I0o8] 



POND—SOLUTION TENSION AND TOXICITY 



246 



TAHLK XVI 



Relativk toxicity with varyino concentrations of tiik enzyme 



Copper and zinc in contemporaneous test 



COPPER 



ZINC 



2048. 

 1024. 



512. 



256. 



128. 



0.08 

 0.06 

 0.06 

 0.04 

 0.00 



Enzyme o. 10 per cent. Iiu uhation 3 hours at 40 C. 



In Tables IX, XI, and XII, copper and zinc have the same point of 

 total inhibition, namely w/1024. In those tests the concentration of 

 the enzyme was 0.05 per cent. Here when the concentration of the 

 enzyme is doubled the relative toxicity is changed. The point of total 



TABLE XVII 



COPPER 



ZINC 



Enzyme o. 15 per cent. Incubation 5 hours at 40 C. 



inhibition for copper is w/256 and for zinc w/128. In Table XVII 

 where the concentration of the enzyme is still higher, the difference in 

 toxicity is more pronounced. 



In the work on ethyl butyrate, cadmium, cobalt, and zinc were 



