Experiments and Considerations Touching Colours (1664) by Robert Boyle

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_Annotation._

This Experiment may bring some Light to, and receive some from a couple of
other Experiments, that I remember I have met with in the ingenious
_Gassendus_'s Animadversions upon _Epicurus_'s Philosophy, whilst I was
turning over the Leaves of those Learned Commentaries; (my Eyes being too
weak to let me read such Voluminous Books quite thorough) And I the less
scruple (notwithstanding my contrary Custom in this Treatise) to set down
these Experiments of another, because I shall a little improve the latter
of them, and because by comparing there with that which I have last
recited, we may be assisted to Conjecture upon what account it is, that Oyl
of Vitriol heightens the Tincture of Red-rose Leaves, since Spirit of Salt,
which is a highly Acid _Menstruum_, but otherwise differing enough from Oyl
of Vitriol, does the same thing. Our Authors Experiments then, as we made
them, are these; We took about a Glass-full of luke-warm Water, and in it
immerg'd a quantity of the Leaves of _Senna_, and presently upon the
Immersion there did not appear any Redness in the Water, but dropping into
it a little Oyl of Tartar, the Liquor soon discover'd a Redness to the
watchfull Eye, whereas by a little of that Acid Liquor of Vitriol, which is
like the former, undeservedly called Oyl, such a Colour would not be
extracted from the infused _Senna_. On the other side we took some Red-rose
Leaves dry'd, and having shaken them into a Glass of fair Water, they
imparted to it no Redness, but upon the affusion of a little Oyl of Vitriol
the Water was immediately turn'd Red, which it would not have been, if
instead of Oyl of Vitriol, we had imployed Oyl of Tartar to produce that
Colour: That these were _Gassendus_ his Experiments, I partly remember, and
was assur'd by a Friend, who lately Transcribed them out of _Gassendus_ his
Book, which I therefore add, because I have not now that Book at hand. And
the design of _Gassendus_ in these Experiments our Friend affirms to be, to
prove, that of things not Red a Redness may be made only by Mixture, and
the Varied position of parts, wherein the Doctrine of that Subtil
Philosopher doth not a little Authorize, what we have formerly delivered
concerning the Emergency and Change of Colours. But the instances, that we
have out of him set down, seem not to be the most Eminent, that may be
produced of this truth: For our next Experiment will shew the production of
several Colours out of Liquors, which have not any of them any such Colour,
nor indeed any discernable one at all; and whereas though our Author tells
us, that there was no Redness either in the Water, or the Leaves of
_Senna_, or the Oyl of Tartar; And though it be true, that the Predominant
Colour of the Leaves of _Senna_ be another than Red, yet we have try'd,
that by steeping that Plant a Night even in Cold water, it would afford a
very deep Yellow or Reddish Tincture without the help of the Oyl of Tartar,
which seems to do little more than assist the Water to extract more nimbly
a plenty of that Red Tincture, wherewith the Leaves of _Senna_ do of
themselves abound, and having taken off the Tincture of _Senna_, made only
with fair Water, before it grew to be Reddish, and Decanted it from the
Leaves, we could not perceive, that by dropping some Oyl of Tartar into it,
that Colour was considerable, though it were a little heightned into a
Redness; which might have been expected, if the particles of the Oyl did
eminently Co-operate, otherwise than we have expressed, to the production
of this Redness.

