DISINFECTION, STERILIZATION AND ANTISEPSIS. 251 



used germicides. It is usually employed in strengths of from 

 i to 5 per cent. A 3 per cent, solution will sometimes kill the 

 spores of anthrax after two days' exposure (see Bacillus anthra- 

 cis, Part IV.) . In the absence of spores the anthrax bacillus 

 is destroyed by a i per cent, solution in one hour. The less 

 resistant pus cocci are destroyed rapidly by a 2 per cent, solu- 

 tion. Combination with an equal proportion of hydrochloric 

 acid enhances the efficacy of carbolic acid to a marked extent. 

 This is due to the prevention of albuminous combinations, 

 thus allowing greater penetration of the germicide. 



McBryde* found that the admixture of lime to carbolic acid 

 lessened the germicidal potency of the latter. He furthermore 

 found that liquor cresolis comp., U. S. P., a liquid soap con- 

 taining 50 per cent, cresol, misciblein all proportions with water, 

 is a more potent germicide than carbolic acid. Liquor cres. 

 comp. made from cresol of high boiling-points is more potent 

 than that made of cresol of lower boiling-points. That made 

 with cresol of 187 to 189 C. is nearly one and one-half times 

 greater than carbolic acid. 



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. 



Aniline Dyes. Many of these substances, notably pyok- 

 tanin (methyl- violet), possess germicidal properties. Mala- 

 chite green is said to possess even greater germicidal value than 

 pyoktanin. Methylene-blue also possesses considerable germi- 

 cidal power. 



Formalin is a 40 per cent, aqueous solution of formaldehyde. 

 Results of the earlier investigations seemed to show that for- 

 maldehyde possessed remarkably high germicidal properties, 

 but 1 ater experiments have failed to corroborate these. In solu- 

 tions of i-iooo an exposure of twenty-four hours is necessary 



*Dept. Agr., Bu. An. In., Bui. 100. May 31. 1907. 



