It has excited the admiration of fome perfons to fee what a variety of PHYSICS. colours we have fometimes produced in fuch glaffes, by the bare infufion of brazil, variously diluted with fair water, and altered by the infufion of feveral chymical fpirits, and other faline colourless liquors; and when the whole mixture is reduced to an uniform degree of colour, I have made it appear to be of colours gradually differing, by pouring it into glaffes of a conical figure. Or even take a large round vial, fill it with the red infufion of brazil, hold it against the light, and you will difcern a notable difference betwixt the colour of that part of the liquor which is in the body of the vial, and that which is more pervious to the light, in the neck.

I once had a glafs, and a blue liquor, which was chiefly a certain folution of verdigreafe, fo fitted, that tho' in other glaffes the experiment would not fucceed; yet when this particular glafs was filled with that folution, it appeared in the body of the vial of a lovely blue, and in the neck of a manifeft green. I had alfo, a broad piece of glafs, which being viewed against the light, feem'd clear enough; and, held from the light, appeared very little difcoloured: yet it was a piece knock'd off from a great lump of glafs, to which if we rejoin'd it, where it had been broken off, the whole mafs appeared green as grafs.

I have, likewise, feveral times ufed bottles and ftopples, both made of the very fame metal; and yet whilft the bottle appeared only inclining to green, the ftopple was of fo deep a colour, that it could hardly be thought poffible they fhould be the fame materials. And I have by me a fat glafs, on which, if I look against the light with the broad fide obverted to my eye, it appears like a good ordinary window-glafs; but if I turn the edge of it to my eye, and ftand in a convenient polition, with re¬ gard to the light, it emulates an emerald.

I have fometimes made a fluid kind of pigment, which, dropped on a piece of white paper, appears, where any quantity of it falls, of a crimfon colour; but, being fpread thinly on the paper, prefently exhibits a fair green.

pure

Let me add, that having made many experiments with that blue fubftance, called by the painters litmafe; we have fometimes obferved, that › being diffolved in a due proportion of fair water, the folution, either oppofed to the light, or dropped upon white paper, appeared of a deep colour, betwixt crimfon and purple; yet, when fpread very thin on the paper, and fuffered to dry there, the paper was thereby ftain'd of a fine blue. This experiment alfo fucceeded, when made on a flat piece of white glazed earth. And having let fall a few drops of the ftrong infufion of this litmafe, in fair water, into a fine cryftal glafs, fhaped like an inverted cone, and almost fill'd with clear water; I had the pleasure to fee these few tinged drops, variously difperfing themselves thro' the limpid water, exhibit many colours, or varieties of purple and crimfon. But when the corpufcles of the pigment feem'd to have equally diffufed themselves thro' the whole; by adding to it two or three drops of fpirit of falt, we perceived it first made an odd change in the colour of the liquor,

as

PHYSICS. as well as a vifible commotion among its fmall parts, and in a fhort time changed it wholly into a very glorious yellow, like that of a topaz. After this, if I let fall a few drops of a strong heavy folution of pot-afhes, whofe weight would quickly fink it to the fharp bottom of the glafs; there would foon appear four very pleafant and diftinct colours: viz. a faint bright one, at the fharpeft part of the glafs; a purple, a little higher; a deep and glorious crimfon, in the confines betwixt the purple and the yellow; and an excellent yellow, the fame that before adorned the whole liquor, reaching from thence to the top of the glass. And if I poured, very gently, a little fpirit of fal-armoniac upon the upper part of this yellow, there would alfo arife there a purple, or a crimfon, or both; fo that the unaltered part of the yellow liquor appeared intercepted betwixt the two neighbouring colours. Hence we need not be furprized at the tricks of thofe mountebanks, who are commonly called water-drinkers. For tho' not only the vulgar, but many perfons far above that rank, have wondered to fee a man, after drinking large quantities of fair water, return it in the form of claret, fack, and milk; yet having by chance had occafion to oblige a wanderer, who made a profeffion of this, and other juggling tricks, he ingenuously confeffed to me, that the art confifted rather in a few tricks than any great skill in altering the nature and colours of things. And I fufpect there may be a great deal of truth in a little pamphlet, printed long ago in English; wherein the author undertakes to difcover, from the confeffion of fome of the accomplices themselves, that a famous water-drinker, then much admired in England, performed his pretended tranfmutations of liquors by the help of two or three inconfiderable preparations and mixtures of obvious fluids; and chiefly of an infufion of brazil variously diluted and made pale, yellowish, &c. with vinegar. And, for my part, what most surprizes me in this affair, is, that the drinkers can take down fo much water, and fpout it out again with violence; tho' cuftom, and a vomit feafonably taken before-hand, may in fome of them greatly facilitate the work. But as for the changes they make in liquors, thofe are but few and flight.

Changes of co

ture of the menStruum.