And as for the Experiment with Red-rose Leaves, the same thing may be
alleged, for we found that such Leaves by bare Infusion for a Night and Day
in fair Water, did afford us a Tincture bordering at least upon Redness,
and that Colour being conspicuous in the Leaves themselves, would not by
some seem so much to be produc'd as to be extracted by the affusion of Oyl
of Vitriol. And the Experiment try'd with the dry'd Leaves of Damask-roses
succeeded but imperfectly, but that is indeed observable to our Authors
purpose, that Oyl of Tartar will not perform in this Experiment what Oyl of
Vitriol doth; but because this last named Liquor is not so easily to be
had, give me leave to Advertise you, that the Experiment will succeed, if
instead of it you imploy _Aqua-fortis_. And though some Trials of our own
formerly made, and others easily deducible from what we have already
deliver'd, about the different Families and Operations of Salt, might
enable us to present you an Experiment upon Red-rose Leaves, more
accommodated to our Authors purpose, than that which he hath given us; yet
our Reverence to so Candid a Philosopher, invites us rather to improve his
Experiment, than substitute another in its place. Take therefore of the
Tincture of Red-rose Leaves, (for with Damask-rose Leaves the Experiment
succeedeth not well) made as before hath been taught with a little Oyl of
Vitriol, and a good quantity of fair Water, pour off this Liquor into a
clear Vial, half fill'd with Limpid water; till the Water held against the
Light have acquir'd a competent Redness, without losing its Transparency,
into this Tincture drop leisurely a little good Spirit of Urine, and
shaking the Vial, which you must still hold against the Light, you shall
see the Red Liquor immediately turn'd into a fine Greenish Blew, which
Colour was not to be found in any of the Bodies, upon whose Mixture it
emerg'd, and this Change is the more observable, because in many Bodies the
Degenerating of Blew into Red is usual enough, but the turning of Red into
Blew is very unfrequent. If at every drop of Spirit of Urine you shake the
Vial containing the Red Tincture, you may delightfully observe a pretty
variety of Colours in the passage of that Tincture from a Red to a Blew,
and sometimes we have this way hit upon such a Liquor, as being look't upon
against and from the Light, did seem faintly to emulate the above-mention'd
Tincture of _Lignum Nephriticum_. And if you make the Tincture of Red-roses
very high, and without Diluting it with fair Water, pour on the Spirit of
Urine, you may have a Blew so deep, as to make the Liquor Opacous, but
being dropt upon White Paper the Colour will soon disclose it self. Also
having made the Red, and consequently the Blew Tincture very Transparent,
and suffer'd it to rest in a small open Vial for a Day or two, we found
according to our Conjecture, that not only the Blew but the Red Colour also
was Vanish'd; the clear Liquor being of a bright Amber Colour, at the
bottom of which subsided a Light, but Copious feculency of almost the same
Colour, which seems to be nothing but the Tincted parts of the Rose Leaves
drawn out by the Acid Spirits of the Oyl of Vitriol, and Precipitated by
the Volatile Salt of the Spirit of Urine, which makes it the more probable,
that the Redness drawn by the Oyl of Vitriol, was at least as well an
extraction of the Tinging parts of the Roses, as a production of Redness;
and lastly, if you be destitute of Spirit of Urine, you may change the
Colour of the Tincture of Roses with many other Sulphureous Salts, as a
strong Solution of Pot-ashes, Oyl of Tartar, &c. which yet are seldome so
free from Feculency, as the Spirituous parts of Urine becomes by repeated
Distillation.

_Annotation_.

On this, occasion, I call to mind, that I found, a way of producing, though
not the same kind of Blew, as I have been mentioning, yet a Colour near of
Kin to it, namely, a fair Purple, by imploying a Liquor not made Red by
Art, instead of the Tincture of Red-roses, made with an Acid Spirit; And my
way was only to take Log-wood, (a Wood very well known to Dyers) having by
Infusion the Powder of it a while in fair Water made that Liquor Red, I
dropt into it a _Tantillum_ of an Urinous Spirit, as that of Sal-Armoniack,
(and I have done the same thing with an _Alcali_) by which the Colour was
in a moment turn'd into a Rich, and lovely Purple. But care must be had,
that you let not fall into a Spoonfull above two or three Drops, lest the
Colour become so deep, as to make the Liquor too Opacous. And (to answer
the other part of _Gassendus_ his Experiment) if instead of fair Water, I
infus'd the Log-wood in Water made somewhat sowr by the Acid Spirit of
Salt, I should obtain neither a Purple Liquor, nor a Red, but only a Yellow
one.

_EXPERIMENT XL._

The Experiment I am now to mention to you, _Pyrophilus_, is that which both
you, and all the other _Virtuosi_ that have seen it, have been pleas'd to
think very strange; and indeed of all the Experiments of Colours, I have
yet met with, it seems to be the fittest to recommend the Doctrine propos'd
in this Treatise, and to shew that we need not suppose, that all Colours
must necessarily be Inherent Qualities, flowing from the Substantial Forms
of the Bodies they are said to belong to, since by a bare Mechanical change
of Texture in the Minute parts of Bodies; two Colours may in a moment be
Generated quite _De novo,_ and utterly Destroy'd. For there is this
difference betwixt the following Experiment, and most of the others
deliver'd in these Papers, that in this, the Colour that a Body already
had, is not chang'd into another, but betwixt two Bodies, each of them
apart devoid of Colour, there is in a moment generated a very deep Colour,
and which if it were let alone, would be permanent; and yet by a very small
Parcel of a third Body, that has no Colour of its own, (lest some may
pretend I know not what Antipathy betwixt Colours) this otherwise permanent
Colour will be in another trice so quite Destroy'd, that there will remain
no foot-stepts either of it or of any other Colour in the whole Mixture.

