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 BLEACHING. 565 with which it is joined, than this fubftance has, muft fet it at Hence, than what the others have. Alkaline falts diffolve liberty, and make it vifible. Acids attradf alkaline fait from oils, therefore thefe falts diflblve the cellular oil of the cloth, is all the foundation which this theory has to reft all other bodies; and therefore will ferve our purpofe. on ; too flight, when unfupported by experiment,- to be “ Into a quantity of the impregnated lye mentioned in the former experiment, I poured in oil of vitriol. Some relied on. Dr Home endeavours to fettle this queftion by the fol- bubbles of air arofe, an inteftine motion was to be perceived, and the liquor changed its colour from a dark lowing experiments and obfervations. “ Wax, fays he, is whitened by being expofed to the to a turbid white. It curdled like a folution of foap, influence of the fun, air, and moifture. A difcovery of and a fcum foon gathered on the furface, about half an the changes made on it by bleaching, may throw a light inch in thicknefs, the deepnefs of the liquor not being above fix inches. What was below was now pretty clear. upon the queftion. “ Six drachms of wax were diced down, expofed on a A great deal of the fame matter lay in the bottom; and fouth window. Sept. 10. and watered. That day being I obferved, that the fubftance on the furface was preciclear and warm, bleached the wax more than all the fol- pitated, and ftiowed itfelf heavier than water, when the lowing. It feemed to me to whiten quicker when it had particles of air, attached to it in great plenty, were difno water thrown on it, than when it had. Sept. iy. it pelled by heat. This fubftance was in colour darker than was very white, and t drachm 3 grains lighter, g-f. the cloth which had been boiled in it. drachms of this bleached wax, and as much of unbleach- “ I procured a confiderable quantity of it by fldmed, taken from the fame piece, were made into two ming it off. When I tried to mix it with water, it alcandles of the fame length and thicknefs, having cotton ways fell to the bottom. When dried by the air, it diwicks of the fame kind. The bleached candle burned miniftied very much in its fize, and turned as black as a one hour thirty-three minutes; the unbleached three mi- coal. In this ftate it deflagrated ftrongly with nitre in nutes longer. The former run down four times, theJat- fufion; gave a ftrong tinfture to fpirit of wine; and when ter never. The former had an obfcure light and dull put on a red-hot iron, burnt very flowly, as if it conflame ; the latter had a clear pleafant one, of a blue co- tained a heavy ponderous oil; and left fome earth behind. lour at the bottom. The former when burping feemed “ From the inflammability of this fubftance, its reto have its wick thicker,, and its flame nearer the wax, jedling of water, and diflblving in fpirit of wine, we difthan the latter. The former was brittle, the latter not. cover its oleaginous nature; but from its great fpecific It plainly appears from thefe fads, that the unbleached gravity we fee that it differs very much from the exwax was more inflammable than the bleached ; and that prefled or cellular oil of vegetables ; and yet more from the latter Jrad loft fo much of an inflammable fubftance, their mucilage. That it diflblves in fpirit of wine, is not as it had loft in weight; and confequently the fubftance a certain argument of its differing from expreffed oils ; loft in bleaching of wax is the oily part. becaufe thefe, when joined to alkaline falts, and reco“ As I had not an opportunity of repeating the former vered again by acids, become foluble in fpirit of wine. experiment, I do not look on it as entirely conclufive ; The quantity of earthy powder left behind after burning, for it is poflible that fome of the dull, flying about in the fhows that it contains many of the folid particles of the air, might have mixed with the bleached wax, and fo flax. The fubftance extracted from cloth by alkaline have rendered it lefs inflammable. Nor do I think the lyes appears then to be a compofition of a heavy oil, and analogical reafdjing from wax to linen without objec- the folid earthy particles of the flax. tions. Let us try then if we cannot procure the fubftance “ In what manner thefe falts a<ft fo as to diffolve the extraded from the cloth, ftiow it to the eye, and exa- oils, and detach the folid particles, is uncertain; but we mine its different properties. The proper place to find fee evidently how much cloth muft be weakened by an it, is in a lye already ufed, and fully impregnated with. improper ufe of them, as we find the folid particles themthefe colouring particles. felves are feparated.” “ I got in the bleachfield fome lye, which had been It is neceffary that cloth fhould be dry before bucking, ufed all that day for boiling coarfe linen, which was to- that the falts may enter into the body of the cloth along lerably white, and had been twice boiled before. There with the water ; for they will not enter in fuch quantity, could be no drefling remaining in thefe webs. No foap if it be wet; and by ading too powerfully on the exhad ever touched that parcel; nor do they mix foap with ternal threads, may endanger them. the lye ufed for coarfe cloth. Some of this impregnated degree of heat is a very material circumftance in lye was evaporated, and left a dark-coloured matter be- thisThe operation. As the aftion of the falts is always in hind. This fubftance felt oily' betwixt the fingers, but proportion to the heat, it would appear more proper to would not lather in water as foap does. It deflagrated begin with a boiling heat, by which a great deal of time with nitre in fufion, and afforded a tinfture to fpirit of and labour might be faved. The reafon why this method wine. By this experiment the falts feem to have an oily is not followed, appears to be this. If any vegetable or inflammable fubftance joined with them. fubftance is to be foftened, and to have its juices “ Could we feparate this colouring fubftance from vegetable extracted, it is found more proper to give it gentle dethefe falts, and exhibit it by itfelf fo that it might be- grees of heat at firft, and to advance gradually, than to come the obje<ft of experiment, the quelfion would be it all at once in boiling water. This 1 aft degree foon decided. Here chymiftry lends us its afliftance. ofplunge heat is fo ftrong, that when applied at once to a veWhatever has a ftronger affinity or attra&ion to the falts getable, it bardeps, inftead of foftening its texture. Dried Vol. I. No. 24. 3 7D vegetables