Experiments and Considerations Touching Colours (1664) by Robert Boyle

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And to begin with the first sort of Colours, 'tis well enough known to
Chymists, that Tin being Calcin'd by fire alone is wont to afford a White
_Calx_, and Lead Calcin'd by fire alone affords that most Common Red-Powder
we call _Minium:_ Copper also Calcin'd _per se_, by a long or violent fire,
is wont to yield (as far as I have had occasion to take notice of it) a
very Dark or Blackish Powder; That Iron likewise may by the Action of
Reverberated flames be turn'd into a Colour almost like that of Saffron,
may be easily deduc'd from the Preparation of that Powder, which by reason
of its Colour and of the Metall 'tis made of is by Chymists call'd, _Crocus
Martis per se_. And that _Mercury_ made by the stress of Fire, may be
turn'd into a Red Powder, which Chymists call Precipitate _per se_, I
elsewhere more particularly declare.

_Annotation I._

It is not unworthy the Admonishing you, (_Pyrophilus_,) and it agrees very
well with our Conjectures about the dependence of the change of a Body's
Colour upon that of its Texture, that the same Metall may by the successive
operation of the fire receive divers Adventitious Colours, as is evident in
Lead, which before it come to so deep a Colour as that of _Minium_, may
pass through divers others.

_Annotation II_.

Not only the _Calces_, but the Glasses of Metalls, Vitrify'd _per se_, may
be of Colours differing from the Natural or Obvious Colour of the Metall;
as I have observ'd in the Glass of Lead, made by long exposing Crude Lead
to a violent fire, and what I have observ'd about the Glass or Slagg of
Copper, (of which I can show you some of an odd kind of Texture,) may be
elsewhere more conveniently related. I have likewise seen a piece of very
Dark Glass, which an Ingenious Artificer that show'd it me profess'd
himself to have made of Silver alone by an extreme _Violence_ (which seems
to be no more than is needfull) of the fire.

_Annotation III_.

Minerals also by the Action of the Fire may be brought to afford Colours
very differing from their own, as I not long since noted to you about the
variously Colour'd Flowers of Antimony, to which we may add the Whitish
Grey-Colour of its _Calx_, and the Yellow or Reddish Colour of the Glass,
where into that _Calx_ may be flux'd.

And I remember, that I elsewhere told you, that Vitriol Calcin'd with a
very gentle heat, and afterwards with higher and higher degrees of it, may
be made to pass through several Colours before it descends to a Dark
Purplish Colour, whereto a strong fire is wont at length to reduce it. But
to insist on the Colours produc'd by the Operation of fire upon several
Minerals would take up farr more time than I have now to spare.

_EXPERIMENT XLVII._

The Adventitious Colours produc'd upon Metalls, or rather with them, by
Saline Liquors, are many of them so well known to Chymists, that I would
not here mention them, but that besides a not un-needed Testimony, I can
add something of my own, to what I shall repeat about them, and divers
Experiments which are familiar to Chymists, are as yet unknown to the
greatest part of Ingenious Men.

