The Toxicity of the Double Chlorides of Mercury and Sodium: I. Experiments with the Minnow Phoxinus Phoxinus (L.) Available to Purchase

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.