46. Helmont ufed to make a preparation of fteel, which a very ingenious ly depend upon chymift fometimes employs for a Succedaneum to the fpaw-waters; dithe peculiar tex-luting this Effentia Martis liquida, as he calls it, with a due proportion of water. And tho' this preparation be almoft of the colour of a German amethyft, and confequently remote from green; yet a very few drops of it being let fall into a large proportion of Rhenish, or white-wine, it immediately turns them to a lovely green. By which phenomenon we may learn how requifite it is in experiments, about the changes of colours, carefully to regard the circumftances of them; for water will not, as I have purpofely try'd, concur to the production of any fuch green; nor did it give that colour to moderate fpirit of wine, wherein I diffolved it: and wine itfelf is a liquor that few would fufpect able, of a fudden, to work any fuch change in a metalline preparation of this nature. And to fatisfy myself that this new colour proceeds rather from the peculiar texture of

the

the wine, than from any greater acidity that Rhenif, or white-wine PHYSICS. has, in comparifon of water; I fharpened the folution of this effence in fair water, with a large quantity of fpirit of falt; and then the mixture acquired no greennefs.

To vary the experiment a little, I try'd, that if into fome Rhenish wine made green by this effence, I dropped an alkaline folution, or urinous fpirit; the wine would prefently grow turbid, and of an odd dirty colour. But if, inftead of diffolving the effence in wine, I diffolved it in fair water, fharpen'd with a little fpirit of falt; then either the urinous fpirit of falarmoniac, or the folution of the fixed falt of pot-afhes, would immediately turn it of a yellowish colour; the fixed or urinous falt precipitating the vitriolic fubftance contained in the effence. And as our effence imparts a greennefs to wine, but not to water; Olaus Wormius tells us of a rare kind of turn-fol he had, whofe beautiful redness would be easily communicated to water, but fcarce to wine, and not at all to fpirit of wine: in which last circumstance it agrees with our effence, tho' they difagree in other particulars.

colours of metals

47. I have often taken notice, that metals, as they appear to the The different eye, before they come to be altered by other bodies, exhibit colours very in different different from thofe which the fire, or a menftruum, either feparately or states. conjointly, produce in them; efpecially confidering, that thefe metalline bodies are, after all their difguizes, reducible not only to their former confiftence, and other more effential properties, but to their colour too; as if nature had given them an external and an internal colour. But, upon a more attentive confideration of this difference of colours, it feems probable to me, that many of thofe we call internal, are rather produced by the coalition of metalline particles with thofe of the falts, or other bodies employ'd to work on them, than by the bare alteration of the parts. of the metals themselves. Of these adventitious colours of metalline bodies, the chief forts feem to be three; viz. fuch as are produced by the fole action of the fire; fuch as emerge from the coalition of metalline particles, with thofe of fome menftruum employ'd to corrode, or precipitate the metal; and, laftly, the colours afforded by metalline bodies, either melted with, or otherwife penetrating into others, efpecially fuch as are fufible.

As to the firft of thefe colours; 'tis well known to chymifts, that tin calcined by fire alone, affords a white calx; and lead, by the fame means, yields that common red powder we call Minium; copper alfo, calcined per fe, by a long or violent fire, gives a very dark or blackish powder; iron, likewife, may, by the action of reverberated flames, be turn'd into a colour almoft like that of faffron, as we fee in the preparation of Crocus Martis per fe; and mercury, by the power of fire, will be turn'd into a red powder, call'd precipitate per fe.

Befides, the fame metal may, by the fucceffive operations of the fire, receive several adventitious colours; as is evident in lead, which, before it arrives at fo deep a colour as that of Minium, may pass thro' feveral Not

others.

PHYSICS.

And, not only the Calces, but the glaffes of metals, vitrify'd per fe, may have colours different from the obvious or natural colours of the metal; as I have obferved in the glafs of lead, made by long expofing that metal crude to a violent fire. I have likewife feen a piece of very dark glafs, which an ingenious artificer, who fhewed it me, profeffed he made of filver alone, by an extreme violence of the fire.

Minerals alfo, by the action of the fire, may be brought to afford colours very different from their own; as was obferved about the variously coloured flowers of antimony. To which we may add, the whitish grey colour of its calx, and the yellow or reddifh one of the glass, into which that calx may be fluxed. And vitriol, calcined with a very gentle heat, and afterwards with higher degrees of it, may be made to pass thro' feveral colours, before it defcends to a dark purplish one, whereto a ftrong fire will at length reduce it.

