332 EREMACAUSIS OR DECAY 



fermentation or putrefaction proceeds uninterrupted- 

 ly to its completion. It has been remarked, that the 

 mere contact of carbonic acid is sufficient to produce 

 fermentation in the juices of several fruits. 



The contact of ammonia and alkalies in general 

 may be mentioned amongst the chemical conditions, 

 which determine the commencement of eremacausis ; 

 for their presence causes many substances to absorb 

 oxygen and to decay, in which neither oxygen nor 

 alkalies alone produce that change. 



Thus alcohol does not combine with the oxygen 

 of the air at common temperatures. But a solution 

 of potash in alcohol absorbs oxygen with much 

 rapidity, and acquires a brown color. The alcohol is 

 found after a short time to contain acetic acid, form- 

 ic acid, and the products of the decomposition of 

 aldehyde by alkalies, including aldehyde resin, which 

 gives the liquid a brown color. 



The most general condition for the production of 

 eremacausis in organic matter is contact with a body 

 already in the state of eremacausis or putrefaction. 

 We have here an instance of true contagion ; for 

 the communication of the state of combustion is in 

 reality the effect of the contact. 



It is decaying wood which causes fresh wood around 

 it to assume the same condition, and it is the very 

 finely divided woody fibre in the act of decay which 

 in moistened gall-nuts converts the tannic acid with 

 such rapidity into gallic acid. 



A most remarkable and decided example of this 

 induction of combustion has been observed by De 

 Saussure. It has already been mentioned, that moist 

 woody fibre, cotton, silk, or vegetable mould, in the 

 act of fermentation or putrefaction, converts oxygen 

 gas which may surround it into carbonic acid, with- 

 out change of volume. Now, De Saussure added 

 a certain quantity of hydrogen gas to the oxygen, 

 and observed a diminution in volume immediately 

 after the addition. A part of the hydrogen gas had 

 disappeared, and along with it a portion of the oxy- 



