304 EREMACAUSIS OR DECAY 



the arrangement of the elements. Their composition is similar, 

 but they are very unlike in character. 



The contact of ammonia and of alkalies in general may be 

 mentioned among 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 ab- 

 sorbs oxygen with much rapidity, and acquires a brown color. 

 The alcohol is found after a short time to contain acetic acid, 

 formic acid, and the products of the decomposition of aldehyde 

 by alkalies, including the resin of aldehyde, 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 ia 

 in reality the effect of the contact. 



It is decaying wood which causes fresh wood around it to as- 

 sume 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 eremacausis, converts the 

 oxygen gas surrounding it into carbonic acid, without change of 

 volume. Now, De Saussure added a certain quantity of hydro- 

 gen 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 oxygen, but a cor- 

 responding quantity of carbonic acid gas had not been formed. 

 The hydrogen and oxygen had disappeared in exactly the 

 same proportion as that in which they combine to form water ; 

 a true combustion of the hydrogen, therefore, had been induced 

 by mere contact with matter in the state of eremacausis. The 

 action of the decaying substance here produced results exactly 



