STERILIZATION ANTISEPSIS FOOD PRESERVATION 77 



of albuminous combinations, thus allowing greater penetration 

 of the disinfectant. 



Many other substances closely related to carbolic acid are 

 used and possess marked germicidal properties. Among them 

 may be mentioned creolin, cresol and lysol. They are all slightly 

 superior to carbolic acid in actual germicidal value. 



Formalin is a 40 per cent aqueous solution of formaldehyde, 

 H 2 CO. Remarkable claims have been made for this substance, 

 and numerous investigations have shown it to possess, both in 

 the liquid and gaseous forms, wonderful disinfecting power under 

 certain conditions. Later investigations indicate that its germi- 

 cidal power had been somewhat overestimated. In solutions 

 of i-iooo an exposure of twenty-four hours is necessary to destroy 

 the staphylococcus pyogenes aureus, while 1-5000 is sufficient 

 to restrain its growth (Slater and Rideal). Its use in a gaseous 

 form as a house disinfectant is by far the most important applica- 

 tion at the present time. 



From 250 to 500 c.c. of formalin together with 500 to 1000 c.c. 

 of water should be vaporized for each 1000 cubic feet of air space 

 in the room, and the room should remain tightly closed for at 

 least four hours, preferably over night. Many methods of 

 vaporizing formaldehyde have been devised. Some form of 

 tank, provided with heating apparatus and with an outlet tube 

 which passes through the keyhole into the room, is perhaps the 

 most convenient where much disinfection has to be done. If 

 apparatus of this sort is not at hand, good results may be obtained 

 by putting the formalin and the water previously heated to boil- 

 ing, in a large pail in the center of the room, and then adding 

 rapidly crystalline potassium permanganate, about 200 grams to 

 each 500 c.c. of formalin used. The permanganate oxidizes 

 some of the formaldehyde and produces heat to evaporate the 

 rest of it. From 25 to 50 per cent more formalin should therefore 

 be used for a given air space. It is well also to add about 10 per 

 cent of glycerin to the water so as to raise the boiling-point some- 

 what and insure more complete vaporization of the formaldehyde. 



