32 MICRO-ORGANISMS AND FERMENTATION. 



It is an established rule that two disinfectants should not 

 be used simultaneously, or one immediately after the other, 

 especially if their composition is unknown ; otherwise there 

 is danger that they may neutralise each other's action. Thus, 

 chloride of lime and calcium bisulphite should never be used 

 at the same place. 



The literature of antiseptics used in the industry Will, 

 Lindner, Brand, Schonfeld, etc. has grown to considerable 

 proportions. A short resume of the methods of application 

 of the respective substances follows. 



Ammonium fluoride, especially the acid salt, has a very 

 wide application, owing to its great antiseptic power. It is 

 a crystalline powder, readily soluble in water. In the pure 

 condition it contains about 35 per cent, of hydrofluoric acid ; 

 the commercial product, however, contains a less quantity, 

 and sometimes not more than 20 per cent. It is used for the 

 treatment of pipes, vats, etc. Pipes are filled with a solution 

 containing about 0-5 per cent. In rinsing out vats a 3 to 5 per 

 cent, solution must be used. Ammonium fluoride is not 

 suitable for the treatment of metal, as it slowly attacks it. 

 After treatment, a very thorough washing with water is 

 necessary. 



Formalin has also been very largely applied in practice. 

 It is an aqueous solution of formaldehyde (40 per cent, by 

 volume or 37-2 per cent, by weight), and it forms one of the 

 most powerful antiseptics. As it does not attack metal, it 

 can be applied more generally than the fluorides. It may be 

 used in the form of gas by soaking cotton wool or cloths in 

 formalin, and hanging them up in the area to be disinfected, 

 or it may be applied in specially constructed lamps, in which, 

 by the imperfect combustion of methyl alcohol, formaldehyde 

 is produced. The most frequent and most successful method 

 of application is, however, to dilute formalin with water, and 

 apply it as a spray to the walls of vats, etc. A solution of 

 0-5 per cent, of formaldehyde (about 1| litres of the commercial 

 article to 100 litres of water) is most generally applicable. 

 The vessel must then be well rinsed with water, and if the 

 odour cannot be got rid of, ammonia may be applied. 



Chloride of lime has been used for many years, on account 