The Experiment is very easie, and it is thus perform'd: Take good common
Sublimate, and fully satiate with it what quantity of Water you please,
Filtre the Solution carefully through clean and close Paper, that it may
drop down as Clear and Colourless as Fountain water. Then when you'l shew
the Experiment, put of it about a Spoonfull into a small Wine-glass, or any
other convenient Vessel made of clear Glass, and droping in three or four
drops of good Oyl of Tartar, _per Deliquium_; well Filtred that it may
likewise be without Colour, these two Limpid Liquors will in the twinkling
of an Eye turn into an Opacous mixture of a deep Orange Colour, which by
keeping the Glass continually shaking in your hand, you must preserve from
setling too soon to the Bottom; And when the Spectators have a little
beheld this first Change, then you must presently drop in about four or
five drops of Oyl of Vitriol, and continuing to shake the Glass pretty
strongly, that it may the Nimbler diffuse it self, the whole Colour, if you
have gone Skilfully to work, will immediately disappear, and all the Liquor
in the Glass will be Clear and Colourless as before, without so much as a
Sediment at the Bottom. But for the more gracefull Trial of this
Experiment, 'twill not be amiss to observe, First, That there should not be
taken too much of the Solution of Sublimate, nor too much of the Oyl of
Tartar drop'd in, to avoid the necessity of putting in so much Oyl of
Vitriol as may make an Ebullition, and perhaps run over the Glass.
Secondly, That 'tis convenient to keep the Glass always a little shaking,
both for the better mixing of the Liquors, and to keep the Yellow Substance
from Subsiding, which else it would in a short time do, though when 'tis
subsided it will retain its Colour, and also be capable of being depriv'd
of it by the Oyl newly mention'd. Thirdly, That if any Yellow matter stick
at the sides of the Glass, 'tis but inclining the Glass, till the clarify'd
Liquor can wash alongst it, and the Liquor will presently imbibe it, and
deprive it of its Colour.

Many have somewhat wondred, how I came to light upon this Experiment, but
the Notions or Conjectures I have about the differing Natures of the
Several Tribes of Salts, having led me to devise the Experiment, it will
not be difficult for me to give you the Chymical Reason, if I may so speak,
of the _Phaenomenon_. Having then observ'd, that _Mercury_ being dissolv'd
in Some _Menstruums_, would yield a dark Yellow Precipitate, and supposing
that, as to this, common Water, and the Salts that stick to the _Mercury_
would be equivalent to those Acid _Menstruums_, which work upon the
_Quick-silver_, upon the account of their Saline particles, I substituted a
Solution of Sublimate in fair Water, instead of a Solution of _Mercury_ in
_Aqua-fortis_, or Spirit of _Nitre_, that simple Solution being both
clearer and free from that very offensive Smell, which accompanies the
Solutions of _Mercury_ made with those other corrosive Liquors; then I
consider'd, that That, which makes the Yellow Colour, is indeed but a
Precipitate made by the means of the Oyl of Tartar, which we drop in, and
which, as _Chymists_ know, does generally precipitate Metalline Bodies
corroded by Acid Salts; so that the Colour in our case results from the
Coalition of the Mercurial particles with the Saline ones, wherewith they
were formerly associated, and with the Alcalizate particles of the Salt of
Tartar that swim up and down in the Oyl. Wherefore considering also, that
very many of the effects of Lixiviate Liquors, upon the Solutions of other
Bodies, may be destroy'd by Acid _Menstruums_, as I elsewhere more
particularly declare, I concluded, that if I chose a very potently Acid
Liquor, which by its Incisive power might undo the work of the Oyl of
Tartar, and disperse again those Particles, which the other had by
Precipitation associated, into such minute Corpuscles as were before singly
Inconspicuous, they would become Inconspicuous again, and consequently
leave the Liquor as Colourless as before the Precipitation was made.

