I9081 



POND— SOLUTION TENSION AND TOXICITY 



247 



found to become equitoxic with increasing concentration of the enzyme. 

 Here the relative toxicity of zinc as compared Avith that of copper 

 decreases with increasing concentration of the enzyme. In both ca^s 

 the tendency of zinc to lose in relative toxicity with increasing concen- 

 tration of the enzyme is apparent. 



TABLE XVIII: Mercury and silver in coiiternporaneous test 



MERCURY 



m 



Control 



8192 

 4096 

 2048 

 1024 



512 



Enzyme 



Increase 



. 20 



0.25 



0.05 



1 



0.25 



0.25 



0.00 



^-i2> 



^'i:^ 



0.00 



0-35 



0-35 



0.00 



0-53 



0-53 



0.00 



SILVER 



Enzyme o. 10 per cent. Incubation 5 hours at 40 C- 



Here the point of total inhibition for copper is the same as with the 

 lower concentration of the enzyme in the preceding table, but the zinc 



TABLE XIX 



MERCURY 



m 



Control 



8192 



4096 

 2048 

 1024 



o 

 o 

 o 

 o 

 o 



25 



25 



35 

 50 

 85 



Enzyme 



0.40 



0-35 

 0.40 



0-55 



0.88 



Increase 



0.15 



O.IO 



0.05 



0.05 

 0.03 



SILVER 



Enzyme 0.15 per cent. Incubation 5 hours at 40° C. 



fails to inhibit totally and shows plainly that it loses toxicity faster 

 than copper as the concentration of the enzyme increases. 



In Tables XIII and XI\' mercun' is four times more toxic than 