That Gold dissolv'd in _Aqua Regia_ ennobles the _Menstruum_ with its own
Colour, is a thing that you cannot (_Pyrophilus_,) but have often seen. The
Solutions of Mercury in _Aqua-fortis_ are not generally taken notice of, to
give any notable Tincture to the _Menstruum_; but sometimes when the Liquor
first falls upon the Quick Silver, I have observ'd a very remarkable,
though not durable, Greenness, or Blewness to be produc'd, which is a
_Phaenomenon_ not unfit for you to consider, though I have not now the
leisure to discourse upon it. Tin Corroded by _Aqua-fortis_ till the
_Menstruum_ will work no farther on it, becomes exceeding White, but as we
elsewhere note, does very easily of it self acquire the consistence, not of
a Metalline _Calx_, but of a Coagulated matter, which we have observ'd with
pleasure to look so like, either to curdled Milk, or curdled Whites of
Eggs, that a person unacquainted with such Solutions may easily be mistaken
in it. But when I purposely prepar'd a _Menstruum_ that would dissolve it
as _Aqua-fortis_ dissolves Silver, and not barely Corrode it, and quickly
let it fall again, I remember not that I took notice of any particular
Colour in the Solution, as if the more Whitish Metalls did not much Tinge
their _Menstruums_, though the conspicuously Colour'd Metalls as Gold, and
Copper, do. For Lead dissolv'd in Spirit of Vinegar or _Aqua-fortis_ gives
a Solution cleer enough, and if the _Menstruum_ be abstracted appears
either Diaphanous or White. Of the Colour of Iron we have elsewhere said
something: And 'tis worth noting, that though if that Metall be dissolv'd
in oyl of Vitriol diluted with water, it affords a Salt or Magistery so
like in colour, as well as some other Qualities, to other green Vitriol,
that Chymists do not improperly call it _Vitriolum Martis_; yet I have
purposely try'd, that, by changing the _Menstruum_, and pouring upon the
filings of Steel, instead of oyl of Vitriol, _Aqua Fortis_, (whereof as I
remember, I us'd 4 parts to one of the Metall) I obtain'd not a Green, but
a Saffron Colour Solution; or rather a thick Liquor of a deep but yellowish
Red. Common Silver, such as is to be met with in Coines, being dissolv'd in
_Aqua fortis_, yields a Solution tincted like that of Copper, which is not
to be wondred at, because in the coining of Silver, they are wont (as we
elsewhere particularly inform you) to give it an Allay of Copper, and that
which is sold in shops for refined silver, is not (so far as we have tryed)
so perfectly free from that ignobler Metall, but that a Solution of It in
_Aqua fortis_, will give a Venereal Tincture to the _Menstruum_. But we
could not observe upon the solution of some Silver, which was perfectly
refin'd, (such as some that we have, from which 8 or 10 times its weight of
Lead has been blown off) that the _Menstruum_ though held against the Light
in a Crystal Vial did manifestly disclose any Tincture, only it seem'd
sometimes not to be quite destitute of a little, but very faint
Blewishness.

But here I must take notice, that of all the Metalls, there is not any
which doth so easily and constantly disclose its unobvious colour as Copper
doth. For not only in acid _Menstruums_ as _Aqua Fortis_ and Spirit of
Vinegar, it gives a Blewish green solution, but if it be almost any way
corroded, it _appears of one of those_ two colours, as may be observ'd in
Verdigreese made several wayes, in that odd preparation of _Venus_, which
we elsewhere teach you to make with Sublimate, and in the common Vitriols
of _Venus_ deliver'd by Chymists; and so constant is the disposition of
Copper, notwithstanding the disguise Artists put upon it, to disclose the
colour we have been mentioning, that we have by forcing it up with _Sal
Armoniack_ obtain'd a Sublimate of a Blewish Colour. Nay a famous Spagyrist
affirms, that the very Mercury of it is green, but till he teach us an
intelligible way of making such a Mercury, we must content ourselves to
inform you, that we have had a Cupreous Body, that was Praecipitated out of
a distill'd Liquor, that seem'd to be the the Sulphur of _Venus_, and
seem'd even when flaming, of a Greenish Colour. And indeed Copper is a
Metall so easily wrought upon by Liquors of several kinds, that I should
tell you, I know not any Mineral, that will concurr to the production of
such a variety of Colours as Copper dissol'd in several _Menstruums_, as
Spirit of Vinegar, _Aqua fortis_, _Aqua Regis_, Spirit of Nitre, of Urine,
of Soot, Oyls of several kinds, and I know not how many other Liquors, if
the variety of somewhat differing colours (that Copper will be made to
assume, as it is wrought upon by several Liquors) were not comprehended
within the Limits of Greenish Blew, or Blewish Green.

