The Influence of Changes in Concentration and Temperature upon the Bactericidal Activity of Formaldehyde in Aqueous Solutions
Although formaldehyde in aqueous solution (formalin) is an important and widely used disinfectant, there is very little information available concerning the exact effect of changes in either concentration or temperature upon its bactericidal activity. An experimental study was therefore made of the bactericidal activity of formaldehyde. This study was conducted along the lines of previous studies of the bactericidal activities of phenols and alcohols (Tilley, 1939, 1942).
An Experimental Study of the Relation between Concentration of Disinfectants and Time Required for Disinfection
The mechanism of disinfection has been studied by a considerable number of investigators but most of the published work, and especially that concerning the relation between concentration of disinfectant and time required for disinfection, was done many years ago. It seemed worth while, therefore, to make a further study of this phase of the subject, with special reference to the possible practical utility of mathematical formulas. An excellent discussion of the mechanism of disinfection, with reference to the literature, is contained in the treatise on Physiology and Biochemistry of Bacteria, by Buchanan and Fulmer (1930) and no attempt will be made here to review the literature. In the present work the equation Cnut = a constant (A) has been assumed to be the basic equation for the mechanism of disinfection. This equation was employed by Watson (1908) without details regarding its ultimate derivation. Buchanan and Fulmer have shown that it may be derived from the Guldberg-Waage law. Obviously its practical application presupposes strict uniformity in all experimental conditions and in all factors other than disinfectant concentration (C) and disinfection time (t). The writer has determined the bactericidal efficiencies of several phenols and alcohols by a modified Rideal-Walker technic and from the experimental data thus obtained has calculated values of the concentration exponent (n) for these disinfectants. Calculation is facilitated by expression of the equation Cn. t = A in
Germicidal Efficiency of Coconut Oil and Linseed Oil Soaps and of Their Mixtures with Cresol
While investigating soap-cresol solutions made with different kinds of soap, we found that preparations made with coconut oil soap exhibited much greater germicidal activity against B. typhosus than preparations made with linseed oil soap, which is the soap usually employed at the present time. This led us to make a more extended study of the germicidal value of these soaps and of their mixtures with cresol, some of the results of which are presented in this paper. Our work consisted in part of an investigation of the germicidal value of the soaps of the pure fatty acids of the saturated series from butyric to palmitic, inclusive. As the results obtained were similar to those of Reichenbach 1 and of Walker,2 we shall not discuss them in detail, but state only that they show that the germicidal value of the soaps of the saturated fatty acids increases regularly with increasing molecular weight. The results which we shall present here are mainly those which seem to us to have practical value in demonstrating the value of coconut oil soap and preparations containing coconut oil soap.