THE KINETICS OF PENETRATION : XII. HYDROGEN SULFIDE.

The rate of entrance of H(2)S into cells of Valonia macrophysa has been studied and it has been shown that at any given time up to 5 minutes the rate of entrance of total sulfide (H(2)S + S(-)) into the sap is proportional to the concentration of molecular H(2)S in the external solution. This is in marked contrast with the entrance of ammonia, where Osterhout has shown that the rate of entrance of total ammonia (NH(3) + NR(4) (+)) does not increase in a linear way with the increase in the external concentration of NH(3), but falls off. The strong base guanidine also acts thus. It has been shown that the rate of entrance of H(2)S is best explained by assuming that it enters by diffusion of molecular H(2)S through the non-aqueous protoplasmic surface. It has been pointed out that the simple diffusion requires that the rate of entrance might be expected to be monomolecular. Possible causes of the failure of H(2)S to follow this relationship have been discussed.