This, as I said, _Pyrophilus_, seems to be the Chymical reason of this
Experiment, that is such a reason, as, supposing the truth of those
Chymical Notions I have elsewhere I hope evinc'd, may give such an account
of the _Phaenomena_ as Chymical Notions can supply us with; but I both here
and elsewhere make use of this way of speaking, to intimate that I am
sufficiently aware of the difference betwixt a Chymical Explication of a
_Phaenomenon_, and one that is truly Philosophical or Mechanical; as in our
present case, I tell you something, when I tell you that the Yellowness of
the Mercurial Solution and the Oyl of Tartar is produc'd by the
Precipitation occasion'd by the affusion of the latter of those Liquors,
and that the destruction of the Colour proceeds from the Dissipation of
that Curdl'd matter, whose Texture is destroy'd, and which is dissolv'd
into Minute and Invisible particles by the potently Acid _Menstruum_, which
is the reason, why there remains no Sediment in the Bottom, because the
infused Oyl takes it up, and resolves it into hidden or invisible Parts, as
Water does Salt or Sugar. But when I have told you all this, I am far from
thinking I have told all that such an Inquisitive Person as your self would
know, for I presume you would desire as well as I to learn (at least) why
the Particles of the _Mercury_, of the Tartar, and of the Acid Salts
convening together, should make rather an Orange Colour than a Red, or a
Blew, or a Green, for 'tis not enough to say what I related a little
before, that divers Mercurial Solutions, though otherwise made, would yield
a Yellow precipitate, because the Question will recurr concerning them; and
to give it a satisfactory answer, is, I freely acknowledge, more than I
dare as yet pretend to.

But to confirm my conjecture about the Chymical reason of our Experiment, I
may add, that as I have (_viz._ pag. 34th. of this Treatise) elsewhere (on
another occasion) told you, with Saline Liquors of another kind and nature
than Salt of Tartar, (namely, with Spirit of Urine, and Liquors of kin to
that) I can make the _Mercury_ precipitate out of the first simple Solution
quite of another Colour than that hitherto mention'd; Nay, if instead of
altering the Precipitating liquor, I alter'd the Texture of the Sublimate
in such a way as my Notions about Salt requir'd, I could produce the same
_Phaenomenon_. For having purposely Sublim'd together Equal parts (or
thereabout) of Sal-Armoniack and Sublimate, first diligently Mix'd, the
ascending Flowers being diffolv'd in fair Water, and Filtred, gave a
Solution Limpid and Colourless, like that of the other Sublimates, and yet
an _Akaly_ drop'd into this Liquor did not turn it Yellow but White. And
upon the same Grounds we may with _Quick-silver_, without the help of
common Sublimate, prepare another sort of Flowers dissoluble in Water
without Discolouring it, with which I could likewise do what I newly
mention'd; to which I shall add, (what possibly you'l somewhat wonder at)
That so much does the Colour depend upon the Texture resulting from the
Convention of the several sorts of Corpuscles, that though in out
Experiment, Oyl of Vitriol destroys the Yellow Colour, yet with
_Quick-silver_ and fair Water, by the help of Oyl of Vitriol alone, we may
easily make a kind of Precipitate of a fair and permanent Yellow, as you
will e're long (in the forty second Expement of this third Part) be taught.
And I may further add, that I chose Oyl of Vitriol, not so much for any
other or peculiar Quality, as for its being, when 'tis well rectify'd,
(which 'tis somewhat hazardous to bring it to be) not only devoid of Colour
and in Smells, but extremely Strong and Incisive; For though common and
undephlegmated _Aqua-fortis_ will not perform the same thing well, yet that
which is made exceeding Strong by being carefully Dephlegm'd, will do it
pretty well, though not so well as Oyl of Vitriol which is so Strong, that
even without Rectification it may for a need be made use of. I will not
here tell you what I have try'd, that I may be able to deprive at pleasure
the Precipitate that one of the Sulphureous Liquors had made, by the
copious Affusion of the other: Because I found, though this Experiment is
too ticklish to let me give a full account of it in few words, I shall
therefore tell you, that it is not only for once, that the other
above-mention'd Experiment may be made, the same Numerical parcels of
Liquor being still imploy'd in it; for after I have Clarify'd the Orange
Colour'd Liquor, by the addition of as little of the Oyl of Viriol as will
suffice to perform the effect, I can again at pleasure re-produce the
Opacous Colour, by the dropping in of fresh Oyl of Tartar, and destroy it
again by the Re-affusion of more of the Acid _Menstruum_; and yet oftner if
I please, can I with these two contrariant Liquors recall and disperse the
Colour, though by reason of the addition of so much new Liquor, in
reference to the Mercurial particles, the Colour will at length appear more
dilute and faint.

