"there fuffered to remain for three or four days, with fome beaten alum PHYSICS. put to them, they are afterwards preffed, and the liquor ufually put into bladders, and hung up till it be dry: this, he fays, is afterwards diffol"ved in water, or wine, but canary is the beft to preferve the colour "from starving. The third is a purplish colour, made of the berries, "fuffered to grow upon the bushes, till the middle, or end of November, "when they are ready to fall of themselves." And I try'd, with fuccefs, to make fuch a kind of pigment as painters call fap green, by a way not unlike that here delivered by our author. Much after the fame manner, alfo, they make fap-green in the colour-fhops.. 30. Many bodies, digefted in well-clofed veffels, change their colour in Changes of tract of time, as rectify'd fpirit of hart's-horn; and the fame is evident in colour by dithe precipitations of amalgams of gold and mercury, without addition, gestion, &c. particularly where, by the continuance of a due heat, the filver-coloured amalgam redness.. is reduced into a shining red powder. And many other inftances of the like kind, might be produced. Now, in thefe operations, there appears no reason why we should attribute the new colours to the action of a new substantial form; nor to any increase, or decrease of the falt, fulphur, or mercury of the matter that acquires them. For the veffels are clofed, and these principles, according to the chymifts, are ingenerable, and incorruptible. So that the effect feems to proceed from the heat, agitating and difcompofing the corpufcles of the body expofed to it; which, in procefs of time, fo changes its texture, that the tranfpofed parts modify the incident light, otherwise than when the matter appeared of another colour. 31. Among the feveral changes of colour which bodies acquire, or difclofe, by digeftion, it is very remarkable, that chymifts find a redness, rather than any other colour, in most of the tinctures they draw; and even in the more grofs folutions they make, of almost all concretes that abound either with mineral or vegetable fulphur; tho' the menftruum employ'd about these solutions, or tinctures, be never fo limpid. This we have obferved in abundance of tinctures, drawn with spirit of wine from jalap, guaiacum, and many other vegetables; and not only in the folutions of amber, benjamin, . made with the fame menftruum; but also in feveral mineral tinctures. And, not to urge that familiar inftance of the ruby of fulphur, as chymifts call the folution of flowers of brimftone, made with the spirit of turpentine; nor to take notice of other more known examples of the aptnefs of chymical oils to produce a red colour with the fulphur they extract or diffolve; 'tis remarkable, that both acid and alkaline falts, tho', in most other cafes, of contrary operations, will, with many bodies that abound in fulphureous, or oily parts, produce a red; as is manifeft in the vulgar inftances of the tinctures, or folutions of fulphur, made with lixiviums, either of calcined tartar, or pot-ashes, and other obvious examples; and in that the true glass of antimony, extracted with fome acid spirits, yields a red tincture. And a certain acid liquor will, in a moment, turn oil of turpentine into a deep red.. PHYSICS. red. Among the many inftances I could produce of the eafy production of redness, by the operation of a faline fpirit, as well as of fpirit of wine, two or three of them deferve to be particularly mentioned. 32. But, before I fet them down, 'tis proper to premife, that there feems to be a manifeft difparity betwixt red liquors; for some of them may be faid to have a genuine rednefs, in comparison of others that have it yellowish. Thus if a good tincture of cochineal be diluted never so much with fair water, it will not become a yellow liquor. But balfam of fulphur, tho' in a large quantity, it appear to be of a deep red; yet if you shake the containing glafs, or pour a few drops on a fheet of white paper, fpreading them on it with your finger, what falls back along the fides of the glafs, or ftains the paper, will appear yellow. And there are many tinctures, fuch as that of amber, made with fpirit of wine, which will appear either yellow or red, according as the veffels that contain them are flender or broad. 33. To come now to the experiments we defigned. First, oil or spirit of turpentine, tho' clear as fair water, being digefted upon the pure white fugar of lead, has, in a short time, afforded us a high red tincture; probably a good medicine. 34. Secondly, take common brimftone, and fal-armoniac, of each, finely powdered, five ounces; of beaten quick-lime, fix ounces; mix these powders exquifitely, and diftil them in a retort, placed in fand, by degrees of fire; giving, at length, as intenfe an heat as you can in fand; and there will come over a volatile tincture of fulphur, which alfo may prove an excellent medicine. Now, tho' none of the ingredients here be red, the diftilled liquor is of that colour; and, if it be well drawn, will, upon a little agitation of the vial, first unftopped, send out a great white fume, which fometimes fpreads wide, and is very offenfive: and tho' the liquor itself be red, and its fumes white; yet it will dye the fingers black. 