254 AIDS TO BACTERIOLOGY 



dopper sulphate in a proportion of 1 part per million 

 has been used for the destruction of algse in reservoirs. 

 Bordeaux mixture, a popular insecticide for plants, is 

 a mixture of calcium hydrate and copper sulphate. 

 Springer finds that copper salts are highly selective, 

 being most efficient in inhibiting the action of putre- 

 factive organisms. 



Oxidising Disinfectants. The halogens (pp. 242, 251) 

 are examples of oxidising agents. The permanganates 

 have considerable germicidal power when in strongly 

 acid or alkaline solution, but the readiness with which 

 they are affected by organic substances makes them 

 unreliable for practical use. Peroxides and ozone are 

 open to the same objection, and have less disinfectant 

 power. 



While ozone is a deodoriser, it masks rather than destroys 

 smells. Hill and Flack found that one part in a million 

 irritates the respiratory tract, and even less reduces 

 respiratory metabolism, and rapidly causes a fall of body 

 temperature. They describe its beneficial effect, as 

 popularly believed in, as a myth, and think the irritation 

 of the olfactory nerves may relieve the monotony of close 

 air. Ozone may conceal faults in ventilation when used 

 for removing frowsiness in the atmosphere of a closed 

 place. 



Hydrogen peroxide has been used as a milk and cream 

 preservative (p. 221). Hinks (Analyst, December, 1915) 

 has shown that it persists in such material for months, 

 and does not, as might be thought, quickly break up in 

 the presence of organic matter. It is used for bleaching 

 purposes, as a mouth-wash, and as lotion for infected 

 or suppurating wounds. It is non-toxic, practically 

 non-irritant, and does not precipitate albumen, but a 

 free exit must exist for the escape of the oxygen, which 

 is so rapidly liberated when the peroxide comes into 

 contact with blood or pus. A small quantity of mineral 

 acid or acetanilide is added to render it more stable. 



Disinfectants of the Aliphatic Series. Formaldehyde is 

 supplied either in the form of a 40 per cent, solution 

 (formalin) or as solid para-formaldehyde. As a gaseous 

 disinfectant little more than superficial disinfection is 

 possible. Disinfection is best insured by saturation of 

 the air with moisture, maintenance of a good room- 



