146 DISINFECTION AND STERILIZATION 



COMPOUNDS. 



Calcium Oxide. — Calcium oxide (CaO), quick lime, is an 

 excellent disinfectant for stables, yards, outhouses, etc., 

 where it is used in the freshly slaked condition as "white 

 wash;" also to disinfect carcasses to be buried. It is very 

 ejfScient against the typhoid bacillus in water, where it is 

 much used to assist in the softening. 



Chloride of Lime. — Chloride of lime, bleaching powder, 

 which consists of calcium hypochlorite, the active agent, 

 and chloride and some unchanged quicklime is one of the 

 most useful disinfectants. It is employed to sterilize water 

 for drinking purposes on a large scale and to disinfect sewage 

 plant effluents. A 5 per cent, solution is the proper strength 

 for ordinary disinfection. Only a supply which is fresh or 

 has been kept in air-tight containers should be used, as it 

 rapidly loses strength on exposure to the air. The active 

 agent is nascent oxygen liberated from the decomposition of 

 the hypochlorite. 



Sodium Hypochlorite. — Sodium hypochlorite prepared by 

 the electrolysis of common salt has been used to some extent. 



Bichloride of Mercury. — Bichloride of mercury, mercuric 

 chloride, corrosive sublimate (HgCU), is the strongest of all 

 disinfectants under proper conditions. It is also extremely 

 poisonous to men and animals and great care is necessary 

 in its use. It is precipitated by albuminous substances and 

 attacks metallic objects, hence should not be used in the 

 presence of these classes of substances. 



It is used in a strength of one part HgCU to 1000 of water 

 for general disinfection. Ammonium chloride or sodium 

 chloride, common salt, in quantities equal to the bichloride, 

 or citric acid in one-half of the amount should be added in 

 making large quantities of solution or for use with albumin- 

 ous fluids to prevent precipitation of the mercury (Fig. 108). 



None of the other metallic salts are of ^■alue as practical 

 disinfectants aside from their use in surgical practice. In 

 this latter class come boric acid, silver nitrate, potassium 

 permanganate. The strong mineral acids and alkalis are, 

 of course, destructi\'e to bacteria, but their corrosive effect 



