PHYSICS. fpirit, abounding in the like fort of volatile falt, the mixture will pre fently turn of a dark greenish colour: but if, inftead of fuch a fpirit,. you drop into the fimple infusion, 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 destroy'd, and turn'd into a dirty bluish green, by the affufion of a moderate quantity of the spirit 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 glass 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 reddish; tho' by a little oil of vitriol, fuch a colour could not be extracted from the infufed fena. On the other hand, we took fome dryed red rofe-leaves, and fhaking 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 redness either in the water, the leaves of fena, or the oil of tartar; yet we have found that by steeping 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 tincture of fena, only with fair water, and decanted it from the leaves before it grew reddish, 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 rednefs. 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 redness; and that colour being confpicuous in the leaves themselves, 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 spirit of urine; and shaking the vial, which you muft ftill hold against the light, you will fee the red liquor immediately turn'd into a fine greenifh 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 against, and from the light, feem'd faintly to emulate the 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 fpirit of urine, you may have a blue fo deep as to render the liquor PHYSICS. opake; but if it be dropp'd upon white paper, the colour will foon difclose itself. Having, alfo, made the red, and confequently the blue tin&ture very transparent, and fuffer'd it to reft in a small open vial for a day or two; we found that not only the blue, but the red colour, likewife, was vanifh'd; the clear liquor remaining of a bright amber colour, at the bottom whereof fubfided a large, light feculency, almoft of the fame colour; which feems to be nothing but the ting'd parts of the rofe-leaves, drawn out by the acid fpirits of the oil of vitriol, and precipitated by the volatile falt of the fpirit of urine. This makes it the more probable, that the redness drawn by the oil of vitriol, was as well an extraction of the tinging parts of the rofes, as a production of rednefs. And lastly, the colour of the tincture of rofes, may be chang'd by many other fulphureous falts; as a ftrong folution of pot-afhes, oil of tartar, &c. tho' these are seldom fo free from feculency, as the spirit of urine becomes by diftillation. And I have a way of producing a full purple, by employing a liquor not made red artificially, instead of the tincture of red-rofes; for having by infufing the powder of log-wood for a while in fair water, made that liquor red, I dropp'd into it a little urinous spirit, as that of fal-armoniac, by which the colour was inftantly turn'd into a rich and lovely purple. But care must be taken not to let fall into a spoonful of the tincture, above two or three drops of the fpirit, left the colour become fo deep as to make the liquor opake. And if inftead of fair water, I infus'd the log-wood in water, made a little four by the acid fpirit of falt; I obtain'd neither a purple, nor a red, but only a yellow liquor. 40. The following experiment is very furprizing; and, of all I have yet met with, feems the fittest to enforce our doctrine of colours, and to fhew them not to be inherent qualities, flowing from the fubftantial forms of the bodies whereto they are faid to belong; fince by a bare mechanical change of texture, in the minute parts of bodies, colours may, in a moment, be generated quite de novo, and utterly deftroy'd: for there is this difference betwixt the enfuing experiment, and most of the others we deliver, that in this, the colour of a body is not chang'd into another, but betwixt two bodies, each of them, a-part, colourlefs, there is, in a moment, generated a very deep colour, 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, this otherwife permanent colour, will inftantly be fo utterly deftroy'd, as to leave not the leaft fign of any colour in the whole mixture. The experiment is very easy, and thus perform'd. Take good common fubli- 4 colour inmate, and fully fatiate with it what quantity of water you pleafe, care-ftantly generafully filtre the folution thro' clean clofe paper, that it pay drop down clear ted, and perand colourlefs as fountain water. Then, when you would fhow the expefectly destroy'd. riment, put about a fpoonful of it into a fmall wine-glafs, or other convenient veffel, and letting fall therein three or four drops of good oil of tartar per deliquium, well filtred, that it may likewife be without colour, these two limpid liquors will, in the twinkling of an eye, turn into an opake M 2 mixture PHYSICS. mixture of a deep orange-colour; which, by continually fhaking the glafs