Organic Disinfectants 215 



0.66 per cent, of chlorin) rapidly killed the tubercle bacillus 

 and i : 10 (equal to 3.3 per cent, chlorin) killed anthrax spores. 

 lodin Terchlorid (IC1 3 ). This compound, which is so unstable 

 that it only keeps in an atmosphere of Cl-gas, has great germi- 

 cidal action, that probably depends upon the readiness with which 

 it decomposes. In solutions of i : 1000 it kills vegetative bac- 

 teria in a few minutes, and in i : 100 it kills anthrax spores with 

 equal rapidity. The presence of organic and albuminous mate- 

 rials does not interfere with the germicidal action. 



Organic Disinfectants. 



Carbolic acid (C 6 H 5 OH) is the most important and generally useful 

 of these. It has the advantage of being cheap and easily kept 

 and handled. In the pure state it consists of colorless acicular 

 crystals. When exposed to the atmosphere it takes up water 

 and gradually becomes a brownish-yellow oily fluid. The 

 crystals and deliquesced crystals have powerful escharotic proper- 

 ties and cannot be touched without destruction of the skin. 

 In 2 to 3 or 5 per cent, solutions carbolic acid destroys most 

 bacteria within a few minutes. Anthrax and other powerfully 

 resisting spores, however, require prolonged exposure. Tetanus 

 spores are said not to be killed in less than fifteen hours. There 

 is no ionization ; the reagent seems to act by coagulating the bac- 

 terial protoplasm. 



Though carbolic acid has been for a quarter of a century a 

 favorite surgical disinfectant, the application of 5 per cent, 

 solution to the skin has so frequently caused gangrene that it is 

 at present in some merited disfavor. 



Closely related to carbolic acid and other products of coal-tar 

 distillation are orthocresol, metacresol, and paracresol. " Tri- 

 kresol," a much used antiseptic, is a commercial product con- 

 sisting of a mixture of all three of the cresols. It is more strongly 

 germicidal than carbolic acid, but is less soluble in water. It is 

 or has been largely used for addition to therapeutic serums in 

 the proportion of 0.4 per cent, as an antiseptic. Such addition 

 causes the formation of an albuminous precipitate in which, 

 doubtless, much of the antiseptic is lost, for upon its removal or 

 even upon its sedimentation resisting forms of bacteria may 

 grow in the serum. It cannot, therefore, be looked upon as a 

 reliable preservative. 



"Lysol" is said to be a solution of coal-tar cresol in potassium 

 soap. It has the advantage of forming a lather-like soap, so 

 that it can be employed both as a cleanser and disinfectant. In 

 i per cent, solutions it is capable of destroying cocci, typhoid 

 bacilli, and other micro-organisms of low resisting power. 



"Creolin" is also a combination of cresols with potassium 

 soap. When added to water it immediately forms an emulsion. 

 It has been much used in obstetric practice, where it has earned 

 more reputation than it deserves. 



''Formalin." This is Schering's commercial denomination of a 

 30 to 40 per cent, aqueous solution of formaldehyd gas (H COH) 

 or formic aldehyd. The solution is highly germicidal so 

 long as it is fresh. When exposed for long to the atmosphere 

 it polymerizes into trioxymethylene and paraformaldehyde 

 and greatly loses its power. A 10 per cent, solution of formalin 

 kills pus cocci in half an hour. A 5 per cent, solution kills cholera 

 spirilli in three minutes; anthrax bacilli, in fifteen minutes; 

 anthrax spores, in five hours. Pure formalin kills anthrax spores 