_An improvement of the fortieth Experiment_.

And, _Pyrophilus_, to confirm yet further the Notions that led me to think
on the propos'd Experiment, I shall acquaint you with another, which when I
had conveniency I have sometimes added to it, and which has to the
Spectators appear'd little less Odd than the first; And though because the
Liquor, requisite to make the Trial succeed well, must be on purpose
prepar'd anew a while before, because it will not long retain its fitness
for this work, I do but seldome annex this Experiment to the other, yet I
shall tell you how I devis'd it, and how I make it. If you boyl Crude
Antimony in a strong and clear _Lixivium_, you shall separate a Substance
from it, which some Modern _Chymists_ are pleas'd to call its Sulphur, but
how deservedly I shall not here examine, having elsewhere done it in an
Opportune place; wherefore I shall now but need to take notice, that when
this suppos'd Sulphur (not now to call it rather a kind of _Crocus_) is let
fall by the Liquor upon its Refrigeration, it often settles in Flakes, or
such like parcels of a Yellow Substance, (which being by the precedent
dissolution reduc'd into Minute parts, may peradventure be made to take
Fire much more easily than the Grosser Powder of unprepar'd Antimony would
have done.) Considering therefore, that common Sulphur boyl'd in a
_Lixivium_ may be Precipitated out of it by Rhenish-wine or White-wine,
which are Sowrish Liquors, and have in them, as I elsewhere shew, an Acid
Salt; and having found also by Trial, that with other Acid Liquors I could
Precipitate out of Lixiviate Solvents some other Mineral concretions
abounding with Sulphureous parts, of which sort is crude Antimony, I
concluded it to be easie to Precipitate the Antimony dissolv'd, as was
lately mention'd, with the Acid Oyl of Vitriol; and though common Sulphur
yields a White Precipitate, which the _Chymists_ call _Lac Sulphuris_, yet
I suppos'd the Precipitated Antimony would be of a deep Yellow Colour, as
well, if made with Oyl of Vitriol, as if made only by Refrigeration and
length of Time. From this 'twas easie to deduce this Experiment, that if
you put into one Glass some of the freshly Impregnated and Filtrated
Solution of Antimony, and into another some of the Orange-Colour'd Mixture,
(which I formerly shew'd you how to make with a Mercurial Solution and Oyl
of Tartar) a few drops of Oyl of Vitriol dropp'd into the last mention'd
Glass, would, as I told you before, turn the Deep Yellow mixture into a
Cleer Liquor; whereas a little of the same Oyl dropp'd out of the same Viol
into the other Glass would presently (but not without some ill sent) turn
the moderately cleer Solution into a Deep Yellow Substance, But this, as I
Said, succeeds not well, unless you employ a _Lixivium_ that has but newly
dissolv'd Antimony, and has not yet let it fall. But yet in Summer time, if
your _Lixivium_ have been duly Impregnated and well Filtred after it is
quite cold, it will for some dayes (perhaps much longer than I had occasion
to try) retain Antimony enough to exhibit, upon the Affusion of the
Corrosive Oyl, as much of a good Yellow Substance as is necessary to
satisfie the Beholders of the Possibility of the Experiment.

