FIBRIN FROM SILK. 199 



infusion of nutgalls is added an abundant white precipitate sepa- 

 rates. W hen the solution is diluted with water this matter falls 

 like a jelly to the bottom, but is again dissolved by agitation. 

 When potash is added white flocks fall down, but they are again 

 dissolved, when a great excess of potash is added. 



Fibrin of silk is soluble in muriatic acid at the common tem- 

 perature. When heat is applied the colour becomes brown. It 

 is soluble in nitric acid at the common temperature of the at- 

 mosphere, with the exception of a few flocks, which remain un- 

 dissolved. When heat is applied to the solution oxalic acid is 

 formed. In phosphoric and pyrophosphoric acids it is insoluble 

 at the common temperature of the atmosphere, but dissolves rea- 

 dily when the action of the acid is assisted by heat. 



In weak potash ley it remains unaltered, but when the ley is 

 strong the fibrin dissolves in it by the assistance of heat. On 

 adding water to the solution the fibrin separates in flocks. Sul- 

 phuric acid also throws it^down in minute threads. It is very 

 remarkable that when this fibrin is precipitated from its solutions 

 it always assumes the form of minute threads. When mixed 

 with dry caustic potash and heated while the mixture is kneaded 

 together (unter kneten), it is converted into oxalic acid, as Gay 

 Lussac had already observed to have been the case with silk. 



It is insoluble in carbonate of potash and in liquid ammonia. 



When fibrin of silk is burnt in a platinum crucible a consi- 

 derable quantity of salt remains behind, which cannot be sepa- 

 rated from the fibrin till its texture is destroyed. This ash is 

 partly soluble in water, and the solution reacts weakly as an al- 

 kali. When muriatic acid was poured upon it, an effervescence 

 took place, and the whole was dissolved except a little silica. 

 The solution contained lime, iron, magnesia and soda ; manga- 

 nese, common salt, phosphoric acid, and sulphuric acid. 



Mulder subjected this fibrin to analysis, and obtained,* 

 Carbon, . 47 -99 

 Hydrogen, . 6-57 

 Azote, . 17-35 



Oxygen, . 28-09 



100. 



* Poggeridorf's Amialen, xl. 266. 



