The Influence of Certain Inorganic Salts on the Germicidal Activity of Hydrogen Peroxide

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Abstract
The germicidal activity of H2O2 on Escherichia coli and on Staphylococcus aureus is greatly increased by the combined presence of ferric and cupric sulphates. The optimum concentrations were found to be approximately 0.1 millimol of each of the metallic ions per 120 cc. of solution. The influence of these salts on the toxicity of H2O2 is not altered by presence of cellulose, but is slightly decreased in presence of proteins. Potassium dichromate, when promoted with manganous or cobaltous sulphate, was found to increase the toxicity of H2O2 for E. coli approximately as much as the ferric and cupric sulphates. The effects of potassium dichromate with manganous sulphate and potassium dichromate with cobaltous sulphate were measured at only 0.1 millimol of the dichromate and metallic ion per 120 cc. of solution. The phenol coefficients of H2O2 as measured in relation to E. coli and Staph. aureus were 0.014 and 0.012, respectively, but in presence of optimum concentrations of cupric and ferric sulphates they were increased to 1.4 and 1.2; while 0.1 millimol of dichromate ions in 120 cc. of solution in presence of the same concentration of cobaltous or manganous ions increased the phenol coefficient of H2O2 as measured on E. coli to 1.4. Since the salts which catalyze and promote decomposition and increase oxidizing property of H2O2 all increase its germicidal activity, it seems logical to conclude that the toxicity of H2O2 is dependent on its ability as an oxidizing agent.