_Reflections upon the XL. Experiment Compared with the X. and XX._

The Knowledge of the Distinction of Salts which we have propos'd, whereby
they are discriminated into _Acid, Volatile,_ or _Salfuginous_ (if I may
for Distinction sake so call the Fugitive Salts of Animal Substances) and
_fix'd_ or _Alcalizate_, may possibly (by that little part which we have
already deliver'd, of what we could say of its Applicableness) appear of so
much Use in Natural Philosophy (especially in the Practick part of it) that
I doubt not but it will be no Unwelcome Corollary of the Preceding
Experiment, if by the help of it I teach you to distinguish, which of those
Salts is Predominant in Chymical Liquors, as well as whether any of them be
so or not. For though in our Notes upon the X. and XX. Experiments I have
shown you a way by means of the Tincture of _Lignum Nephriticum_, or of
Syrrup of Violets, to discover whether a propounded Salt be Acid or not,
yet you can thereby only find in general that such and such Salts belong
not to the Tribe of Acids, but cannot determine whether they belong to the
Tribe of Urinous Salts (under which for distinction sake I comprehend all
those Volatile Salts of Animal or other Substances that are contrary to
Acids) or to that of Alcalies. For as well the one as the other of these
Salino-Sulphurous Salts will restore the Caeruleous Colour to the Tincture
of _Lignum Nephriticum_, and turn that of Syrrup of Violets into Green.
Wherefore this XL. Experiment does opportunely supply the deficiency of
those. For being sollicitous to find out some ready wayes of discriminating
the Tribes of Chymical Salts, I found that all those I thought fit to make
Tryal of, would, if they were of a Lixiviate Nature, make with Sublimate
dissolv'd in Fair Water an _Orange Tawny_ Precipitate; whereas if they were
of an Urinous Nature the Precipitate would be _White_ and Milky. So that
having alwayes by me some Syrrup of Violets and some Solution of Sublimate,
I can by the help of the first of those Liquors discover in a trice,
whether the propounded Salt or Saline Body be of an Acid Nature or no, if
it be I need (you know) inquire no further; but if it be not, I can very
easily, and as readily distinguish between the other two kinds of Salts, by
the White or Orange-Colour that is immediately produc'd, by letting fall a
few Drops or Grains of the Salt to be examin'd, into a spoonfull of the
cleer Solution of Sublimate. For Example, it has been suppos'd by some
eminently Learned, That when Sal Armoniack being mingled with an Alcaly is
forc'd from it by the Fire in close Vessels, the Volatile Salt that will
thereby be obtain'd (if the Operation be skilfully perform'd,) is but a
more fine and subtile sort of Sal Armoniack, which, 'tis presum'd, this
Operation do's but more exquisitely purifie, than common Solutions,
Filtrations, and Coagulations. But this Opinion may be easily shown to be
Erroneous, as by other Arguments, so particularly by the lately deliver'd
Method of distinguishing the Tribes of Salts. For the Saline Spirit of Sal
Armoniack, as it is in many other manifest Qualities very like the Spirit
of Urine, so like, that it will in a trice make Syrrup of Violets of a
Lovely Green, turn a Solution of good Verdigrease into an Excellent Azure,
and make the Solution of a Sublimate yield a White Precipitate, insomuch
that in most (for I say not all of the Experiments) where I Aim onely at
producing a sudden change of Colour, I scruple not to use Spirit of Sal
Armoniack when it is at hand, instead of Spirit of Urine, as indeed it
seems chiefly to consist (besides the flegm that helps to make it fluid) of
the Volatile Urinous Salt (yet not excluding that of Soot) that abounds in
the Sal Armoniack and is set at liberty from the Sea Salt wherewith it was
formerly associated, and clogg'd, by the Operation of the Alcaly, that
divides the Ingredients of Sal Armoniack, and retains that Sea Salt with it
self. What use may be made of the like way of exploration in that inquiry
which puzzles so many Modern Naturalists, whether the Rich Pigment (which
we have often had occasion to mention) belongs to the Vegetable or Animal
Kingdome, you may find in another place where I give you some account of
what I try'd about Cocheneel. But I think it needless to exemplifie here
our Method by any other Instances, many such being to be met with in divers
parts of this Treatise; but I will rather advertise you, that, by this way
of examining Chymical Liquors, you may not onely in most Cases conclude
_Affirmatively_, but in some Cases _Negatively_. As since Spirit of Wine,
and as far as I have try'd, those Chymical Oyles which Artists call
Essential, did not (when I us'd them as I had us'd the several Families of
Salts upon that Syrrup) turn Syrrup of Violets Red or Green, nor the
Solution of Sublimate White or Yellow, I inferr'd it may thence be probably
argued, that either they are destitute of Salt, or have such as belongs not
to either of the three Grand families already often mention'd. When I went
to examine the Spirit of Oak or of such like Concretes forced over through