And yet I must advertise you (_Pyrophilus_) that being desirous to try if I
could not make with crude Copper a Green Solution without the Blewishness
that is wont to accompany its Vulgar Solutions, I bethought my self of
using two _Menstruums_, which I had not known imploy'd to work on this
Metall, and which I had certain Reasons to make Tryal of, as I successfully
did. The one of these Liquors (if I much misremember not) was Spirit of
Sugar distill'd in a Retort, which must be warily done, (if you will avoid
breaking your glasses) and the other, Oyl or Spirit of Turpentine, which
affords a fine Green Solution that is useful to me on several occasions.
And yet to shew that the adventitious colour may result, as well from the
true and permanent Copper it self, as the Salts wherewith 'tis corroded, I
shall add, that if you take a piece of good _Dantzick_ Copperis, or any
other Vitriol wherein _Venus_ is praedominant, and having moistened it in
your Mouth, or with fair water, rubb it upon a whetted knife, or any other
bright piece of Steel or Iron, it will (as we have formerly told you)
present'y stain the Steel with a Reddish colour, like that of Copper, the
reason of which, we must not now stay to inquire.

_Annotation I._

I presume you may have taken notice (_Pyrophilus_) that I have borrowed
some of the Instances mention'd in this 47th Experiment, from the
Laboratories of Chymists, and because in some (though very few) other
passages of this Essay, I have likewise made use of Experiments mention'd
also by some Spagyrical Writers, I think it not amiss to represent to you
on this Occasion once for all, some things besides those which I intimated
in the praeamble of this present Experiment; For besides, that 'tis very
allowable for a Writer to repeat an Experiment which he invented not, in
case he improve it; And besides that many Experiments familiar to Chymists
are unknown to the generality of Learned Men, who either never read
Chymical processes, or never understood their meaning, or never durst
believe them; besides these things, I say, I shall represent, That, as to
the few Experiments I have borrowed from the Chymists, if they be very
Vulgar, 'twould perhaps be difficult to ascribe each of them its own
Author, and 'tis more than the generality of Chymists themselves can do:
and if they be not of very known and familiar practise among them, unless
the Authors wherein I found them had given me cause to believe, themselves
had try'd them, I know not why I might not set them down, as a part of the
_Phaenomena_ of Colours which I present you; Many things unanimously enough
deliver'd as matters of fact by (I know not how many Chymical Writers)
being not to be rely'd on, upon the single Authority of such Authors: For
Instance, as some Spagyrists deliver (perhaps amongst several deceitful
processes) that _Saccarum Saturni_ with Spirit of Turpentine will afford a
Balsom, so _Beguinus_ and many more tell us, that the same Concrete
(_Saccarum Saturni_) will yield an incomparably fragrant Spirit, and a
pretty Quantity of two several Oyles, and yet since many have complain'd,
as well as I have done, that they could find no such odoriferous, but
rather an ill-sented Liquor, and scarce any oyl in their Distillation of
that sweet Vitriol, a wary person would as little build any thing on what
they say of the former Experiment, as upon what they averr of the later,
and therefore I scrupled not to mention this Red Balsom of which I have not
seen any, (but what I made) among my other experiments about redness.

_Annot. II._

We have sometimes had the Curiosity to try what Colours Minerals, as
Tinglass, Antimony, Spelter, &c. would yield in several _Menstruums_, nor
have we forborn to try the Colours of stones, of which that famous one,
(which _Helmont_ calls _Paracelsus's Ludus_) though it be digg'd out of the
Earth and seem a true stone, has afforded in _Menstruums_ capable to
dissolve so solid a stone, sometimes a Yellowish, sometimes a Red solution
of both which I can show you. But though I have from Minerals obtain'd with
several _Menstruums_ very differing Colours, and some such as perhaps you
would be surpriz'd to see drawn from such Bodies: yet I must now pass by
the particulars, being desirous to put an End to this Treatise, before I
put an end to your Patience and my own.

