190 



PRINCIPLES OF DISINFECTION 



sublimate and to a 5 per cent, solution of carbolic acid. The 

 antiseptic value of formalin is very high, and it will inhibit the 

 growth of bacteria if present in a proportion of 1 to 25 to 50,000; 

 for germicidal purposes a J per cent solution should be employed. 



When formaldehyde was first introduced as a disinfectant it was 

 used by allowing the gas to evaporate unaided from the watery 

 solution. This is a slow process, requiring long exposures and large 

 amounts of formalin to be in any way effective. Later, Trillat devised 

 a method, using a lamp of his own construction, in which methyl- 

 alcohol was evaporated under conditions that oxidized it into formal- 

 dehyde; but since the yield was only 7 to 8 per cent, of the methyl- 

 alcohol used, this process was expensive, slow, and not very efficient. 

 Other arrangements allow the evaporation of formalin with such 

 additions (20 per cent, chloride of calcium-glycerin) that the forma- 

 tion of paraform is prevented. Still other devices are based upon 

 the heating and decomposition of paraform into formaldehyde. 



Fio. 108 



Breslau regenerator and lamp. 



According to Gotschlich, the best formaldehyde disinfecting pro- 

 cedure is that of Fliigge and his assistants. It is known as the Breslau 

 method, and consists in evaporating a dilute formalin (1 part of for- 

 malin to 4 parts of water) in a simple apparatus. It has been found 

 that such dilute formalin solutions do not upon evaporation form 

 paraform, but allow all the formaldehyde present in solution to be 

 expelled with the evaporating water. Harrington recommends very 

 highly a formalin disinfecting apparatus devised by Professor Robin- 

 son, of Bowdoin College; also a regenerator made by the Sanitary 

 Construction Company, which is said to be simple and economical. 

 Paraform evaporation is brought about by the Schering paraform 

 lamp. 



Before using any of the apparatus mentioned, and formaldehyde 



