OBSERTER AND RECORD 



OP AGRICULTURE, SCIENCE, AND ART. 



EDITED BY D. PEIRCE. 



No. !«.] 



Philadelpliia, Monday, September 2, ISasl. 



[Vol. I. 



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ON BLEACHING SILK. 



BT M. ROAD. 



White raw silk becomes still whiter 

 by the sun; the fine yellow silk entirely 

 loses its color, and becomes of a good 

 white; the dirty yellow silk acquires, by 

 a long exposure to the light, a dingy red- 

 dish white color. Yellow silk, partly 

 bleached by soap, being exposed for four 

 or five days to the sun, is rendered of 

 many shades of white. 



Yellow raw silk, boiled for eight hours 

 in water, and the water evaporated, left — 

 1, a dry, friable, reddish, resin-like sub- 

 stance, very soluble in water; 2, coloring 

 matter very soluble in alcohol, forming 

 a greenish-yellow solution; 3, a substance 

 insoluble in boiling water, soluble in hot 

 alcohol, and falling down as it cools in 

 light and very white flakes; 4, a black- 

 ish brown residue, burning like animal 

 substances, insoluble in water or alcohol, 

 but soluble in concentrated acids. White 

 raw silk yields the same products, ex- 

 cept the coloring matter. Yellow raw 

 silk was boiled for some hours in alco- 

 hol, and the solution poured off while 

 hqt. The solution was very clear, and of 

 a fine gold color, more or less deep: on 

 cooling, a flaky substance fell down, and 

 remained upon the filter in the form of a 

 fine, yellow, opake jelly, which was 

 much reduced by drying, and formed 

 only very light and thin pellicles. The 

 coloring matter was separated from it by 

 cold alcohol. The fat matter, insoluble 

 12 



in cold alcohol, was analogous to wax, 

 spermaceti, and adipocire. 



Fine yellow silk becomes, by this ope- 

 ration, of a good white, but ordinary silk 

 remains colored. This reddish tinge may 

 be given to yellow raw silk, bleached by 

 the sun, by leaving it for some months on 

 the gras's,macerating it inoxy muriatic acid, 

 or by boiling it for some hours in alcohol. 

 Although oxymuriatic acid does not 

 change the color of yellow raw silk, it 

 produces a remarkable change in the 

 gummy substance. Solutions of caustic 

 soda, or of neutralized soda, boiled for 

 several hours on silk, did not take up so 

 much soluble matter as alcohol. 



The good effects of soap have been long 

 known; but it was thought prudent to 

 analyze that made use of, as also the 

 water. The soap was found to contain 

 52 29 percent, of water, 41.58 of oil, and 

 6.13 of soda: but, according to Lelievre, 

 Darcet, and Pellitier, the soap they exa- 

 mined contained only 30.46 per cent, of 

 water, 60.95 of oil, and S.59 of soda; so 

 that soap may contain more than 20 per 

 cent, of superfluous water, without losing 

 its solid form. 



The Seine water at Paris, yielded, on 

 evaporating, 10 litres (610.3 cub. in.) of 

 it, on an average, 2 grammes (30.8 grains) " 

 of muriate of lime mixed with carbonate, 

 equal to 1.21 grammes of Utne. From 

 this it appears, that in bleaching 30 chilo- 

 grammes, (about 60 lbs.) of silk, with 

 75 (about 15 lbs.) of soap, and 750 (about 

 1500 lbs.) of water, 0.6 (about 1 lb. 5 oz.) 