_Annotation III._

And yet before I pass to the next Experiment, I must put you in mind, that
the Colours of Metals may in many cases be further alter'd by imploying,
either praecipitating Salts, or other convenient Substances to act upon
their Solutions. Of this you may remember, that I have given you several
Instances already, to which may be added such as these, That if Quicksilver
be dissolv'd in _Aqua fortis_, and Praecipitated out of the Solution, either
with water impregnated with Sea salt, or with the spirit of that Concrete,
it falls to the Bottom in the form of a white powder, whereas if it be
Praecipitated with an Alcaly, it will afford a Yellowish or tawny powder,
and if there be no Praecipitation made, and the _Menstruum_ be drawn off
with a convenient fire, the corroded Mercury will remain in the bottom, in
the form of a substance that may be made to appear of differing Colours by
differing degrees of Heat; As I remember that lately having purposely
abstracted _Aqua fortis_ from some Quicksilver that we had dissolv'd in it,
so that there remain'd a white _Calx_, exposing that to several degrees of
Fire, and afterwards to a naked one, we obtain'd some new Colours, and at
length the greatest part of the _Calx_ lying at the Bottome of the Vial,
and being brought partly to a Deep Yellow, and partly to a Red Colour, the
rest appear'd elevated to the upper part and neck of the Vial, some in the
form of a Reddish, and some of an Ash-Colour Sublimate. But of the
differing Colours which by differing wayes and working of Quick Silver with
Fire, and Saline Bodies, may be produc'd in Precipitates, I may elsewhere
have occasion to take further notice. I also told you not long since, that
if you corrode Quick-silver with Oyl of Vitriol instead of _Aqua-fortis_,
and abstract the _Menstruum_, there will remain a White _Calx_ which by the
Affusion of Fair Water presently turns into a Lemmon Colour. And ev'n the
_Succedaneum_ to a _Menstruum_ may sometimes serve the turn to change the
Colours of a Metal. The lovely Red which Painters call Vermillion, is made
of Mercury, which is of the Colour of Silver, and of Brimstone which is of
Kin to that of Gold, Sublim'd up together in a certain proportion, as is
vulgarly known to Spagyrists.

_EXPERIMENT XLVIII._

The third chief sort of the Adventitious Colours of Metals, is, that which
is produc'd by associating them (especially when Calcin'd) with other
fusible Bodies, and Principally Venice, and other fine Glass devoid of
Colour.

I have formerly given you an Example, whereby it may appear, that a Metal
may impart to Glass a Colour much differing from its own, when I told you,
how with Silver, I had given Glass a lovely Golden Colour. And I shall now
add, that I have Learn'd from one of the Chief Artificers that sells
Painted Glass, that those of his Trade Colour it Yellow with a preparation
of the _Calx_ of Silver. Though having lately had occasion among other
Tryals to mingle a few grains of Shell-silver (such as is imploy'd with the
Pensil and Pen) with a convenient proportion of powder'd Crystal Glass,
having kept them two or three hours in fusion, I was surpriz'd to find the
Colliquated Mass to appear upon breaking the Crucible of a lovely Saphirine
Blew, which made me suspect my Servant might have brought me a wrong
Crucible, but he constantly affirm'd it to be the same wherein the Silver
was put, and considerable Circumstances countenanc'd his Assertion, so that
till I have opportunity to make farther Tryal, I cannot but suspect, either
that Silver which is not (which is not very probable) brought to a perfect
Fusion and Colliquation with Glass, may impart to it other Colours than
when Neal'd upon it, or else (which is less unlikely) that though Silver
Beaters usually chuse the finest Coyn they can get, as that which is most
extensive under the Hammer, yet the Silver-leaves of which this Shel-silver
was made, might retain so much Copper as to enable it to give the
predominant tincture to the Glass.

