i9o8] POND— SOLUTION TENSION AND TOXICITY 252 



hydrolytic dissociation in any close way, tliough it is true that all of 

 the hydrolytcs in the tests I have made are more toxic than any of the 

 neutral salts. 



The fact that the h\ drolytes themselves are potent in saponification 

 has long been known, in fact the degree of hydrolysis has been meas- 

 ured by the rate of the saponification of esters. '^ Such salts have also 

 been found to be potent in the inversion of sugars."* It was supposed 

 that the inverting or saponifying power is associated with hydrolytic 

 dissociation, the H or the OH ions being the active agents. Ley'^ 

 (p. 214), however, found that KCl can invert sugar, so that other ions 

 than those resulting from hydrolytic dissociation are potent. Thus 

 it seems that exceptions arise to intercept the formulation of any 

 generalization. 



Significant also is the fact that dilutions of silver and mercury so 

 great that tlie reaction is neutral as tested are capable of causing total 

 inhibition. On the other hand, solutions of the neutral salts which are 

 comparatively very concentrated are not inhibiting. Thus in Table 

 XIII, ;;//2048 of silver is totally inhibiting but not measurably acid. 

 In some cases we find that solutions of equal acidity are also equitoxic 

 (Tables VIII and IX especially). This relation, however, fails in 

 some cases (Tables X and XI) . Moreover, partial or total inhibition 

 may occur with the hydrolytes at dilutions too great to show acidity as 

 here tested. Thus copper and zinc in Table IX show partial inhibi- 

 tion at w/ 1 6384, which is neutral, and mercury at ;»/ 16384 in Table 

 XIII shows almost total inhibition without acidity, while silver in 

 Table XIII shows total inhibition in a neutral concentration of the salt. 



The relative toxicity changes as the concentration of the enzyme 

 changes, provided the difference is enough. Thus in Tables IX, XI, 

 and XII copper and zinc are equitoxic, but in Table XVI they are less 

 equal, and in Table XVII still less so with the increasing concentra- 

 tion of the enzyme. Similar variations were found in the tests with 

 ethyl butyrate (Pond, /. c. 276). 



13 Shields, John, Ucber Hydrolysis in wasserigcn Salzlosungcn. Zeitsch. 

 physikalische Chem. 12:167-187. 1893. 



mLong, J. H., On the inversion of sugar by salts. Jour. Amcr. Chem. Soc. 

 18:120-130. 1896. 



• 5 Ley, H., Studien uber die hydrolytische Dissociation der Salzlosungcn. 

 Zeitsch. physikalische Chem. 30:193-257. 1899. 



