EREMACAUSIS. 7 13 



number are affected by that element; the various essential 

 and fixed oils absorb oxygen in different degrees, the first 

 becoming resins and the second acquiring the drying pro- 

 perties of varnishes ; the essential oil of bitter almonds is gra- 

 dually converted into benzoic acid, and the vapour of ether 

 passes slowly into acetic acid, while white indigo and other 

 colouring principles undergo remarkable changes from a rapid 

 absorption of oxygen. The direct oxidation of alcohol and 

 ether, which gives rise to acetic acid, is greatly favoured by the 

 contact of spongy platinum. The highly oxygenised acids act 

 with much more energy upon organic compounds and give rise 

 to various products according to the quantity of oxygen com- 

 municated. Thus alcohol is converted by oxidating matters, 

 into acetal, aldehyde, acetic acid, formic acid, oxalic acid, car- 

 bonic acid and water. In these reactions, the oxygen is fre- 

 quently observed to affect the hydrogen exclusively, which is 

 converted into water, while a quantity of oxygen exactly equi- 

 valent to the hydrogen thus withdrawn, enters into combination 

 with the remaining elements, and appears to be substituted for 

 the hydrogen. Thus by the action of four atoms of oxygen, 

 upon one atom of alcohol C 4 H 5 O + HO, two atoms of hydrogen 

 are withdrawn as water, while two atoms of oxygen are at the 

 same time absorbed by the remaining elements of the alcohol, 

 which becomes hydrated acetic acid C 4 H 3 O 3 + HO. When 

 anhydrous sugar C 12 H 9 O 9 is treated with hypermanganate of 

 potash, the nine atoms of hydrogen which the former contains 

 are replaced by nine atoms of oxygen, and six atoms of oxalic 

 acid formed 6'C, 2 O 3 . 



The presence of water greatly promotes the action of the 

 oxygen of the atmosphere upon organic substances. The name 

 eremacausis has been applied by Liebig to the slow combustion 

 or oxidation of organic matters in air. Vegetable juices eva- 

 porated by a gentle heat in air allow a brown or brownish black 

 substance to precipitate, known as extractive matter, and similar 

 in properties from whatever juice it is formed. It is insoluble 

 or very sparingly soluble in water, but dissolved with facility by 

 alkalies. By the action of air upon solid animal or vegetable 

 matters, a similar pulverulent brown substance is formed known 

 as humus. According to an observation of De Saussure, the 

 sawdust of oak wood converts oxygen into carbonic acid, without 



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