a Retort, I found by this means amongst others, that (as I elsewhere show)
these Chymists are much mistaken in it, that account it a simple Liquor,
and one of their Hypostatical Principles: for not to mention what flegm it
may have, I found that with a few drops of one of this sort of Spirits
mix'd with a good proportion of Syrrup of Violets, I could change the
Colour and make it Purplish, by the affinity of which Colour to Redness, I
conjectur'd that this Spirit had some Acid Corpuscles in it, and
accordingly I found that as it would destroy the Blewness of a Tincture of
_Lignum Nephriticum_, so being put upon Corals it would Corrode them, as
common Spirit of Vinegar, and other Acid Liquors are wont to do. And
farther to examine whether there were not a great part of the Liquor that
was not of an Acid nature, having separated the Sour or Vinegar-like part
from the rest, which (if I mistake not) is far the more Copious, we
concluded as we had conjectured, the other or remaining part, though it had
a strong taste as well as smell, to be of a nature differing from that of
either of the three sorts of Salts above mention'd, since it did as little
as Spirit of Wine, and Chymical Oyls, alter the Colour either of Syrrup of
Violets or Solution of Sublimate, whence we also inferr'd that the change
that had been made of that Syrrup into a Purple Colour, was effected by the
Vinegar, that was one of the two Ingredients of the Liquor, which was wont
to pass for a Simple or Uncompounded Spirit. And, upon this account, 'twas
of the Spirit of Oak (and the like Concretes) freed from it's Vinegar that
I elsewhere told you, that I had not then observ'd it, (and I have repeated
the Tryal but very lately) to destroy the Caeruleous Tincture of _Lignum
Nephriticum_. But this onely, _en passant_; for the Chief thing I had to
add was this, That by the same way may be examin'd and discover'd, divers
changes that are produc'd in Bodies either by Nature only, or by Art;
either of them being able by changing the Texture of some Concretes I could
name, to qualifie them to Operate after a New manner upon the above
mention'd Syrrup, or Solution, or both. And by this means, to tell you that
upon the by, I have been able to discover, that there may be made Bodies,
which though they run _per Deliquium_, as readily as Salt of Tartar, belong
in other respects, not to the family of Alcaliz, much less to that of
Salfuginous, or that of Acid Salts. Perhaps too, I may know a way of making
a highly operative Saline Body that shall neither change the Colour of
Syrrup of Violets, nor Precipitate the Solution of Sublimate; And, I can
likewise if I please conceal by what Liquors I perform such changes of
Colour, as I have been mentioning to you, by quite altering the Texture of
some ordinary Chymical productions, the Exploration of which is the main
use of the fortieth Experiment, which I think teaches not a little, if it
teach us to discover the nature of those things (in reference to Salt) that
are obtain'd by the ordinary Chymical Analysis of mix'd Bodyes, though
perhaps there may be other Bodyes prepar'd by Chymistry which may have the
same Effects in the change of Colours; and yet be produc'd not from what
Chymists call the Resolution of Bodies, but from their Composition. But the
discoursing of things of this nature is more proper for another place. I
shall now onely add, what might perhaps have been more seasonably told you
before; That the Reason why the way of Exploration of Salts hitherto
deliver'd, succeeds in the Solution of Sublimate, depends upon the
particular Texture of that Solution, as well as upon the differing Natures
of the Saline Liquors imploy'd to Precipitate it. For Gold dissolv'd in
_Aqua Regia_, whether you Precipitate it with Oyl of Tartar which is an
Alcaly, or with Spirit of Urine, or Sal Armoniack which belongs to the
family of Volatile Salts, will either way afford a Yellow substance: though
with such an Acid Liquor, as, I say not Spirit of Salt, the Body that
yields it, being upon the matter an Ingredient of _Aqua Regis_, but Oyl of
Vitriol it self, I did not find that I could Precipitate the Metall out of
the Solution, or destroy the Colour of it, though the same Oyl of Vitriol
would readily Precipitate Silver dissolv'd in _Aqua-fortis_. And if you
dissolve pure Silver in _Aqua-fortis_, and suffer it to shoot into
Crystals, the cleer Solution of these made in fair Water, will afford a
very White Precipitate, whether it be made with an Alcaly, or an Acid
Spirit, as that of Salt, whereas, which may seem somewhat strange, with
Spirit of Sal Armoniack (that I us'd was made of Quicklime) I could obtain
no such White Precipitate; that Volatile Spirit, nor (as I remember) that
of Urine, scarce doing any more than striking down a very small quantity of
Matter, which was neither White nor Whitish, so that the remaining Liquor
being suffer'd to evaporate till the superfluous Moisture was gone, the
greatest part of the Metalline Corpuscles with the Saline ones that had
imbib'd them, concoagulated into Salt, as is usual in such Solutions,
wherein the Metall has not been Precipitated.

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