[Reprinted from the Journal of the Franklin Institute, August, 1885.] 
CONTRIBUTIONS to our KNOWLEDGE of SEWAGE. 
By Wm. Ripley Nichols and C. R. Allen. 
In the year 1872, one of us had occasion to report* the results of 
the chemical examination of a considerable number of samples of the 
sewage of Boston and of Worcester, Mass. The examinations then 
made included the determination of the nitrogen existing as ammonia 
or in the form of ammoniacal salts (tabulated as free ammonia), and 
of the nitrogen which was given off as •ammonia by treatment with 
an alkaline solution of permanganate of potash, according to the well- 
known method of Wanklyn. As- indicating the total amount of 
organic nitrogen, this last determination—that of the so-called “albu- 
minoid ammonia”—was felt at the time to be inadequate, but under 
the then existing circumstances it was the best that could be done. 
When Kjeldahl’s process for the determination of the total nitrogen 
in organic substances was published a few years ago,f it suggested 
itself at once that the.method might possibly be conveniently applied 
to the analysis of sewage. Circumstances have prevented, until 
recently, the carrying out of this idea; meanwhile, the process has 
found extensive application, especially in agricultural laboratories, and 
has been used in the analysis of certain kinds of fertilizers. It is pos- 
sible that it may have elsewhere been applied to the examination of 
sewage; if so, we have failed to meet with notice of such application, 
which we find to be quite practicable and to give satisfactory results. 
In order to familarize ourselves with the process and, at the same 
time, to become satisfied of its substantial accuracy, determinations of 
* Fourth Annual Report of the State Board of Health of Massachusetts. 
Boston, 1873. Pp. 65-81. 
f Fresenius Zeitschrift, xxii (1883), p. 366; Chemical News, xlviii (1883), 
p. 101. 2 
the total nitrogen were made in sulph-urea, in dried and powdered 
horse dung, and in dried and powdered human excrement, the amount 
of nitrogen being checked either by theory or by an absolute determi- 
nation according to Dumas’ method. The results were as follows: 
I. 
Kjeldahl’s method. 
II. 
Dumas’ method. 
III. 
Theory. 
Sulph-urea 
36-89 per cent. 
3-16 
3-12 
0-20 “ 
3-28 
36-84 
“ 2 
6-08 
In order to satisfy ourselves as to the constancy of the results 
obtained in a number of determinations made on the same sample of 
actual sewage, a sample was procured and analyzed with the following 
results: 
Organic Nitrogen-Expressed as Parts in 100,000. 
Kjeldahl 
(after deducting nitrogen as free ammonia). 
Dumas. 
375 
3-66 
3-50 
3-75 
3-70 
3-75 
3-75 
3-80 
It thus appears that the process gives uniform results, and that these 
results are sufficiently accurate for the purpose. It has the advantage 
of requiring only the ordinary apparatus used in water analysis, as 
generally conducted in this country, and of avoiding a dry combustion, 
which, in the simplest form, is more or less troublesome, especially 
where a liquid has to be evaporated, and the solid residue transferred 
from the evaporating dish. 
There is little doubt that the coming decade will see in this country 
a considerable application of the method of disposing of sewage by 
irrigation, and it seems to us that Kjeldahl’s process will afford a ready 3 
means of determining the amount of that important constituent—the 
combined nitrogen. The process, as we have used it with sewage is as 
follows: 
From 25 to 50 cubic centimeters of sewage are introduced into a 
small flask, preferably flat bottomed, made acid with sulphuric acid 
and evaporated to dryness on a water-bath. This is best and most 
rapidly accomplished by drawing through the flask a somewhat rapid 
current of air which has been freed from moisture and ammonia by 
bubbling through strong sulphuric acid. We have satisfied ourselves 
that the loss of “ free ammonia ” by this treatment is inappreciable so 
that the residue contains the total combined nitrogen* of the sewage. 
This residue is treated in the flask with 5 cubic centimeters of fuming 
sulphuric acid which is run in from a glass-stoppered burette. The 
flask is placed on a piece of wire-gauze over a small gas-flame and 
heated until a light yellowish-brown liquid is obtained. With sewage 
this result is sometimes reached in half an hour; usually from one to 
two hours are required. Permanganate of potash is then added to 
complete the oxidation, a few crystals being sufficient.! 
The contents of the flask are then washed into the distilling apparatus 
with about 500 cc. of pure distilled water, enough caustic potash is 
added to give an alkaline reaction, and the nitrogen, which is now all 
in the form of ammonia, is distilled off in the usual way. The dis- 
tillate is made up to 250 cc. and aliquot portions are nesslerized as in 
water analysis. As the sulphuric acid usually contains a trace of 
nitrogenous compounds, a blank experiment determines a slight correc- 
tion to be applied. 
The process as just given may be modified by evaporating the 
sewage without first acidulating with sulphuric acid. The evaporated 
water may be condensed and the free ammonia determined therein and 
an approximate determination of the total solids may be made by using 
a tared flask. We prefer, however, to proceed as indicated above and 
to make a separate determination of free ammonia, with which may be 
coupled, if desired, a determination of the so-called albuminoid 
ammonia. 
* The nitrogen which exists in the sewage as nitrites and nitrates is too 
small to be of practical importance although there is usually a trace, 
f For fuller details, see Kjeldahl’s original paper, referred to above. 4 
BOSTON SEWAGE. 
