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 fome 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 fo much with fair water, it will not become a yellow liquor. But balsam of fulphur, tho' in a large quantity, it appear to be of a deep red; yet if you fhake 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 mapy 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 fpirit of turpentine, tho' clear as fair water, being digefted upon the pure white fugar of lead, has, in a fhort 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 thefe powders exquifitely, and diftil them in a retort, placed in fand, by degrees of fire; giving, at length, as intense 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, firft unftopped, fend out a great white fume, which fometimes fpreads wide, and is very offenfive: and tho' the liquor itfelf 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 effen tial oil of anifeeds congealed, and fpread 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 fmoke, a blood-red colour. *Mr. Coles found, that a certain fulphu- | the containing glafs, and the liquor will inftantly turn red; tho' they both were clear before. The more the veffel is hook, the deeper will be the red. And this effect is produced without any effervefcence; whence the inventor conceives the experiment may be of use in accounting for fanguification. Philof. Trans. N° 228. p. 542. 36. Let tion of colours. 36. Let it be here obferved, once for all, that, in many of thefe experi- PHYSICS. ments the colour produced is often very fubject to degenerate. However, fince the changes we have fet down happen presently upon the operation of The degenerathe bodies on each other, or at the times fpecified; that is fufficient to fhew 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 duft, 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 leaft in the fuperficial parts, where 'tis exposed 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 expofed to the air, when the window ftood open, of one hue; and the lower part, that was fcreen'd from the air by the wall, of another colour. And Parkinson fays, 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 firft 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 "these rags of cloth, fays he, are thofe ufually call'd turnfol in the druggifts fhops." I alfo 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 fpirit 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 colour. Having diffolved good filver in Aqua fortis, and precipitated it with fpirit of falt, upon first 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 almoft 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 expofed 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. PHYSICS. I have often feen, upon the borders of France, a fort of pear, which, di-. gefted 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 rednefs. Some other obvious changes of colours frequently happen; fuch as is the blacknefs of bodies burned in the open air, c. But I fhall not at prefent examine into the caufes of thefe changes; tho' certainly the reafon why the foots of different bodies are almoft all of them black; why fo much the greater part of vegetables fhould be rather green than of any other colour; and, particularly, why gentle heat, fo frequently, in chymical operations, produces rather a redness, than another colour in digefted menftrua, may very well deferve a ferious inquiry. Different effects of an acid, in led. 37. It may feem ftrange, that if the crimfon folution of cochineal, the the production of juice of black-cherries, or of fome other vegetables that afford the like colours, reconci-colour, be let fall upon a piece of paper; a drop or two of an acid fpirit, fuch as fpirit of falt, or Aqua fortis, will immediately turn it into a fair red; whilst 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. But if we confider the cafe attentively, the action of the acid fpirit feems, 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 produce it in the tincture of cochineal, its operations may be ftill uniform: fince as crimfon 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 fich 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 reftore the folution of cochineal, and the infufion of brazil to the crimfon, from which the spirit of falt had changed them into a truer red; but will alfo heighten the yellow juice of madder into red, and advance the red infufion of brazil to a crimfon. 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 be would give us a faithful account of thofe to be obferved in the fteams of bodies, and of the fubftances they dies, fublimed, or diftilled, and of the productions made by the coalition of form, obferved in thofe fteams. Thus, for inftance, we find in diftilling pure falt-peter,that at a diftillations,&c. certain juncture of the operation, the body, tho' it feem either cryftal line, 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 several other concretes, of different colours and natures; especially when diftill'd with ftrong 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 fpirit 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 diftill'd in Balneo; yet all the waters and fpirits that firft 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 purpofe, by performing that operation in conveniently fhap'd glaffes, wherein the colour of the afcending fumes may be difcern'd; for it might afford a naturalift 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 these 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 glafsmen, by exquifitely mixing a convenient proportion of brimftone, falarmoniac, and quick-filver, and fubliming them together, make a fublimate of an excellent blue. And tho', upon making this experiment, we found the fublimate to be far from a lovely colour, yet, in fome parts, it feem'd bluish, 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 promis'd by fome empirics, who tell us, that orpiment fublim'd, will afford, among the parts of it that fly upwards, fome little maffes, which, tho' the mineral it felf 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, purpofely 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, tho' it confifted not of rubies, yet fmall pieces of its lower part, that were numerous, afforded a pleafant reddifh fparkling colour. 39. Take the dry'd buds, or bloffoms, of the pomegranate-tree, com- Various changes monly called balauftins, pull off the reddifh leaves, and, by a gentle by faline Spirits of colour, caused ebullition, or a competent infufion of them in fair water, extract a in the tinctures faint reddish tincture, which, if the liquor be turbid, you may clarify of vegetables. by the filtre; into this, if you pour a little spirit of urine, or fome other VOL. II. M fpirit, PHYSICS. fpirit, abounding in the like fort of volatile falt, the mixture will prefently turn of a dark greenish colour: but if, inftead of fuch a fpirit, you drop into the fimple infufion, a little rectify'd fpirit of fea-falt, the pale liquor will immediately grow more tranfparent, and acquire a high red, like that of rich claret; and this may as fuddenly be deftroy'd, and turn'd into a dirty bluish green, by the affufion of a moderate quantity of the fpirit of urine. This experiment gives light to two others that I met with in Gaffendus. The experiments as we made them, were thefe. We took a glafs of luke-warm water, and therein immerg'd a quantity of the leaves of fena, upon which there appear'd no redness in the water; but dropping into it a little oil of tartar, the liquor foon became reddifh; tho' by a little oil of vitriol, fuch a colour could not be extracted from the infused fena. On the other hand, we took fome dryed red rofe-leaves, and shaking them in a glafs of fair water, they communicated no redness to it; but upon the affufion of a little oil of vitriol, the water was immediately turn'd red; which it would not have been, if instead of oil of vitriol, we had employ'd oil of tartar. Our author tells us, there was no rednefs either in the water, the leaves of fena, or the oil of tartar ; yet we have found that by fteeping fena for a night in cold water, it would afford a very deep yellow, or reddish tincture, without the help of oil of tartar; which feems to do little more than affift the water more fuddenly to extract a plenty of that red tincture wherewith the leaves of fena abound: for having made a tinEture of fena, only with fair water, and decanted it from the leaves before it grew reddifh, we could not perceive, by dropping fome oil of tartar into it, that the colour was confiderable, tho' it were thereby a little heighten'd into a redness. And the fame thing may be alledg'd in the experiment with red rofe-leaves; for we found that fuch leaves, by bare infufion; for a night and a day, in fair water, afforded a tincture bordering upon rednefs; and that colour being confpicuous in the leaves themfelves, feem'd not wholly produc'd, but extracted by the oil of vitriol. But to improve the experiment, take the tincture of red rofe-leaves, made with a little oil of vitriol, and a large 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 hath acquired a competent redness, without lofing its tranfparency: into this tincture, drop, leifurely a little fpirit of urine; and fhaking the vial, which you must still hold against the light, you will fee the red liquor immediately turn'd into a fine greenish blue; a colour not to be found in any of the bodies upon whofe mixture it enfued. And this change is the more remarkable, because tho' the degeneration of blue into red, be ufual, the turning of red into blue, is very unfrequent. If, upon the falling of each drop of fpirit of urine, you shake the vial containing the red tincture, you may obferve a pretty variety of colours in the paffage of that tincture from a red to a blue. And fometimes we have thus obtain'd fuch a liquor, as being view'd againft, and from the light, feem'd faintly to emulate the tincture of Lignum Nephriticum. And if you make the tincture of red-rofes very high, and, without diluting it with fair water, pour on the |