48. The adventitious colours produc'd in metals, by faline liquors, are many of them, well known to chymifts. That gold, diffolv'd in Aqua regia, communicates its own colour to the menftruum, is a common obfervation; but the folutions of mercury, in Aqua fortis, are not generally obferv'd to give any notable tincture to the menftruum; tho' fometimes, when the liquor firft falls upon the quick-filver, I have obferv'd a very remarkable greennefs, or blueness to be produc'd. Tin, corroded by Aqua fortis, till the menftruum will work no farther on it, becomes exceeding white; and eafily, of it felf, acquires the confiftence not of a metalline calx, but of a coagulated matter, fo like either to curdled milk, or curdled whites of eggs, that a perfon unacquainted with fuch folutions, might easily be mistaken in it. But when I purpofely prepar'd a menftruum that wou'd diffolve it, as Aqua fortis diffolves filver, not barely corrode it, and quickly let it fall again; I remember no particular colour in the folution: as if the more whitish metals did not much tinge their menftrua, tho' the high-colour'd ones, as gold and copper, do. For lead diffolv'd in fpirit of vinegar, or Aqua fortis, gives a clear folution: and, if the menftruum be abstracted, appears either diaphanous, or white. And 'tis worth noting, that tho' when iron is diffolv'd in oil of vitriol, diluted with water, it affords a falt, or magiftery, fo like in colour, as well as fome other qualities, to green vitriol, that chymifts properly call it, Vitriolum Martis; yet, by changing the menftruum, and pouring upon the filings of fteel, Aqua fortis, inftead of oil of vitriol, I obtain'd not a green, but a faffron-colour'd folution, or rather a thick liquor, of a deep yellowish red. Common filver, diffolv'd in Aqua fortis, yields a folution ting'd like that of copper; which is not to be wonder'd at, becaufe, in coining filver, they give it an allay of copper; and what is fold for refin'd filver,is not fo perfectly free from that ignobler metal, but that a folution of it in Aqua fortis will give its tincture to the menftruum. But we could not obferve, upon the folution of fome filver perfectly refin'd, that the menftruum, tho' held against the light, in a crystal vial, manifeftly difclos'd any tincture; only it fometimes feem'd not quite deftitute of a very faint bluifh caft.

But

But, of all the metals, there is not one which fo eafily and conftantly PHYSICS. difclofes its colour as copper. For, in acid menftrua, as Aqua fortis, and fpirit of vinegar, it not only gives a bluish green folution; but if it be almoft any way corroded, it appears of one of thofe two colours. And fo conftant is the difpofition of copper, notwithstanding the difguize artifts put upon it, to discover its colour, that we have, by forcing it up with falarmoniac, obtain'd a fublimate of a bluifh caft. Nay, a famous chymift affirms, that the very mercury of it is green; but till he teaches us an intelligible way of making fuch a mercury, we muft content ourselves to fay, that we have had a cupreous body precipitated out of a diftill'd liquor, which feem'd to be the fulphur of that metal, and even when flaming, appear'd of a greenish colour. And, indeed, copper is a metal To eafily wrought upon, by liquors of feveral kinds, that, I might fay, I know not any mineral which concurs to the production of fuch a variety of colours, as copper diffolv'd in feveral menftrua, viz. fpirit of vinegar, Aqua fortis, Aqua regia, fpirit of nitre, of urine, of foot, oils of feveral kinds, c. if the variety of them were not comprehended within the limits of greenifh blue, or bluish green.

But being defirous to try if I could not with crude copper make a green folution, without the bluishness that ufually accompanies it, I concluded upon two menftrua, which, tho' I had not known employ'd to work on this metal, prov'd fuccessful; the one was fpirit of fugar, and the other, oil, or fpirit of turpentine, which affords a fine green folution, ufeful on feveral occafions. And yet to fhew that the adventitious colour may refult as well from the true and permanent copper it felf, as the falts wherewith 'tis corroded; if you take a piece of good Dantzick copperas, or any other vitriol wherein copper is predominant, and having moiften'd it with fair water, rub it upon a bright piece of iron, or steel it will (as we have formerly faid) prefently ftain it with a reddish colour like that of copper.

We have fometimes try'd what colours fuch minerals as tin-glass, antimony, fpelter, &c. would yield in feveral menftrua. The like we have alfo done with ftones; among which, that famous one call'd by Helmont, Paracelfus's Ludus, has afforded in menftrua able to diffolve fo folid a ftone, fometimes a yellowish, and fometimes a red folution. And from minerals I have obtain'd, with feveral menftrua, very different colours; and fome fuch, as, perhaps, would scarce be expected from fuch bodies.

The colours of metals may, in many cafes, be further alter'd, by employing either precipitating falts, or other convenient fubftances, to act upon their folutions. If quick-filver be diffolv'd in Aqua fortis, and precipitated out of the folution, either by water impregnated with fea-falt, or the fpirit of that concrete, it falls to the bottom in the form of a white powder; but if precipitated with an alkali, it affords a yellowish powder: and if no precipitation be made, and the menftruum be drawn off with a convenient fire, the corroded mercury will remain at the bottom, and may be made to appear of different colours, by different degrees of heat.

VOL. I.

O

Thus