245 



BOTANICAL GAZETTE 



[april 



but with silver total inhibition may occur in the absence of any precipi- 

 tation. The following test reinforces the result of this one. 



In Table XIV the reagent acidity is omitted, as it may easily be seen 

 in Table XIII and most of the values are zero anyhow. The relative 

 toxicity is the same, athough the exact point of total inhibition is dif- 

 ferent. In the case of silver there was no deposit in any of the unboiled 

 solutions, while with mercury there was deposit in w/16384 and in 

 higher concentrations, while greater dilutions were free from deposit. 

 To determine at what point precipitation first appears in the case of 

 silver the following test was made. 



TABLE XV: Silver in solitary test 



SILVER 



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



The lowest concentration of the reagent to show any natural acidity 

 was the w/1024, and greater dilutions were neutral to the indicator 

 used. The only vials of the unboiled series to show a deposit after in- 

 cubation were the w/1024. 



A comparison of the results of this work on the acetate with those 

 obtained in the work on ethyl butyrate shows that the same general 

 relation holds for both. The metals fall into groups according to 

 toxicity. The groups are not so clearly separated in the case of the 

 acetate, but still sufficiently distinct to confirm the conclusion drawn 

 in regard to the lipolysis of ethyl butyrate. 



In the work on the ethyl butyrate it was found that the relative tox- 

 icity changes according to the concentration of the enzyme — a result 

 not in accord with the conclusion of Caldwell (/. c.) . The following 

 tests show that concentration of the enzyme is a factor in relative tox- 

 icity, and adds emphasis to my result with ethyl butyrate. 



