Organic Disinfectants i8i 



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 properties 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 ex- 

 posure. 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 bacterial protoplasm. 



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

 surgical disinfectant, the application of s 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 dis- 

 tillation are orthocresol, metacresol, and paracresol. "Trikresol," a 

 much used antiseptic, is a commercial product consisting 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 pre- 

 cipitate 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 trioxmethylene 

 and paraformaldehyde and greatly loses its power. A 10 per cent, solu- 

 tion 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. Pur^ formalin kills anthrax spores in 

 ten to thirty minutes. Strong solutions are extremely irritating and 

 so not applicable in surgery. They are, however, of great use for 

 household disinfection. Formalin and formaldehyd gas find their chief 

 usefulness for the aerial disinfection of sick chambers and domiciles, 

 where they are either used as a spray or the gas evolved by chemical 

 means or by heat, as wiU be shown below. 

 Peroxid of hydrogen (H2O2) is germicidal through its power to liberate the 

 nascent O. It quickly decomposes when brought into contact with 

 organic matter, and, therefore, has a very limited sphere of usefulness. 



The following tables, compiled by Hiss from Fliigge,_ will show 

 the comparative values of the commonly employed antiseptics and 

 germicides: 



Certain fundamental principles govern the rationale of disin- 

 fection, and must be kept in mind: (i) the reagent employed should 

 be known to act destructively upon bacteria; (2) it must be applied 

 to the bacteria to be killed; (3) it must be applied in sufficiently con- 

 centrated form, and (4) it must be left in contact with the bacteria 

 long enough to accomplish the effect desired. 



During the period of illness the chamber in which the patient is 



