DECOMPOSITION OP OttOANlC COMPOUNDS. 457 



One of the fermentations in which oxygen takes part is acetic acid fermen- 

 tation, resulting in the conversion of alcohol into acetic acid by oxidation. 

 This conversion may be brought about by suitable oxidizing agents, or even by 

 atmospheric oxygen, and is then practically a slow combustion or decay. But 

 the transfer of oxygen may be brought about by micro-organisms and the pro- 

 cess is then defined as fermentation. 



Whenever organic bodies (a dead animal, for instance) undergo de- 

 composition in nature, the processes of fermentation and putrefaction 

 are generally accompanied by oxidation or decay. 



The conditions under which a substance will ferment or putrefy 

 have been stated above, and the non-fulfilment of these conditions 

 enables us to prevent decomposition artificially. 



Thus, we make use of a low temperature in our refrigerators or by 

 cold storage. We expel water by drying or by dehydrating agents 

 such as absolute alcohol. We prevent the action of the ferments 

 either by antiseptic agents (salt, carbolic or salicylic acid, etc.) which 

 are incompatible with organic life, or by excluding the air, and with 

 it the ferments, by enclosing the substances in air-tight vessels (glass 

 jars, tin cans, etc.), which, when filled, are heated sufficiently to destroy 

 any bacteria which may have been present. 



Antiseptics and disinfectants. While the term antiseptics is 

 applied to those substances which retard or prevent fermentation and 

 putrefaction, the term disinfectants refers to those agents actually 

 destroying the organisms which are the causes of these decomposi- 

 tions. If we assume that all infectious diseases are due to micro- 

 organisms, or germs of various kinds, disinfectants may be considered 

 as equivalent to germicides. Disinfectants are generally antiseptics 

 also, but the latter are not in all cases disinfectants. The solution 

 of a substance of certain strength may act as a disinfectant and 

 antiseptic, while the same solution diluted further may act as an 

 antiseptic only, but not as a disinfectant. 



Deodorizers are those substances which convert the strongly smell- 

 ing products of decomposition into inodorous compounds. Strong 

 oxidizing agents are generally good deodorizers, as, for instance, 

 chlorine, potassium permanganate, hydrogen dioxide, etc. Among 

 the best antiseptics and disinfectants are mercuric chloride (a solution 

 of 1 : 500 or 1 : 1000) ; carbolic acid (5 per cent, solution) ; potassium 

 permanganate (5 per cent, solution) ; chlorine (generally used in the 

 form of a 4 per cent, solution of calcium hypochlorite) ; formaldehyde, 



