Evidence has been brought forward to show that a large number of simple organic compounds produce toxic symptoms in living organisms when they reach a definite concentration in some biophase. If this is so, for non-associated compounds which do not participate in hydrogen-bonding the equation — log10Ct = – log10C′ + k[P] is suggested by considerations of solubility. Here, Ct and C′ are the toxic concentrations in water and in the biophase respectively (g.-mol./1.); [P] is the parachor (c.c.) and k is a constant. This equation was found to hold and examples are given. The constant k has been found to have the value o·012 and C′ is, of course, constant for any one manifestation of toxicity. Corrections can be applied for the presence in the molecules of the toxic compounds of groupings giving rise to association and hydrogen bonding.
The equation is useful for the prediction of toxicities of compounds which would be expected to be physically toxic and for the classification of data on toxicities of aqueous solutions.