294 CONSIDERATION OF CARBON COMPOUNDS. 



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 chlorine (generally used in 

 the form of a 4 per cent, solution of hypochlorite of calcium), mer- 

 curic chloride (a solution of 1 : 500 or 1 : 1000), carbolic acid (a 5 per 

 cent, solution), and some other substances. 



Action of chlorine and bromine. These two elements act upon 

 organic substances (similarly to oxygen) in three different ways, viz., 

 they either (rarely, however) combine directly with the organic sub- 

 stance, or remove hydrogen, or replace hydrogen. The following 

 equations illustrate this action : 



C 2 H 4 + 2Br C 2 H 4 Br 2 . 



Ethylene. Bromine. Ethylene bromide. 



C 2 H 6 O + 2C1 : : C 2 H 4 + 2HC1. 

 Ethyl alcohol. Chlorine. Aldehyde. Hydrochloric acid. 



C 2 H 4 O 2 + 2C1 C 2 H 3 C10 2 + HC1. 



Acetic acid. Chlorine. Monochloracetic Hydrochloric 



acid. acid. 



In the presence of water, chlorine and bromine often act as oxidiz- 

 ing agents by combining with the hydrogen of the water and liber- 

 ating oxygen ; iodine may act in a similar manner as an oxidizing 

 agent, but it rarely acts directly by substitution. 



Action of nitric acid. This substance acts either by direct com- 

 bination with organic bases forming salts, or as an oxidizing agent, 

 or by substitution of nitryl, NO 2 , for hydrogen. As instances of the 



