The Germicidal Power of Some Alcohols for Bacterium Typhosum and Staphylococcus Aureus, and Its Relation to Surface Tension *

It is a matter of common knowledge that the phenol coefficients of most organic disinfectants vary with the length of the alkyl chain that may be present or introduced into the molecule. As a rule, the germicidal power against both common test organisms, Bacterium typhosum and Staphylococcus aureus, increases with increasing length of the alkyl chain up to a point determined by the lack of solubility of the substance. Tilley and Schaffer have published accurate data on the phenol coefficients of numerous germicides, and have introduced the term "molecular coefficient," a value defined as molecular weight substance tested . -~~~~~~~X phenol coefficient. molecular weight phenol By the use of this coefficient they were able to show that there was a regular increase in the action of most of the experimental substances against both of the test organisms. For the primary alcohols, in going from one compound to the next, this rate of increase was quite constant and equal to 3.36, although methyl alcohol did not conform to the rule in its action against the typhoid bacillus, while both methyl and ethyl failed against the staphylococcus. For the secondary and tertiary alcohols the rates were about 3.0 and 2.7, respectively. Since increasing length of alkyl chain tends to increase the surface activity, the relation of surface tension to germicidal power has been studied by several workers. In brief, Christiansen showed that with methyl, ethyl, and propyl alcohols the two qualities varied with one another, and that when killing occurred in a short time (30 seconds) the surface tension was about 0.4 that of water. Traube has made the statement that with the alcohols the ability to lower surface tension progresses in the ratio 1: 3: 32, etc., i.e., according to Traube's rule, and that the narcotic, disinfectant, and pharmacological powers proceeded pari passu. He pointed out, also, that while the primary and secondary alcohols had about the same surface energy, each for each, the tertiary compounds were less active, and