For, I must proceed to tell you (_Pyrophilus_) as another instance of the
Adventitious Colours of Metals, that which is something strange, Namely,
That though Copper Calcin'd _per se_ affords but a Dark and basely Colour'd
_Calx_, yet the Glassmen do with it, as themselves inform me, Tinge their
Glass green. And I remember, that when once we took some crude Copper, and
by frequent Ignition quenching it in Water had reduc'd it to a Dark and
Ill-colour'd Powder, and afterward kept it in Fusion in about a 100. times
its weight of fine Glass, we had, though not a Green, yet a Blew colour'd
Mass, which would perhaps have been Green, if we had hit right upon the
Proportion of the Materials, and the Degree of Fire, and the Time wherein
it ought to be kept in Fusion, so plentifully does that Metal abound in a
Venerial Tincture, as Artists call it, and in so many wayes does it
disclose that Richness. But though Copper do as we have said give somewhat
near the like Colour to Glass, which it does to _Aqua-fortis_, yet it seems
worth inquiry, whether those new Colours which Mineral Bodies disclose in
melted Glass, proceed from the Coalition of the Corpuscles of the Mineral
with the Particles of the Glass as such, or from the Action (excited or
actuated by fire) of the Alcalizate Salt (which is a main Ingredient of
Glass,) upon the Mineral Body, or from the concurrence of both these
Causes, or else from any other. But to return to that which we were saying,
we may observe that _Putty_ made by calcining together a proportion of Tin
and Lead, as it is it self a White _Calx_, so does it turn the _Pitta di
Crystallo_ (as the Glassmen call the matter of the Purer sort of Glass,
wherewith it is Colliquated into a White Mass, which if it be opacous
enough is employ'd, as we elsewhere declare, for White Amel. But of the
Colours which the other Metals may be made to produce in Colourless Glass,
and other Vitrifiable Bodies, that have native Colours of their own, I must
leave you to inform your self upon Tryal, or at least must forbear to do it
till another time, considering how many Annotations are to follow, upon
what has in this and the two former Experiments been said already.

_Annotation I._

When the Materials of Glass being melted with Calcin'd Tin, have compos'd a
Mass Undiaphanous and White, this White Amel is as it were the Basis of all
those fine Concretes that Goldsmiths and several Artificers imploy in the
curious Art of Enamelling. For this White and Fusible substance will
receive into it self, without spoyling them, the Colours of divers other
Mineral substances, which like it will indure the fire.

_Annotation II._

So that as by the present (XLVIII.) Experiment it appears, that divers
Minerals will impart to fusible Masses, Colours differing from their own;
so by the making and compounding of Amels, it may appear, that divers
Bodies will both retain their Colour in the fire, and impart the _same_ to
some others wherewith they were vitrifi'd, and in such Tryals as that
mention'd in the 17. Experiment, where I told you, that ev'n in Amels a
Blew and Yellow will compound a Green. 'Tis pretty to behold, not only that
some Colours are of so fix'd a Nature, as to be capable of mixture without
receiving any detriment by the fire, that do's so easily destroy or spoyl
those of other Bodies; but Mineral Pigments may be mingled by fire little
less regularly and successfully, than in ordinary Dyeing Fatts, the vulgar
Colours are wont to be mingled by the help of Water.

