146 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 owing to the presence of soap. 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 (C2H5OH) 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 obtained 

 abundant growth from spores of Bacillus anthracis, from 

 Escherichia coli and from Staphylococcus 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 he depended on as disinfec- 

 tants. Medicated soaps do not appear to offer any advan- 

 tages in this respect. The amount of the disinfectant which 

 goes into solution when the soap is dissolved is too small to 

 have any effect. 



Formaldehyde.— Formaldehyde (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 

 usuall}^ 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 



