W. MANSFIELD CLARK 



195 



may be described as — .025 volts. If the culture maintains its pH value at 7.2 and then 

 reduces indigo disulphonate to the extent of 85 per cent, the tables show that the re- 



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duction intensity may be described as —.157 volts. But if at 85 per cent reduction of 

 indigo disulphonate pH should have changed to 6.6, the potential would be —.081. 



