Il8 COMMERCIAL FIBRES. 



alkaline filtrate be treated with the acetate of lead the silk will give 

 a white precipitate and the wool a black precipitate. 



Wool contains a certain amount of sulphur silk being entirely 

 free from it. This gives us another means of detection. In a solu- 

 tion of plumbate of soda, wool becomes black while silk is not 

 affected. 



NOTE. For illustrations see lithograph plate at end of Part I. 



