445 
copper-zinc couple method in estimating nitrates. 
that such ammonia is produced by the reduction of the nitrates, 
for there were no nitrates present. 
And, secondly, there is the effect of the couple when acting in 
the presence of potassium nitrate; and here the results are variable. 
In some instances the amount of ammonia produced is greater than 
would be produced by the reduction of the added nitrate, and in 
others it is less. In the former case the numbers indicate that the 
dissolved nitrogenous compounds have also been partly degraded ; 
whilst in the latter case the meaning is not so clear, and it should 
be mentioned that in several incubations we noticed the presence 
of nitrites at the end of the experiments, indicating that complete 
reduction of the nitrates had not been accomplished. 
To explain these results, it is suggested that it is not only the 
hydrogen liberated by the couple which influences the decomposi- 
tion, but also partly the oxygen produced by the electrolytic action. 
Both elements would be in the nascent condition, and temperature 
and time would be conditioning influences of the total effect. 
Under these influences the degradation of the dissolved compounds 
would be greatly facilitated, with the production of free ammonia 
as one of the final products. If it were the result of an analysis of 
a sewage or of any solution containing considerable quantities of 
nitrogenous substances, it would be erroneously attributed to the 
reduction of nitrates. 
With regard to the numbers obtained from the incubations in 
the presence of potassium nitrate, it may be that the effect of the 
couple is not always to isolate the nitrate or the nitrogenous sub- 
stances and to complete the reduction of one before acting upon 
the other. It may be that the conditions of equilibrium of the 
organic compounds determine the direction of the reduction. 
In some instances the equilibrium may be such as to be easily 
affected by the nascent gases produced by the couple ; whilst in 
others the effect is to act simultaneously on the nitrates and the 
organic substances so that both are only partially affected ; and, 
within the time limits of the experiment, the complete reduction 
of the added nitrate would not be accomplished. Further, the 
increased ammonia, above that equivalent to the added nitrate, may 
be due partly to the oxidising influence of the nitrate itself ; and 
this influence may be strengthened by the potash produced as the 
electrolytic action proceeds. So that the final result is caused 
by several influences ; and the ammonia produced by the reduction 
does not represent that which is obtained from the nitrate alone. 
