From The Technology Quarterly, February, 1889. 
ON THE DETERMINATIONg'OF THE ORGANIC NITROGEi 
IN NATURAL WATERS/BY THE KJELDAHLAIETHOD. 
By THOMAS M. DROWN, M.D., and HENRY MARTIN, S.B. 
The justification for the almost universal practice of determining 
the organic nitrogen in waters in the form of albuminoid ammonia is to be 
found in the great simplicity of the Wanklyn process. The amount of 
nitrogen obtained in the form of ammonia by the action of alkaline per- 
manganate on nitrogenous organic matter in water bears no known 
relation to the total nitrogen present, and chemists report widely differ- 
ing results in consequence of differing practice. In the case of color- 
less waters, with small amount of organic matter, the differences are 
not usually great, but in most surface waters, with considerable organic 
matter in suspension and solution, the results often differ fifty or one 
hundred per cent. Some water analysts stop the distillation for albu- 
minoid ammonia when 150 c.c. have distilled over; others continue until 
250 c.c. are obtained, and again, others strive to get all the ammonia 
they can by the addition of more alkaline permanganate, or by replacing 
the water which has distilled over. 
There can be no doubt that the determination of the total organic 
nitrogen would be generally practised in place of the determination of 
the albuminoid ammonia, if there was available a short, easily executed, 
and accurate method for this purpose. 
As the result of a very large number of experiments with the Kjel- 
dahl nitrogen process, we think it may be safely said, that this method 
leaves little, if anything, to be desired in these respects. 
The modifications of the process, as usually practised, to adapt it to 
the determination of organic nitrogen in waters, are in the direction of 
its simplification. Thus, the amount of organic matter in water is 
ordinarily so very small that the use of solid potassium permanganate 
for the final and complete oxidation of the organic matter is probably 
never necessary. In most of the analyses which we have made, we have 
continued to use it as a matter of precaution, but in the comparative 
experiments, with and without its use, the results have not differed. 
The volumetric determination of the ammonia by titration with very 
dilute standard acid was found to be less accurate and less convenient 278 
Thomas. M. Drown and Henry Martin. 
[Feb. 
than the Nesslerization of the distillate, in the usual method employed 
in water analysis. Further, the same flask is used for both the diges- 
tion and the distillation. 
Professor W. R. Nichols experimented with the Kjeldahl process for 
the determination of the nitrogen in sewage with satisfactory results,* 
but the process has not yet, far as we know, been used in regular water 
analysis. 
The examination is conducted as follows : 500 c.c. of the water 
is poured into a round-bottom flask, of about 900 c.c. capacity, and 
boiled until 200 c.c. have been distilled off. The "free ammonia" 
which is thus expelled may, if desired, be determined by connecting 
the flask with a condenser. To the remaining water in the flask is 
added, after cooling, 10 c.c. of pure concentrated sulphuric acid.f 
After shaking, the flask is placed in an inclined1 position on wire gauze, 
on a ring-stand, or other convenient support, and boiled cautiously, in a 
good-drawing hood, until all the water is driven off and the concentrated 
sulphuric acid* is white or a very pale yellow. The flask is then removed 
from the flame, and a very little powdered potassium permanganate added 
until, on shaking, the liquid acquires a green color, showing that an 
excess of the permanganate has been added. Should the color be 
purple instead of green, it shows that the water has not all been driven 
off. After cooling, 200 c.c. of water free from ammonia are added, the 
neck of the flask being washed free from acid, and then 100 c.c. of so- 
dium hydrate | solution. The flask is immediately connected with the 
condenser, and then shaken to mix the contents. 
The distillation at the start is conducted rather slowly, and the first 
50 c.c. are condensed in very dilute hydrochloric acid.§ The contents 
of the flask may then be boiled more rapidly until 150 c.c. to 175 c.c. 
have altogether been collected. The total distillate is made up to 250 
c.c. with water free from ammonia, well mixed, and 50 c.c. taken for 
Nesslerization. No serious difficulty has been encountered from bump- 
ing when boiling the alkaline solution. The use of metallic zinc in the 
* Franklin Institute Journal, August, 1885. 
f It is necessary to have for this purpose sulphuric acid which is very nearly, if not quite, 
free from nitrogen in any form. Baker & Adamson, of Easton, Penn., make an acid for this 
purpose which contains only milligram of ammonia in 10 c.c. 
J The sodium hydrate solution is made by dissolving 200 grams of commercial caustic soda 
of good quality in 1.25 litres of distilled water, adding two grams of potassium permanganate 
and boiling down to somewhat less than a litre. When cold, the solution is made up to a litre. 
The addition of the permanganate is to oxidize any organic matter which may be present in the 
caustic soda. 
§ This acid should be free from ammonia: 1 c.c. of the acid is equivalent to 0.5 milligram 
of ammonia. .1889.] 
Determination of Organic Nitrogen in Natural Waters. 
279 
flask to facilitate the boiling is, of course, inadmissible, on account of 
the reduction of nitrates and nitrites, should they be present, to am- 
monia. 
