THE DESTRUCTION OF BACTERIA 107 



tended, clothing, bed-linen, and fabrics should be spread out, cup- 

 boards and drawers freely opened. The cracks of windows and 

 doors should be hermetically sealed with paper strips or by calking 

 with cotton. In all cases moisture should be provided for, either 

 in the generating apparatus or by a separate boiler. 



Direct evaporation of formaldehyd from formalin solutions has 

 been the principle underlying most of the methods. If such evapora- 

 tion is attempted from an open vessel, however, polymerization of 

 formaldehyd to the solid trioxymethylene occurs. To prevent this, 

 Trillat 68 and others have constructed special autoclaves in which 20 per 

 cent of calcium chlorid is added to formalin which is then vaporized 

 under pressure. 



The Trillat autoclave, as well as others constructed on the same principle, 

 consists of a strong copper chamber of a capacity of about a gallon, fitted 

 with a cover which can be tightly screwed into place. The cover is perforated 

 by an outlet vent, a pressure gauge, and a thermometer. The whole apparatus 

 is adjusted upon a stand and set over a kerosene lamp. Into the chamber 

 is put about one-half to three-quarters its capacity of 40 per cent formaldehyd 

 (commercial formalin) containing 15-20 per cent calcium chlorid. The solu- 

 tion used should be free from methyl alcohol, since this leads to the formation, 

 with formaldehyd, of methylal, which is absolutely without germicidal action, 

 for a room of about 3,000 cubic feet Trillat advises the continuance of the 

 gas flow for about an hour. The method is not uniformly reliable. 



A method which has found much favor is that in which glycerin 

 usually in a concentration of 10 per cent is added to formalin. 

 According to Schlossmann 69 the presence of glycerin hinders poly- 

 merization. An apparatus in which this mixture is conveniently 

 utilized is that of Lentz. Formalin with 10 per cent glycerin is 

 placed in the copper tank and heated by a burner. This apparatus 

 has been favorably endorsed by the War Department of the United 

 States. 



The so-called Breslau method of generating formaldehyd depends 

 upon the evaporation of formaldehyd from dilute solutions, v. 

 Brunn 70 claims that where formalin in 30 to 40 per cent strength 

 is evaporated, water vapor is generated more rapidly than formal- 

 dehyd is liberated, and a concentration leading to polymerization 



* Trillat. Compt. rend, de 1'acad. dcs sc., 1896. 

 99 Schlossmann, Munch, med. Woch., 45, 1898 

 70 v. Brunn, Zeit. f . Hyg., xxx, 1899. 



