THE EFFECTS OF ELECTROLYTES ON GELATIN AND THEIR BIOLOGICAL SIGNIFICANCE. III. THE EFFECTS OF MIXTURES OF SALTS ON THE PRECIPlTA- TION OF GELATIN

In two previous papers, the writer described the effects of acids, alkalies, and salts,’ and the effects of combinations of salts with acids and alkalies* on the precipitation of gelatin by alcohol. In a preliminary paper,” a brief account was given of antagonism observed between different salts in gelatin, these results being of particular interest to the biologist from the point of view of the antagonism found between various salts in their effects upon organisms. The present paper deals in more detail with the effect of mixt,ures of salts upon gelatin from this point of view. If the experiments with gelatin are to be used as a basis for general conclusions, it is absolutely necessary in determining the effect of one salt upon another to combine them in all possible concentrations. It is not enough to know that 0.5 M CaClz decreases the effect of 0.5 M NaCl; the effect of higher or lower concentrations of CaClz upon either higher or lower concentrations of NaC1 may be, and usually is, quite different. This failure to use a sufficiently representative series of concentrations of the salts is largely responsible, in the writer’s opinion, for some of the conflicting results obt,ained in antagonism experiments. In regard to the biological work which has been done on salt antagonism the following brief statement must suffice. Loeb4 has