copper- zinc couple method in estimating nitrates. 443 
In each series of experiments the bottles were exactly the same 
size and each bottle contained 100 c.c. of the solutions. In the 
first series A, one solution contained no couple, whilst the other 
bottle contained a copper-zinc couple. In the second series of 
experiments B, potassium nitrate of known volume and strength 
was added to the couple and solutions. The stoppers of the 
three bottles were always firmly inserted. 
The dissolved organic substances were soluble peptones, blood 
serum, soluble albumin, containing neither nitrites nor nitrates. 
And a sewage was used in the later experiments also free from the 
latter substances, determined previously by other methods. In each 
series of experiments different samples of the various substances 
were always used. 
A. In the first series, two experiments of each solution were 
conducted, one solution containing a couple and the other without, 
the latter being called the blank experiment. The first column of 
the following table gives the name of the substance and the 
strength of its solution ; the second column indicates the amount 
of ammonia produced in the blank experiment ; the third column 
that produced when the couple was present; and the fourth column 
the excess of the latter over the former. 
. 
Name of substance, and 
strength of solution 
Amount of NH.. 
produced in 
100 c.c. in blank 
experiment 
Amount of NH 3 
produced in 
100 c.c. when 
couple present 
Excess of NH.j 
produced by 
couple, in parts 
per 100,000 
Peptone 
0 002 gm. per litre 
0-0000071 gm. 
0-0000086 gm. 
0-0015 gm. 
0-020 „ 
0000040 „ 
0-000051 „ 
0-0110 „ 
0 020 „ 
0-000013 „ 
0-000024 „ 
0-0110 „ 
0-200 „ 
0-00060 
0-00017 
The 0-2 gm. per litre putrified during the blank experiment, so that no real 
comparison could be made. 
Blood serum 
l - 0°/ solution ... 
0-000011 gm. 
very large excess 
0-25 °/ o „ 
0-000014 „ 
0-00006 gm. 
0 - 0580 gm. i 
0-05 •/. „ 
0-0000071 „ 
0-000025 „ 
0 0179 „ 
It is clear from the above numbers that ammonia is produced 
by the couple in larger amounts than when the solutions are 
incubated without the couple. The gases produced by the action 
of the couple assist the breakdown of the complex nitrogenous 
compounds in solution, and ammonia is one of the final products 
of the degradation. 
