholly converted into Ceruse by
repeated distillations. During the operation there will come over into
the receiver a liquor somewhat turbid and whitish. This is a distilled
Vinegar in which some Lead is dissolved.
Reduce a quantity of Ceruse into powder; put it into a matrass; pour on
it twelve or fifteen times as much distilled Vinegar; set the matrass
in a sand-bath; leave the matter in digestion for a day, shaking it
from time to time: then decant your liquor, and keep it apart. Pour
fresh Vinegar on what is left in the matrass, and digest as before.
Proceed thus till you have dissolved one half, or two thirds, of the
Ceruse.
Evaporate to a pellicle the liquors you poured off from the Ceruse, and
set them in a cool place. Greyish crystals will shoot therein. Decant
the liquor from the crystals; evaporate it again to a pellicle, and set
it by to crystallize. Proceed thus evaporating and crystallizing, as
long as any crystals will shoot. Dissolve your crystals in distilled
Vinegar, and evaporate the solution, which will then shoot into whiter
and purer crystals. This is the _Salt_ or _Sugar of Lead_.
_OBSERVATIONS._
Lead is easily dissolved by the Acid of Vinegar. If it be barely
exposed to the vapour of that Acid, its surface is corroded, and
converted into a kind of calx or white rust, much used in painting, and
known by the name of _Ceruse_ or _White Lead_. But this preparation of
Lead is not combined with a sufficient quantity of Acid to convert it
into a Salt: it is no more than lead divided and opened by the Acid of
Vinegar; a matter which is to Lead what Verdegris is to Copper. And
therefore if you desire to combine Ceruse with the quantity of Acid
necessary to convert it into a true Neutral Salt, you must treat it
in the same manner as we did Verdegris, in order to procure Crystals
of Copper; that is, you must dissolve it in distilled Vinegar, as the
process directs.
The Salt of Lead is not very white when it first shoots; and for this
reason it is dissolved again in distilled Vinegar, and crystallized
a second time. If salt of Lead be repeatedly dissolved in distilled
Vinegar, and the liquor evaporated, it will grow thick; but cannot be
desiccated without great difficulty. If the same operation be oftener
repeated, this quality will be thereby more and more increased; till
at last it will remain on the fire like an Oil, or melted Wax: it
coagulates as it cools, and then looks, at first sight, like a metallic
mass, somewhat resembling Silver. This matter runs with a very gentle
heat, almost as easily as wax.