STUDIES ON SALT ACTION IX. THE ADDITIVE AND ANTAGONISTIC EFFECTS OF SODIUM AND CALCIUM CHLORIDES UPON THE VIABILITY OF BACT. COLI

Abstract

In the immediately preceding paper of this series (Winslow and Falk, 1923) we have presented in some detail the results of our studies upon the influence of two salts with a common anion, one with a typical monovalent and one with a typical divalent cation, upon the viability of Bact. coli in water. It was there shown that at any pH value 0.725 M NaCl and 0.435 M CaCl2 solutions are toxic to this organism and that 0.145 CaCl2 is toxic in an alkaline solution (pH 8.0), its toxicity here being due to the fact that CaCl2 under such conditions inhibits the ability of the bacteria to regulate the reaction of the solution. Over four years ago (Winslow and Falk, 1918) we presented a preliminary report which indicated that in a solution containing sodium and calcium salts in appropriate proportions an antagonistic action may be manifest which tends to protect the bacteria against the toxic action which would be exerted by each salt if present alone. The experiments here reported deal with this question, the technique being the same as that reported in the paper first cited (Winslow and Falk, 1923). A solution of calcium chloride of 0.145 M strength, the strength at which toxic action first appears in an unadjusted alkaline solution, was chosen for the study of antagonism and in table 1 are presented the results of 21 tests in solutions of calcium chloride of this strength plus various concentrations of sodium chloride. The solution was made up alkaline (about pH 8.0) but was not adjusted thereafter and changes in reaction were not recorded. 237