The Toxicity of the Double Chlorides of Mercury and Sodium

ABSTRACT Mercuric chloride, one of the most toxic of inorganic substances, does not ionize in aqueous solution, but in the presence of sodium chloride forms the double chlorides NaHgCl3 and Na2HgCl4 which ionize readily. It has been variously claimed that the ionization of mercuric chloride, thus effected, is accompanied by an increase of toxicity, by a decrease of toxicity, or that the toxicity of the solution remains unaltered. In an investigation of the toxicity of mixed solutions of HgCl2 and NaCl to the minnow, Phoxinus phoxinus (L.), it is found that the addition, to HgCl2 solutions, of sufficient NaCl to convert the whole of the HgCl2 into the double chloride Na2HgCl4, and even ten times this quantity of NaCl effects no marked change in the toxicity of the solution. On the addition of a considerable excess of NaCl a marked prolongation of the survival time occurs, the maximum antagonistic effect being evident when the solution is approximately isotonic. Almost exactly the same result is obtained if the NaCl is replaced by quantities of glucose sufficient to effect equal changes in the osmotic pressure of the solutions, and thus the antagonistic action of the sodium chloride appears to be due to the physical, rather than the chemical, changes its addition brings about in the nature of the toxic solution.