292 CHEMICAL TRANSFORMATIONS. 



CHAPTER 11. 



ON THE CAUSES WHICH EFFECT FERMENTATION; DECAY,* 



AND PUTREFACTION. 



Attention has been recently directed to the fact, 

 that a body in the act of combination of decomposi- 

 tion exercises an influence upon any other body with 

 which it may be in contact. Platinum, for example, 

 does not decompose nitric acid ; it may be boiled 

 with this acid without being oxidized by it, even 

 when in a state of such fine division, that it no long- 

 er reflects light (black spongy platinum). But an 

 alloy of silver and platinum dissolves with great ease 

 in nitric acid; the oxidation which the silver suffers, 

 causes the platinum to submit to the same change ; 

 or, in other words, the latter body, from its contact 

 with the oxidizing silver, acquires the property of 

 decomposing nitric acid. 



Copper does not decompose water, even when 

 boiled in dilute sulphuric acid ; but an alloy of cop- 

 per, zinc, and nickel, dissolves easily in this acid 

 with evolution of hydrogen gas. 



Tin decomposes nitric acid with great facility, but 

 water with difficulty ; and yet, when tin is dissolved 

 in nitric acid, hydrogen is evolved at the same time, 

 from a decomposition of the water contained in the 

 acid, and ammonia is formed in addition to oxide 

 of tin. 



In the examples here given, the only combination 

 or decomposition which can be explained by chemi- 

 cal affinity is the last. In the other cases, electrical 



* An essential distinction is drawn in the following part of the work, 

 between decay and putrefaction {Verwesung und FHvlniss)^ and they are 

 shown to depend on different causes ; but as the word decay is not gen- 

 erally applied to a distinct species of decomposition, and does not indi- 

 cate its true nature, I shall in future, at the suggestion of the author, 

 employ the term eremacausis, the meaning of which has been already 

 explained. — Ed. 



