Effect of the replacement of oxygen with sulphur in the cresol molecule on toxicity to goldfish

Summary

A study was made of the toxicity of the three tolyl mercaptans with respect to concentration and survival time at 27 °C, and the results were compared with each other, as well as with phenol, rotenone, and the corresponding cresols. Goldfishes of the same lot, each weighing 6.0 to 7.5 g., were used as the test animals.

The type of toxic action of the tolyl mercaptans was found to be similar to that of phenyl mercaptan, but different from that of the corresponding cresols.

According to the minimum product of concentration and survival time, which measures toxicity at its range of most powerful action,m-tolyl mercaptan is the least toxic of the isomers. It is about four times as toxic, the ortho compound is nearly five times as toxic and the para compound is about eight and one-half times as toxic as phenol. Rotenone is about 85, 70, and 40 times as toxic as the respective mercaptans.

Compared according to the same criterion, the tolyl mercaptans bear the following ratios of toxicity: meta, 1.00; ortho, 1.19; and para, 2.19. These are practically the same relationships as were found for the corresponding cresols.

Essentially the same relationships are shown by other methods of comparison of the same data, which express relative toxicity under conditions in the neighborhood of its maximum power with respect to concentration and time. Methods emphasizing the effect of the threshold of toxicity, however, lead to greater expansion of the toxic ratios.

The replacement of the oxygen atom of the cresol molecule with sulphur causes a fourfold increase in toxicity. A similar chemical relationship in the phenyl homologues, however, has been found in a previous study to correspond to a sevenfold difference in toxicity to goldfish of much smaller size.