_Annotation III._

'Tis not only Metalline, but other Mineral Bodies, that may be imploy'd, to
give Tinctures unto Glass (and 'tis worth noting how small a quantity of
some Mineral substances, will Tinge a Comparatively vast proportion of
Glass, and we have sometimes attempted to Colour Glass, ev'n with Pretious
Stones, and had cause to think the Experiment not cast away. And 'tis known
by them that have look'd into the Art of Glass, that the Artificers use to
tinge their Glass Blew, with that Dark Mineral _Zaffora_, (some of my
Tryals on which I elsewhere acquaint you) which some would have to be a
Mineral Earth, others a Stone, and others neither the one, nor the other,
but which is confessedly of a Dark, but not a Blew Colour, though it be not
agreed of what particular Colour it is. 'Tis likewise though a familiar yet
a remarkable practise among those that Deal in the making of Glass, to
imploy (as some of themselves have inform'd me) what they call Manganess,
and some Authors call _Magnesia_ (of which I make particular mention in
another Treatise) to exhibit in Glass not only other Colours than its own,
(which is so like in Darkness or blackishness to the Load stone, that 'tis
given by Mineralists, for one of the Reasons of its Latine Name) but
Colours differing from one another. For though they use it, (which is
somewhat strange) to Clarifye their Glass, and free it from that Blewish
Greenish Colour, which else it would too often be subject to, yet they also
imploy it in certain proportions, to tinge their Glass both with a Red
colour, and with a Purplish or Murry, and putting in a greater Quantity,
they also make with it that deep obscure Glass which is wont to pass for
Black, which agrees very well with, and may serve to confirm what we noted
near the beginning of the 44th Experiment, of the seeming Blackness of
those Bodies that are overcharg'd with the Corpuscles of such Colours, as
Red, or Blew, or Green, &c. And as by several Metals and other Minerals we
can give various Colours to Glass, so on the other side, by the differing
Colours that Mineral Oars, or other Mineral Powders being melted with Glass
disclose in it, a good Conjecture may be oftentimes made of the Metall or
known Mineral, that the Oar propos'd, either holds, or is most of kin to.
And this easie way of examining Oars, may be in some cases of good use, and
is not ill deliver'd by _Glauber_, to whom I shall at present refer you,
for a more particular account of it: unless your Curiosity command also
what I have observ'd about these matters; only I must here advertise you,
that great circumspection is requisite to keep this way from proving
fallacious, upon the account of the variations of Colour that may be
produc'd by the differing proportions that may be us'd betwixt the Oar and
the Glass, by the Richness or Poorness of the Oar it self, by the Degree of
Fire, and (especially) by the Length of Time, during which the matter is
kept in fusion; as you will easily gather from what you will quickly meet
with in the following Annotation upon this present 48th Experiment.

_Annotation IV._

There is another way and differing enough from those already mention'd, by
which Metalls may be brought to exhibit adventitious Colours: For by This,
the Metall do's not so much impart a Colour to another Body, as receive a
Colour from it, or rather both Bodies do by the new Texture resulting from
their mistion produce a new Colour. I will not insist to this purpose upon
the Examples afforded us by yellow Orpiment, and common Sea Salt, from
which, sublim'd together, Chymists unanimously affirm their White or
Crystalline Arsenick to be made: But 'tis not unworthy our noting, That
though Yellow Orpiment be acknowledg'd to be the Copiousest by far of the
two Ingredients of Arsenick, yet this last nam'd Body being duely added to
the highest Colour'd Metall Copper, when 'tis in fusion, gives it a
whiteness both within and without. Thus _Lapis Calaminaris_ changes and
improves the Colour of Copper by turning it into Brass. And I have
sometimes by the help of Zinck duely mix'd after a certain manner, given
Copper one of the Richest Golden Colours that ever I have seen the Best
true Gold Ennobled with. But pray have a care that such Hints fall not into
any hands that may mis-imploy them.

_Annotation V._

Upon the Knowledge of the differing wayes of making Minerals and Metalls
produce their adventitious Colours in Bodies capable of Vitrification,
depends the pretty Art of making what Chymists by a Barbarous Word are
pleas'd to call _Amanses_, that is counterfeit, or factitious Gemms, as
Emeralds, Rubies, Saphires, Topazes, and the like. For in the making of
these, though pure Sand or Calcin'd Crystal give the Body, yet 'tis for the
most part some Metalline or Mineral _Calx_, mingled in a small proportion
that gives the Colour. But though I have many years since taken delight, to
divert my self with this pleasing Art, and have seen very pretty
Productions of it, yet besides that I fear I have now forgot most of the
little Skill I had in it, this is no place to entertain you with what would
rather take up an intire Discourse, than be comprehended in an Annotation;
wherefore the few things which I shall here take notice of to you, are only
what belong to the present Argument, Namely,

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