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 xr. PHYSIOLOGICAL ACTION OF THE IONS. i8i

poisons. It was found that potassium chlorate is poisonous, and this led to an investigation of the action of other potassium salts. Solutions of a definite strength were introduced into living organisms, and the degree of poisonousness was determined by the length of time required to kill the organism. The result of this investigation was to show that all potassium salts, with the exception, of course, of those containing a poisonous negative ion, like potassium cyanide, have nearly the same poisonous effect in solutions of equal concentration.

Eecently Kahlenberg (14) and Loeb (iJ), as well as Paul and Kronig (16), have investigated the action of salts on bacteria and spores. All the results obtained agree very perfectly with what would be expected from the dissociation theory. Paul and Kronig exposed spores for a certain length of time to the action of salt solutions at 18°, and determined the vitality of the spores by the number of bacteria colonies formed when placed under conditions favourable to their growth. The degree of dissociation of the following mercuric salts in equivalent solution decreases in the order given: chloride, bromide, thiocyanate, iodide, cyanide, and it was found that their powers of killing spores of the anthrax bacillus were in the same order, so that the cyanide has the least action. The influence of complex salts is still smaller, e.g. potassium mercuricyanide, K2(CN)4Hg, which gives hardly any mercuric ions. Similar relationships were found for gold and silver salts. By the addition of neutral salts, such as sodium chloride and potassium chloride, both the degree of dissociation and the poisonousness are diminished. In some other cases, for instance with acids, not only does the hydrogen ion exert a poisonous influence, but also the negative ion with which it is present, so that the action of hydrofluoric acid is greater than that of hydrochloric acid, although the latter is dissociated to the greater extent. Nevertheless, the weak acids, formic and acetic acids, have the smallest effect of any acids so far examined, whilst phenol shows peculiar relationships.

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