35. The laft experiment, I fhall now produce, to fhew how apt bodies, abounding in fulphureous parts, are to afford a red colour, is one wherein the operation of a clear faline fpirit upon a white, or whitish body, may produce a redness in the twinkling of an eye. We took then, a little ef fential oil of anifeeds congealed, and spread it with a knife upon a piece of white paper; when mixing with it a drop or two of well rectified oil of vitriol, there immediately emerged, with fome heat and smoke, a bloodred colour. Mr. Coles found, that a certain fulphureous fpirit, mixed with a volatile alkali, gives a red colour in a moment. This fpirit he made, by difilling two or three pound of benjamin with a little fand, in a retort, ad ficcitatem; and putting the oil, fpirit, and flowers together in a filtre of paper, when the fpirit came firft thorough. Put two parts of this fpirit to one of spirit of fal-armoniac, and fhake the containing glafs, and the liquor will inftantly turn red; tho' they both were clear before. The more the veffel is fhook, the deeper will be the red. And this effect is produced without any effervescence; whence the inventor conceives the experiment may be of use in accounting for fanguification. Philof. Tranf. N° 228. p. 542. ope- 36. Let it be here obferved, once for all, that, in many of thefe expe- PHYSICS. riments the colour produced is often very fubject to degenerate. However, fince the changes we have fet down happen presently upon the The degeneraration of the bodies on each other, or at the times fpecified; that is fufficient to shew what we intend. For it is not effential to the genuineness of a colour to be durable; a fading leaf, that is ready to rot and moulder into dust, may have as true a yellow as a wedge of gold. And I have feveral times obferved, that the mixture made by the oils of vitriol, and of anifeeds, tho' it acquire a thicker confiftence than either of the ingredients, quickly lofes its colour, and turns to a dark grey; at least in the fuperficial parts, where 'tis expofed to the air. This degeneration of colours may, in many cafes, indeed, proceed from the further action of the faline corpufcles, and other ingredients upon one another; yet much of the fudden change may often be afcribed to the air. Thus we have fometimes obferved window curtains of a light colour, to have that part of them which was exposed to the air, when the window stood open, of one hue; and the lower part, that was fcreen'd from the air by the wall, of another colour. And Parkinson says, of the plant turnfol, that "its berries, when “ full ripe, have within them, between the outward skin and the inward “kernel, a certain juice, which rubbed upon paper or cloth, at the first appears of a fresh lovely green, but prefently changes into a kind of "bluish purple. He adds, that the fame cloth, afterwards wet in water, "and wrung out, will turn the water into a claret-colour. And thefe "rags of cloth, fays he, are thofe ufually call'd turnfol in the druggifts shops." I also remember, that letting fome of the deep red juice of buckthorn berries drop upon a piece of white paper, and leaving it there for many hours, till the paper was grown dry again; I found the juice degenerated to a dirty kind of greyish colour; which, in a great part of the ftain'd paper, feem'd not to have fo much as an eye of red: tho' a little spirit of falt, or diffolved alkali, would turn this unpleasant colour into a red or green. And, to fatisfy myfelf that this degeneration of colour did not proceed from the paper, I dropp'd fome of the fame juice upon a white glazed tile; and, permitting it to dry thereon, I found it then alfo loft its 66 66 colour. Having diffolved good filver in Aqua fortis, and precipitated it with fpirit of falt, upon firft decanting the liquor, the remaining matter was purely white; but, after it had lain a while uncovered, the part of it that lay contiguous to the air, not only loft its whitenefs, but appeared of a very dark, and almost blackish colour; but if the part that was contiguous to the air, were gently taken off, the fubjacent part of the fame mafs would appear very white; till that alfo, having continued a while exposed to the air, would likewife degenerate. Whether the air produce this effect by the means of a fubtile falt, by a penetrating moisture, by folliciting the avolation of certain parts of the bodies to which 'tis contiguous, or by fome other way, I leave to be further confidered. 'Twere eafy here to add many other inftances of redness, refulting from the digeftion of bodies. I PHYSICS. I have often feen, upon the borders of France, a fort of pear, which, digefted with a little wine in a veffel exactly clofed, will foon appear throughout of a deep red colour. Nay, even pure white falt of tartar, and limpid fpirit of wine, will, by long digeftion, acquire a redness. Some other obvious changes of colours frequently happen; fuch as is the blackness of bodies burned in the open air, &c. But I fhall not at prefent examine into the causes of these changes; tho' certainly the reason why the foots of different bodies are almost all of them black; why fo much the greater part of vegetables should be rather green than of any other colour; and, particularly, why gentle heat, fo frequently, in chymical operations, produces rather a rednefs, than another colour in digefted menftrua, may very well deferve a ferious inquiry. Different effects of an acid, in the production of colours, reconciled. ons, &c. 37. It may seem strange, that if the crimson folution of cochineal, the juice of black-cherries, or of fome other vegetables that afford the like colour, be let fall upon a piece of paper; a drop or two of an acid spirit, fuch as fpirit of falt, or Aqua fortis, will immediately turn it into a fair red; whilft an infufion of brazil, in fair water, will have its redness deftroy'd by