Since the examinations of sewage made in 1872, the Boston system 
of sewerage has undergone an entire change. Instead of being dis- 
charged from short sewers emptying at intervals along the water-front, 
the sewage is now collected into one encircling sewer, carried by 
means of a tunnel to Moon Island and allowed to flow into the outer 
harbor on an ebb tide. 
We have examined a number of samples taken from the pumping 
station at City Point where the sewage is lifted in order that it may 
flow through the tunnel to Moon Island. The sewage was received as 
a rule in a fresh condition; the heavier suspended particles were 
allowed to subside ami no attempt was made to determine their amount. 
In fact, the determination of suspended matters in small samples is of 
little value and a more practical idea of their amount could be obtained 
on a large scale by estimating the amount deposited in the settling- 
tanks. The following: table contains the results of the examination of 
various samples of sewage from the pumping station. It will be noticed 
that the samples taken at different times vary very much from each 
other. The large amount of totah solids and chlorine are said to be 
due to the fact that a considerable quantity of sea-water is used in 
certain manufactories for cooling purposes and to the infiltration of 
salt water into the sewers which are below the tide level. 
NITROGEN AS UREA. 
The rapidity with which urea is converted into carbonate of ammonia 
and water in the presence of the urea ferment which is probably 
always present in sewage, would prevent its existence in stale sewage, 
but as the Boston sewage reaches the point from which our samples 
were taken in a fresh condition, we might expect to discover some of 
this substance still unchanged. 
The evidence that urea was present in several samples which were 
tested is as follows: Two portions of 50 cc. each were boiled in small 
flasks to expel the free ammonia and to kill any of the ferment present, 
and the necks of the flasks then stopped with cotton wool. When the 
contents had become cool one of the flasks was infected by dipping a 
glass rod first into a fermenting solution of urea, or into stale sewage and 
then into the boiled sample. The two samples were allowed to 
stand side by side for several days, and then examined for free 5 
Number. 
Date of Collection. 
Ammonia 
Albumin- 
oid 
Ammonia 
Total Ni 
reckor 
Nitrogen. 
trogen, 
led as 
Ammonia 
Total 
Solids. 
Chlorine. 
Chlorine 
reckoned 
as com- 
mon salt. 
Phosphor- 
ic Acid. 
(P0O5.) 
1 
1885. 
May 12, 7.30 P. M 
2-80 
0-27 
2-80 
3-40 
592 
275 
453 
0-480 
2 
13, 8.20 A. M 
3 18 
0-44 
3-46 
4-20 
548 
258 
425 
0-096 
3 
13, 7.20 P.M 
3-42 
1-15 
5-76 
7-00 
254 
82 
135 
0-672 
4 
14, 7.20 A. M 
1-32 
0-35 
1-81 
2-20 
570 
247 
407 
0-704 
5* 
15, 1.00 A. M 
1-29 
0-87 
4-63 
5-62 
482 
133 
219 
1-313 
6* 
15, 8.15 A. M 
1*59 
0-25 
6-00 
7-30 
416 
194 
320 
0-512 
7 
15, 4.00 P. M 
3-08 
0-55 
3.76 
4-57 
358 
145 
239 
0 192 
8 
16, 7.30 A. M 
0-95 
0-55 
2-14 
2-60 
630 
311 
513 
0-288 
9 
17, 4.25 P. M 
5-68 
5’96 
14 -53 
17-65 
551 
215 
354 
7-035 
10 
18, 8.00 A. M 
6-23 
5-84 
13-82 
16-78 
528 
? 
? 
6-490 
11 
24, 7.50 P. M 
11-94 
3*32 
17-15 
20-82 
178 
59 
97 
3-325 
12 
23,12.40 A. M 
? 
2-62 
4-32 
5-30 
378 
178 
293 
0-992 
13 
26, 12 hour day average! .... 
5-71 
4-22 
11-32 
13-75 
460 
177 
292 
4-893 
14 
27, 12 “ “ “ t 
5-71 
3-31 
9-55 
11-60 
610 
288 
475 
6-188 
15 
28-29, 24 “ average! 
3-13 
5-49 
9-82 
11-93 
588 
240 
396 
4-702 
1872. 
2*72 
0 73 
19 
31 
1-691 
“ “ 4 night “ 
1*33 
0-23 
17 
4*5 
7-4 
* Samples 5 and 6 contained a good deal of storm water. f Samples taken every four hours. X Samples taken every two hours, 
j!Samples from sewers near the water front, which evidently contained much sea-water, were not included in these averages. 
1 Average of 19 samples. 
Examination of Boston Sewage. 
[Results expressed in parts in 100,000.] 6 
ammonia is a similar fashion. In one case the flask which had not 
been impregnated was free from ammonia, generally, however, a small 
amount of ammonia had developed itself,* in all cases the impregnated 
flasks showed a much greater amount of ammonia than was contained 
in the companion flasks. This certainly points to the presence of 
urea or some similar fermentable nitrogenous compound in the sewage 
as it reaches City Point. 
In conclusion we desire to acknowledge our indebtedness to the 
Department of Improved Sewage for facilities in collecting samples, 
especially to Mr. Barnes, at Chester Park, and to Mr. M. H. Holmes, 
at the pumping station.