296 EREMACAUSIS, OR DECAY; 



The conditions which determine the commencement of erema. 

 causis are of various kinds. Many organic substances, par- 

 ticularly such as are mixtures of several more simple matters, 

 oxidize in the air when simply moistened with water ; others not 

 until they are subjected to the action of alkalies ; but the greatest 

 part of them undergo this state of slow combustion or oxidation, 

 when brought in contact with other matters already in a state 

 of decay. 



The eremacausis of an organic matter is retarded or completely 

 arrested by all those substances which prevent fermentation or 

 putrefaction. Mineral acids, salts of mercury, aromatic sub- 

 stances, empyreumatic oils, and oil of turpentine, possess a simi- 

 lar action in this respect. The latter substances have the same 

 effect on decaying bodies as on phosphuretted hydrogen, the spon- 

 taneous inflammability of which they destroy. 



Many bodies which do not decay when moistened with water, 

 enter into eremacausis when in contact with an alkali. Gallic 

 acid, hsematin, and many other compounds, may be dissolved in 

 water and yet remain unaltered ; but if the smallest quantity of a 

 free alkali is present, they acquire the property of attracting oxy- 

 gen, and are converted into a brown substance like humus, evol- 

 ving very frequently at the same time carbonic acid. (Chevreul.) 



A very remarkable kind of eremacausis takes place in many 

 vegetable substances, when they are exposed to the influence of 

 air, water, and ammonia. They absorb oxygen very rapidly, and 

 form splendid violet or red-colored liquids, as in the case of orcin 

 and erythrin. They now contain an azotized substance, not in 

 the form of ammonia. 



All these facts show that the action of oxygen seldom affects 

 the carbon of decaying substances, and this corresponds exactly 

 to what happens in combustion at high temperatures. It is well 

 known, for example, that when no more oxygen is admitted to a 

 compound of carbon and hydrogen than is sufficient to combine 

 with its hydrogen, the carbon is not burned, but is separated as 

 lamp-black ; while, if the quantity of oxygen is not sufficient even 

 to consume all the hydrogen, new compounds are formed, such 

 as naphtha! in and similar matters, which contain a smaller pro- 



