40 MODERN SCIENCE READER 



size of silk required, as is the case with natural silk. The 

 silk would soon dry by the evaporation of the alcohol and 

 ether if left exposed to the air; it is therefore kept moist 

 by damp cloths to facilitate the next process of throwing 

 and twisting. This is accompanied by putting on the silk 

 the required number of turns or twists per inch. The 

 reeling or skeining of the silk into a given number of yards 

 in each skein is the next operation. One thousand or two 

 thousand yards is the usual quantity, and according to 

 the weight of skein so is the size designated. The Char- 

 donnet silk is about 30 per cent, heavier in S.G. than na- 

 tural silk, so the comparison of sizes is easily arrived at. 

 The silk is still damp, and should now have the remaining 

 alcohol and ether dried out of it. The inventor claims this 

 to be one of the most important points to give the silk good 

 dyeing properties. 



The silk at this point of manufacture is very inflam- 

 mable and quite unfit for use in textile goods, therefore 

 a process called denitration is next carried out which re- 

 converts our product into cellulose, now very different in 

 appearance from the raw cotton we commenced with, but 

 practically the same in chemical composition. 



One of the substances used for this purpose is sulphy- 

 drate of calcium, and the chemical reaction may be ex- 

 pressed by the following formulae: 



C,H 8 (N0 8 )o 3 + 2 Ca H 2 S 2 = 

 C 6 H 10 5 + 2 Ca N0 2 + H 2 S + S 2 . 



The silk, now it is finished, requires no precautions in 

 manufacturing more than cotton, in fact less, as there 

 should be no loose fiber which can detach itself from the 

 thread. 



The bleaching is carried out in the usual way for vege- 

 table fibers with chloride of lime and acid. 



Up to the present time artificial silk has always been 

 used in conjunction with other fibers in textile goods; the 

 friction of weaving has a tendency to split the threads if 



