of sewage (1) in alkaline solutions, (2) in distilled water. 359 
and with sea-water in so far as there is a slow and gradual 
decrease in the total ammonias : but that with regard to the 
production of nitrates there is some difference in that both in the 
alkaline and non-alkaline solutions there are definite, although 
very small, quantities of nitrates produced, which was not the 
case when the sewage was incubated with salt solutions and with 
sea- water, although the amount of nitrates in the alkaline solutions 
is considerably smaller than in the non-alkaline solutions. 
The preceding tables (p. 358) give the results of a third series 
of experiments where sewage was incubated with an alkaline 
solution and with distilled water. 
The incubations were continued for 37 and 49 days, and the 
nitrates and nitrites alone determined in these two later incubations. 
The general results are similar to those of experiments I. and 
II., namely, (1) there were smaller quantities of nitrates in the 
alkaline than in the non-alkaline solutions, and (2) a progressive 
diminution in the total ammonias. 
The following tables give the results of an earlier analysis 
made by Purvis and Coleman, when a sewage was incubated 
with distilled water, similar to the before-mentioned non-alkaline 
solutions. 
Time 
Free NH 3 
Albumin- 
oid nh 3 
Total NH 3 
Nitrates 
Nitrites 
Commencement . . . 
0-32 
0-12 
0-44 
absent 
absent 
1 day 
0-48 
0-16 
0-64 
trace 
2 days 
0-59 
0-20 
0-79 
0-025 
8 weeks 
0-60 
0-10 
0-70 
0-120 
5) 
The results again show a development of nitrates and a slow 
decrease in the total ammonia figures, and they are comparable 
with the incubations in the above non-alkaline solutions. 
General Conclusions. 
On comparing these results, it is evident that the action of the 
salts in sea-water seriously interfered with the decomposition of 
any sewage poured into it. There was only a slow production of 
the two ammonias, although there was a progressive decline in the 
amount ; and the nitrates were so small in amount that they must 
have been less than 0'005 parts per 100,000. And the present 
experiments prove that when sewage was incubated in slightly 
alkaline solutions there were definite amounts of nitrates pro- 
duced : whilst there was a greater production when the incubations 
24—2 