a little fpirit of falt, or Aqua fortis; and be turn'd either yellow or pale. or pale. But if we confider the cafe attentively, the action of the acid spirit seems, in both these experiments, only to weaken the colour of the liquor wherein it falls; and fo tho' it deftroys redness in the tincture of brazil, but produces it in the tincture of cochineal, its operations may be ftill uniform: fince as crimson is little elfe than a very deep red, with perhaps an eye of blue; fo fome kind of reds feem to be little elfe than heightned yellow; and confequently in fuch bodies the yellow feems to be but a diluted red. And accordingly, alkaline folutions, and urinous fpirits, which feem difpos'd to deepen the colours of moft vegetable liquors, will not only restore the folution of cochineal, and the infufion of brazil to the crimson, from which the spirit of falt had changed them into a truer red; but will also heighten the yellow juice of madder into red, and advance the red infufion of brazil to a crimson. But perhaps it will be much fafer to derive these changes from the vary'd texture, than from the peculiar kinds of bodies. The colours of 38. It might greatly contribute to the hiftory of colours, if chymifts the fumes of bo- would give us a faithful account of thofe to be observed in the steams of bodies, and of the dies, fublimed, or distilled, and of the productions made by the coalition of Substances they thofe fteams. Thus, for inftance, we find in diftilling pure falt-peter, that at form, obferved in diftillati a certain juncture of the operation, the body, tho' it feem either crystalline, or white, affords very red fumes; whilft tho' vitriol be either green or blue, its fpirit comes over in whitifh vapours. The like colour I have found in the fumes of feveral other concretes, of different colours and natures, especially when diftill'd with strong fires. And even foot, as black as it is, has fill'd our receivers with white fumes. No lefs obfervable may the diftill'd liquors be, into which fuch fumes convene: for tho', by skill and care, a reddish liquor is attainable from nitre, yet the common spirit of it, in the preparation whereof abundance of thefe red fumes pafs over into the receiver, has no appearance of red. Neither the fpirit of PHYSICS. vitriol, nor of foot, is white; and the empyreumatical oils of woods, and other concretes, are either of a deep red, or of a colour between red and black. But 'tis very remarkable, that notwithstanding the great variety of colours, to be met with in herbs, flowers, and other bodies ufually distill'd in Balneo ; yet all the waters and spirits that first come over by that way of diftillation, leave the colours of the concretes behind them; tho', indeed, there are one or two vegetables, not commonly taken notice of, whofe diftill'd liquors carry over the tincture of the concrete with them. And as in diftillation, fo in fublimation, it were worth while to take notice of what happens to our purpose, by performing that operation in conveniently fhap'd glaffes, wherein the colour of the afcending fumes may be discern'd; for it might afford a naturalist good information, to obferve the agreements, or differences betwixt the colours of the afcending fumes, and thofe of the flowers they compofe by their convention. It is evident, that thefe flowers do, many of them, greatly differ in point of colour; not only from one another, but often from the concretes that afford them. Thus, tho' camphire and brimftone afford flowers much of their refpective colours, except that thofe of brimftone are a little paler than the lumps that yielded them; yet the flowers of red benjamin are either white, or whitifh. And, to omit other inftances, even that black mineral, antimony, may be made to afford flowers, fome of them red, others grey, and which is more ftrange, fome of them purely white. And glafs-men, by exquifitely mixing a convenient proportion of brimftone, fal-armoniac, and quick-filver, and fubliming them together, make a fublimate of an excellent blue. And though, upon making this experiment, we found the fublimate to be far from a lovely colour, yet, in fome parts, it feem'd bluifh, and was, at least, of a colour very different from either of the ingredients; which is fufficient for our prefent purpose. But a much finer colour is promised by fome empirics, who tell us, that orpiment fublim'd, will afford, among the parts of it that fly upwards, fome little maffes, which, though the mineral itfelf be of a good yellow, will be red enough to emulate rubies, both in colour and tranfparency. This experiment may, for ought I know, fometimes fucceed; for I remember, that having in a fmall bolt-head, purposely fublim'd fome powder'd orpiment, we could in the lower part of the fublimate, difcern, here and there, reddish lines; tho' much of the upper part of it confifted of a matter not only purely yellow, but tranfparent. And we have alfo, by this means, obtain'd a fublimate, which, though it confifted not of rubies, yet fmall pieces of its lower part, that were numerous, afforded a pleasant reddifh fparkling colour. 39. Take the dry'd buds, or bloffoms, of the pomegranate-tree, com- Various chan monly called balauftins, pull off the reddifh leaves, and, by a gentle ges of colour, caused by faline ebullition, or a competent infufion of them in fair water, extract a Spirits in the faint reddish tincture, which, if the liquor be turbid, you may clarify tinctures of by the filtre; into this, if you pour a little fpirit of urine, or fome other vegetables. VOL. II. M fpirit, |