i9o8] 



POND— SOLUTION TF.NSION AND TOXICITY 



240 



for marked inhibition, and there is no evidence of chemical action 

 between the enzyme substance and the toxic salt. The cause of the 

 inhibition may be simply osmotic. In all of the remaining tests it 

 will be noted that the toxic salt solution has more or less acidity of its 

 own (due to hydrolytic dissociation) according to the dilution, and in 

 several cases the control acidity is greater than the sum of the enzyme 

 aciflity and of the reagent acidity. It seems, in some cases at least, 

 that there is chemical action between the substance of the enzyme 

 solution and the toxic salt which results in the liberation of acid. In 

 the higher dilutions of the toxic salt the acidity of the salt itself 

 approaches zero, and the acidity of the control tends to be identical 

 with that of the enzyme solution itself. Then again, at the point of 

 total inhibition the reagent acidity and the control acidity are often 

 equal. 



TABLE VIII: Cadmium and cobalt in conlemporaneous test 



CADMIUM 



COBALT 



1024. 

 512. 

 256. 

 128. 



64. 



32- 



0.03 

 0.06 

 0.08 



o. 10 



0.30 



o. 20 



0-33 



0-43 

 0.70 



0.90 



1 .00 



0-33 



0-43 

 0.52 

 0.77 

 0.92 

 1 .00 



0.13 

 o. 10 

 0.09 

 0.07 

 0.02 

 0.00 



Enzyme 0.05 per cent. Incubation 5 hours at 40 C. 



All of the vials contained sediment at the close of incubation. In 

 the unboiled w/1024 there was very little precipitate. Before incu- 

 bation the unboiled solutions remained water clear after the mixture of 

 enzyme and toxic salt until placed in the oven, so that the precipita- 

 tion was slow. 



'o This column gives the acidity of 4CC of the toxic salt solution of the concentra- 

 tion indicated by the corresponding figure in the column headed " m." 