in your hand, you must prevent from fettling too foon at the bottom. And when the fpectators have view'd this firft change, prefently drop in four or five drops of oil of vitriol, and continuing to fhake the glafs pretty ftrongly, that it may the fooner diffuse itself, the whole colour will now immediately disappear, and all the liquor in the glafs become clear and colourlefs, as before, without the leaft fediment at the bottom. But for the more neat performance of this experiment, obferve, First, not to take too much of the folution of fublimate, nor drop in too much of the oil of tartar, to avoid the neceffity of putting in fo much oil of vitriol, as to caufe an ebullition. Secondly, 'tis convenient to keep the glafs conftantly in motion, both for the better mixing of the liquors, and hindering, as we faid, the yellow fubftance from fubfiding, which it would otherwife foon do; tho' when 'tis fubfided, it will retain its colour, and be deprived of it by the oil of vitriol. Thirdly, if any yellow matter ftick to the fides of the glafs, 'tis but inclining the veffel, till the clarify'd liquor can wafh along it, and the liquor will presently imbibe it, and deprive it of its colour. The chymical My notion of the different natures of the feveral tribes of falts, having. reafon of this led me to devife this experiment; I can eafily affign the chymical reafon phenomenon. of the phenomenon. Having then obferved, that mercury, diffolved in fome menftrua, would yield a dark yellow precipitate; and fuppofing that common water, and the falts that stick to the mercury, would, in this refpect, be equivalent to thofe acid menftrua which work upon the quickfilver, on account of their faline particles; I fubftituted a folution of fublimate in fair water, inftead of a folution of mercury in Aqua fortis, or fpirit of nitre: then, confidering that what makes the yellow colour, is indeed but a precipitate, obtain'd by means of the oil of tartar, which generally precipitates metalline bodies corroded by acid falts; fo that the colour in our cafe refults from the coalition of the mercurial particles with the faline ones, wherewith they were formerly affociated; and with the alkaline particles of the falt of tartar, that float in the oil. Confidering alfo, that very many effects of lixivious liquors upon the folutions of other bodies may be destroyed by acid menftrua, I concluded, that if I chofe a very strong acid liquor, which by its incifive power might undo the work of the oil of tartar, and difperfe again those particles which the other had, by precipi. tation, affociated into fuch minute corpufcles as were, before, fingly invifible, they would disappear again, and confequently leave the liquor as colourless as before the precipitation was made. This feems to be the chymical reafon of the experiment, and is that which induced me to make it. But to give a perfect mechanical folution of the whole phenomenon, is more than I pretend to. However, the yellowness of the mercurial folution, and oil of tartar, feems produced by the precipitation occafioned by the affufion of the latter; as the deftruction of the colour proceeds from the diffipation of that curdled matter, whofe texture is deftroy'd, and the matter itself diffolved into minute and invifible particles, by the ftrong acid menftruum: which is the reafon why there remains no fediment at the bot- PHYSICS. But, to confirm my conjecture as to the chymical reafon of our experiment, I might add, that I cannot only make the mercury precipitate out of the firft fimple folution quite of a different colour from that mentioned ; but if, inftead of altering the precipitating liquor, I altered the texture of the fublimate in fuch a manner, as my notion about falts requires, I can produce the fame phenomenon. For having fublimed together equal parts of fal-armoniac, and fublimate, firft diligently mixed, the afcending flowers diffolved in fair water, and filtred, gave a folution limpid and colourlefs, like that of the other fublimate; and yet an alkali dropped into this liquor, did not turn it yellow, but white. And, upon the fame foundation, we may with quickfilver, unaffifted by common fublimate, prepare another fort of flowers diffoluble in water, without difcolouring it; which will alfo change its colour in the fame manner. And fo much does the colour depend upon the texture refulting from the convention of the feveral forts of particles, that tho', in our experiment, oil of vitriol destroys the yellow colour; yet with quickfilver, and fair water, by the help of oil of vitriol alone, we may easily make a kind of precipitate, of a fair and permanent yellow; as we fhall fee hereafter. I here make choice of oil of vitriol, because, when well rectified, 'tis not only colourless and scentless, but extremely strong and incifive. And common Aqua fortis will not perform the fame thing fo well. This experiment may be feveral times repeated with the