308 Silk Manufacture. 



alembic. Mons. Baume says that silk may be thus madetomaJ 

 or even to surpass in whiteness and lustre the finest specimens 

 from Nankin. 



' The revenue regulations, and the dearness of spirit, make the 

 above process impracticable in England, where the usual method 

 of bleaching raw silk is to immerse it in a boiling solution of good 

 soap in river water. After boiling for two or three hours the silk 

 is taken out, beaten, and then rinsed in cold water ; when this 

 has been sufficiently performed, it is slightly wrung, then put into 

 cold soap and water, tinged with a minute portion of indigo, and 

 again boiled. On removing the silk from this second water, it is 

 wrung as dry as possible with the assistance of wooden pegs, and 

 is then well shaken to separate the threads : after this it is 

 suspended in a kind of stove constructed for the purpose, which 

 contains sulphur in a state of combustion ; the fumes arising from 

 this give the last degree of whiteness to the silk, and the process 

 is completed. 



' Silk is powerfully acted upon by nitric acid. If two drachms 

 of this acid are mixed with a pint of alcohol, and silk, either raw 

 or bleached, be immersed in it, and kept in digestion exposed to a 

 moderate heat for twenty-four hours, the silk becomes of a dull 

 yellowish brown, which, after it has been washed with soap, 

 rinsed, and dried, turns to a fine golden yellow color, which is 

 very permanent. Concentrated nitric acid being distilled of 

 silk, and the remaining liquor partially evaporated, oxalic acid is 

 obtained : if the evaporation be pursued still farther, the residue 

 will yield, together with a small portion more of oxalic acid, a 

 quantity of yellow crystals, not in the slightest degree acid, but 

 intensely bitter, and which stain the skin of a deep yellow color, 

 not easily removed. This curious substance was discovered by 

 Welter, and was called by him the " bitter principle." He sup- 

 posed that its production always results from the action of nitric 

 acid on animal matter. These crystals, when examined through 

 a magnifying glass, appear to be composed of truncated octahe- 

 drons. 



' If the remaining liquor be previously saturated with potass 

 and evaporated, another yellow silky salt separates, which deto- 

 nates on burning coals like nitre, and appears to be a triple 

 combination of the before mentioned bitter substance with nitrate 

 of potass. 



' The water wherein the cocoons are placed to prepare them 

 for reeling, quickly acquires from them so much of the resinous 

 matter as to be more viscid than the strongest soap lather. 

 Chappe found that he could inflate this water into bubbles or 



