SERICIN. 



161 



influence may be exercised in the midst of an acid when the oxides 

 in question are capable of forming an insoluble precipitate with 

 the carmin. 



Tannin and astringent principles in general do not precipitate 

 carmin. 



Pelletier and Caventou analyzed carmin in 1818 by means of 

 black oxide of copper, without obtaining any azotic gas. But in 

 a new analysis published by them in 1832, they state the amount 

 of azote in carmin to be 3-56 per cent. But no particulars re- 

 specting the mode of the analysis or the substances obtained are 

 stated. The bare centesimal result is given. So that we have 

 no means of judging the degree of accuracy which was obtained. 

 The following table exhibits their analysis : 

 Carbon, . 49-33 or 32 atoms = 24 or per cent. 49-00 

 Hydrogen, . 6-66 or 24 atoms = 3 ... 6-63 



Azote, . 3-56 or 1 atom = 1-75 ... 3-57 



Oxygen, . 40-45 or 20 atoms = 20-00 ... 40-80 



100-00 48*75 100- 



The carmin subjected to this analysis was previously dried in 

 vacuo by a heat not specified. Pelletier and Caventou think it 

 not unlikely that it still retained a portion of water. 



In the year 1819, M. Lassaigne examined another species of 

 Coccus, the Coccus ilicis, or kermes, which is common in the south 

 of Europe, and which had been employed as a red dye before the 

 introduction of cochineal after the discovery of America. From 

 his experiments it appears that kermes in its nature bears a close 

 resemblance to cochineal, and that it also contains a considerable 

 proportion of carmin, identical in its nature with that from the 

 Coccus cacti.* 



CHAPTER II. 



OF SERICIN, OR THE COLOURING MATTER OF SILK. 



IT is universally known that raw silk is a very fine thread spun 

 by the silk-worm (Bombyx mori,) and in which it envelopes itself 

 while in the chrysalis state. In China there is a silk-worm which 



* Jour, de Pharmacie, viii. 435. 



