EREIVIACAUSIS OR DECAY. 323 



ulverulent brown substance is formed, and is known 



y the name of humus, 

 I The conditions which determine the commence- 

 [ment of eremacausis are of various kinds. Many 

 (organic substances, particularly such as are mixtures 

 pi several more simple matters, oxidize in the air 

 when simply moistened with water; others not until 

 jthey 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 decaying matters. 



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 substances, empyreumatic 

 oils, and oil of turpentine, possess a similar action 

 in this respect. The latter substances have the 

 same effect on decaying bodies as on phosphuretted 

 hydrogen, the spontaneous 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, haematin,* 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 oxygen, and are converted into a brown 

 substance like humus, evolving 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 sub- 

 stance, not in the form of ammonia. 



All these facts show, that the action of oxygen 

 seldom affects the carbon of decaying substances, 



^ The coloring matter of logwood. 