fame parcels of the liquors; for I found, that after I had clarify'd the orange-coloured mixture, by the addition of as little of the oil of vitriol as would fuffice to produce the effect, I could, at pleasure, re-produce the opake colour, by dropping in fresh oil of tartar; and deftroy it again, by the re-affufion of more of the acid menftruum: tho', by the addition of fo much new liquor, in proportion to the mercurial particles, the colour will, at length, appear weak and faint. By boiling crude antimony in a strong and clear lixivium, you may fepa- The preceding rate a fubftance from it, call'd by fome chymifts its fulphur; which, experiment vawhen let fall by the liquor, upon its refrigeration, often fettles in flakes of ried. a yellow fubftance. Confidering therefore, that common fulphur, boiled in a lixivium, may be precipitated out of it by Rhenish, or white-wine, which are fourish liquors, and contain an acid falt; and having found, by tryal, that with other acid liquors I could precipitate out of lixivious folvents, fome other mineral concretions, abounding with fulphureous parts, of which fort is crude antimony; I concluded it eafy to precipitate the antimony, thus diffolved, with the acid oil of vitriol. And tho' common fulphur yields a white precipitate, called Lac Sulphuris; yet I fuppofed the precipitated antimony would be of a deep yellow colour; as well, if made with oil of vitriol, as by refrigeration, and length of time. From hence 'twas easy to deduce this experiment, that if we put into one glafs fome of this די PHYSICS. mixture of a deep orange-colour; which, by continually fhaking the glafs in your hand, you must prevent from fettling too foon at the bottom. And when the fpectators have view'd this firft change, prefently drop in four or five drops of oil of vitriol, and continuing to fhake the glafs pretty ftrongly, that it may the fooner diffuse itself, the whole colour will now immediately disappear, and all the liquor in the glafs become clear and colourlefs, as before, without the leaft fediment at the bottom. But for the more neat performance of this experiment, obferve, First, not to take too much of the folution of fublimate, nor drop in too much of the oil of tartar, to avoid the neceffity of putting in fo much oil of vitriol, as to caufe an ebullition. Secondly, 'tis convenient to keep the glafs conftantly in motion, both for the better mixing of the liquors, and hindering, as we faid, the yellow fubftance from fubfiding, which it would otherwife foon do; tho' when 'tis fubfided, it will retain its colour, and be deprived of it by the oil of vitriol. Thirdly, if any yellow matter ftick to the fides of the glafs, 'tis but inclining the veffel, till the clarify'd liquor can wash along it, and the liquor will prefently imbibe it, and deprive it of its colour. The chymical My notion of the different natures of the feveral tribes of falts, having. reafon of this led me to devife this experiment; I can eafily affign the chymical reafon phenomenon. of the phenomenon. Having then obferved, that mercury, diffolved in some menftrua, would yield a dark yellow precipitate; and fuppofing that common water, and the falts that stick to the mercury, would, in this refpect, be equivalent to thofe acid menftrua which work upon the quickfilver, on account of their faline particles; I fubftituted a folution of sublimate in fair water, inftead of a folution of mercury in Aqua fortis, or spirit of nitre: then, confidering that what makes the yellow colour, is indeed but a precipitate, obtain'd by means of the oil of tartar, which generally precipitates metalline bodies corroded by acid falts; so that the colour in our cafe results from the coalition of the mercurial particles with the faline ones, wherewith they were formerly affociated, and with the alkaline particles of the falt of tartar, that float in the oil. Confidering alfo, that very many effects of lixivious liquors upon the folutions of other bodies may be destroyed by acid menftrua, I concluded, that if I chofe a very strong acid liquor, which by its incifive power might undo the work of the oil of tartar, and difperfe again thofe particles which the other had, by precipi. tation, affociated into fuch minute corpufcles as were, before, fingly invifible, they would disappear again, and confequently leave the liquor as colourless as before the precipitation was made. This feems to be the chymical reafon of the experiment, and is that which induced me to make it. But to give a perfect mechanical folution of the whole phenomenon, is more than I pretend to. However, the yellowness of the mercurial folution, and oil of tartar, feems produced by the precipitation occafioned by the affufion of the latter; as the destruction of the colour proceeds from the diffipation of that curdled matter, whofe texture is deftroy'd, and the matter itself diffolved into minute and invifible particles, by the ftrong acid |