148 DISINFECTION AND STERILIZATION 



containing them have been put on the market. Creolin is 

 one which is very much used in veterinary practice and forms 

 a milky fluid with water, while lysol forms a clear frothy 

 liquid. Both of these appear to be more active than carbolic 

 acid and are less poisonous and more agreeable to use. 

 They are used in 2 to 5 per cent, solution. 



Alcohol. — Ordinary (ethyl) alcohol (C2H6OH) is largely 

 used as a preservative, also as a disinfectant for the body 

 surface, hands, and arms. Experiments show that. alcohol 

 of 70 per cent, strength is most strongly bactericidal and 

 that absolute alcohol is very slightly so. 



Soap. — Experimenters have obtained many conflicting 

 results with soaps when tested on different organisms, as 

 is to be expected from the great variations in this article. 

 Miss Vera McCoy in the author's laboratory carried out 

 experiments with nine commercial soaps — Ivory, Naphtha, 

 Packer's Tar, Grandpa's Tar, Balsam Peru, A. D. S. Car- 

 bolic, German Green, Dutch Cleanser, Sapolio — and ob- 

 tained abundant growth from spores of Bacterium anthracis, 

 from Bacillus coli and from Micrococcus pyogenes aureus in 

 all cases even when the organisms had been exposed twenty- 

 four hours in 5 per cent, solutions. From these results and 

 from the wide variations reported in the literature it is clear 

 that soap solutions alone cannot be depended on as dis- 

 infectants. Medicated soaps do not appear to offer any 

 advantages in this respect. 



Formaldehyde. — F6rmaldehyde (HCHO) is perhaps the 

 most largely used chemical disinfectant at the present time. 

 The substance is a gas but occurs most commonly in com- 

 merce as a watery solution containing approximately 40 

 per cent, of the gas. This solution is variously known as 

 formalin, formol, and formaldehyde solution. The first two 

 names are patented and the substance under these names 

 usually costs more. It is used in the gaseous form for disin- 

 fecting closed spaces of all kinds to the exclusion of most 

 other means today. A great many types of formalin gen- 

 erators have been devised. The gas has little power of 

 penetration and all material to be reached should be exposed 

 as much as possible. The dry gas is almost ineffectiAe, so 



