SILK.

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ture, till the whole glutinous matter was extracted ; five pints of water were employedfor this purpose, the fifth being used in rinsing out the residuum. The liquid wrungout from the silk was evaporated first over the fire, but toward the end over a steambath, till it became a dry extract; which in the damaged pieces was black, like extractof liquorice, but in the sound pieces was brown. In all cases the extract so obtainedabsorbed moisture with great avidity. The extract was weighed in its driest state, andthe weight noted, which showed the addition made, by the dressing to the weight ofthe silk. The piece of silk was occasionally weighed in its cleansed state, when dry,as a check upon the preceding experiment.

3. The dry extract was now subjected to a regular chemical analysis, which wasmodified according to circumstances, as follows: 100 parts of it were carefully igni-ted in a platinum capsule; during which a considerable flame and fetid smoke weredisengaged. The ashes or incombustible residuum were examined by the action of dis-tilled water, filtration, as also by that of acids, and other chemical tests, whereby theconstituents of these ashes were .ascertained. In the course of the incineration or cal-cination of the extract from the several samples, I never observed any sparkling prscintillation; whence I inferred that no nitre had been used in the dressing of thegoods, as some persons suggested.

4. Having, in the course of boiling some of the extract from two of the damagedpieces in a little distilled water, felt a urinous odor, I was induced to institute the fol-lowing minute course of researches, in order to discover whether the urine of man hadbeen introduced into the dressing paste of the silk webs. I digested a certain portionof the said extract in alcohol, 60 per cent, over proof, which is incapable of dissolvingthe rice water, or other starchy matter, which might be properly applied to the silk inthe loom. The alcohol, however, especially when aided by a moderate heat, readilydissolves urea, a substance of a peculiar nature, which is the characteristic constituentof human urine. The alcohol took a yellow tint, and being, after subsidence of thesediment, decanted clear otf into a glass retort, and exposed to the gentle heat of a wa-ter bath, it distilled over clear into the receiver, and left a residuum in the retort, whichpossessed the properties of urea. This substance was solid when cold, but melted at aheat of 220° F .; and at a heat of about 245° it decomposed with the production of wa-ter and carbonate of ammonia—-the well-known products of urea at that temperature.The exhalation of ammonia was very sensible to the smell, and was made peculiarlymanifest by its browning yellow turmeric paper, exposed in a moist state to the fumes,as they issued from the orifice of the glass tube, in which the decomposition was usuallyeffected. I thus obtained perfect evidence that urine had been employed in India inpreparing the paste with which a great many of the-pieces had been dressed. It isknown to every experienced chemist, that one of the most fermentative or putrefac-tive compositions which can be made, results from the mixture of human urine withstarchy or gummy matter, such as rice water; a substance which, by the test of iodinewater, these Corahs also contained, as I showed to the gentlemen present, at my visitto the Bonding Warehouse.

5. On incinerating the extract of the Corahs, I obtained, in the residuum, a notablequantity of free alkali; which, by the test of chloride of platinum, proved to be potassa.But, as the extract itself was neutral to the tests of litmus and turmeric paper, I.wasconsequently led to infer that the said extract contained some vegetable acid, probablyproduced by the fermentation of the weaver’s dressing, in the hot climate of Hindostan.I, accordingly, examined the nature of this acid, by distilling a portion of the extractalong with some very dilute sulphuric acid, and obtained in the receiver a notablequantity of the volatilized acid condensed. This acid might be the acetic (vinegar),the result of fermentation, or it might be the formic or acid of ants, the result of theaction of sulphuric acid upon starchy matter. To decide this point, I saturated the saiddistilled acid with magnesia, and obtained on evaporation the characteristic gummymass of acetate of magnesia, soluble in alcohol, but none of the crystals of formiate ofmagnesia, insoluble in alcohol. From the quantity of alkali (potassa) which I obtainedfrom the incineration of the extract of one piece of the damaged silk, and which^mounted to six grains at least, I was convinced that wood ashes had been added, inIndia , to the mixture of sour rice water and urine, which would therefore constitute acompound remarkably hygrometric, and well qualified to keep the warp of the webdamp,-even in that arid atmosphere, during the time that the Tanty or weaver wasWorking upon it. The acetate of potassa, present in the said Corahs, is one of themost deliquescent salts known to the chemist: and, when mixed with fermented urine,forms a most active hygrometric dressing—one, likewise, which will readily generatemildew upon woven goods, with the aid of heat and the smallest portion ol atmospheric°xygen. By the above-mentioned fermentative action, the carbon, which is one of thechemical constituents of the rice or starchy matter, had been eliminated, so as to occa-