Any efficient condensing arrangement may be used for the collection 
of the ammonia. We have used with great satisfaction the condenser 
devised by Prof. S. W. Johnson, of the Connecticut Agricultural Exper- 
iment Station, which is described in Bulletin No. 12, of the United 
States Department of Agriculture, Division of Chemistry. It consists 
of a copper tank, 20 inches high, 32 inches long, 3 inches across the 
bottom, widening to 6 inches at the top. The tank is provided with an 
adequate supply of running water, entering at the bottom, and accommo- 
dates 6 or 7 block-tin condensing-tubes three-eighth inch internal diam- 
eter, which enter the tank through holes in the front side near the top, 
above the level of the overflow, and pass down vertically through the tank 
and out through rubber stoppers tightly fitted into holes in the bottom. 
They project about 2 inches below the tank, and are connected by 
means of rubber tubes to straight glass calcium-chloride tubes, with a 
bulb at the upper end. These glass tubes dip into 250 c.c. flasks which 
receive the distillate. The distilling-flasks are connected with the tin 
condensing-tubes, by means of rubber stoppers which carry a bulbed- 
glass tube bent at right angles. This tube and its rubber stopper 
remain permanently connected with the tin tube. 
The flasks rest on iron rings, h.nd are heated with the free flame of a 
Bunsen burner. They should be carefully selected as to size and height, 
and the fixtures should be so arranged that all parts are interchange- 
able. There is then never any difficulty in putting the flasks promptly 
into place and connecting them with the condenser. 
It is a good plan to have flasks, partly filled with water free from am- 
monia, connected with the condensing-tubes when not in use. 
Before beginning a determination, the water in the flask is boiled 
until the distillate shows, on Nesslerization, that the apparatus is com- 
pletely free from ammonia. Into the flask which receives the distillate 
there is put 1 c.c. .of the dilute hydrochloric acid and 50 c.c. of water. 
The delivery tube dips into this liquid only during the collection of the 
first 50 c.c. of the distillate. The flask is then lowered so that the tube 
remains above the liquid for the remaining time of the distillation. 
In carrying out the operation, the most scrupulous care must be ob- 
served in preventing access of ammonia from any source. The acid 
solutions will absorb ammonia from the air of the laboratory or from the 
dust of the room if they are- allowed to remain uncovered for any length 
of time. This source of error has been found at times to be very large; 280 
Thomas M. Drown and Henry Martin. 
[Feb. 
quite enough to render a determination valueless. One experiment gave 
a gain of ammonia in twenty hours, by leaving the flask which contained 
the concentrated sulphuric acid uncovered, equivalent 0.5 c.c. of the 
standard ammonium chloride solution, and at another time the gain was 
3 c.c. 
The operation should, therefore, be carried out without interruption, 
and for every determination, or set of determinations, a blank analysis 
with ammonia-free water should be made for a correction for the am- 
monia in the reagents and that accidentally introduced in the process. 
We have not found that the presence of nitrates and nitrites in waters 
interferes with the accurate determination of the organic nitrogen. 
The error which has been found by Kjeldahl and Warrington * to be 
caused by nitrates in the determination of organic nitrogen seems to 
disappear under the conditions of great dilution which we have in 
natural waters. 
The following experiments bear on this point : - 
1500 c.c. standard ammonium chloride solution (= 15 milligrams NH3) 
and 10 c.c. of standard potassium nitrite solution (= 1 milligram N) 
were boiled with 10 c.c. of sulphuric acid, and the vapors condensed. 
This distillate contained only o. 15 milligram nitrogen as ammonia and 
nitrous acid. The residue in the flask was made alkaline and distilled, 
and the ammonia obtained was precisely the amount taken; namely, 
1500 c.c. The experiment was repeated, using a nitrate in place of the 
nitrite, and under the same conditions the 1500 c.c. of ammonia were 
recovered. 
When a smaller amount of ammonia was used, we still failed to ob- 
serve any loss. Thus when 10 c.c. standard ammonium chloride solution 
and 10 c.c. potassium nitrite solution (=0.1 milligram N) were treated 
as above, there was obtained ammonia equivalent to 10.5 c.c. Another 
experiment with the same quantities gave precisely 10 c.c. of ammonia 
regained. With potassium nitrate instead of nitrite, in the same pro- 
portions as in the foregoing experiment, 10.5 c.c. of ammonia were 
obtained. 
The attempt to collect all the nitrous-and nitric acids in the distillate 
was unsuccessful. The flask and condenser were connected by ground 
joints, so that the distillation could be continued after the sulphuric was 
concentrated. Owing, probably, to the shape of the flask, the acids 
were condensed, in part, in the neck of the flask, for after a second and 
a third addition of water and a renewal of the distillation more nitrous 
and nitric acids were obtained in the distillate. To see whether there 
* Chemical News, 52, p. 162. 1889.] 
Determination of Organic Nitrogen in Natural Waters. 
281 
was any loss of ammonia from ammonium sulphate in presence of sul- 
phurous acid from the action of sulphuric acid on carbonaceous matter, 
the following experiments were tried : io c.c. pf standard ammonium 
chloride solution were treated with io c.c. of sulphuric acid and a 
weighed amount of Swedish filter paper. Deducting for the nitrogen 
in the paper, determined in a blank analysis, 10.5 c.c. of ammonia were 
obtained. In a duplicate experiment the ammonia obtained was 10 c.c.,- 
precisely the amount taken. In still another experiment with 50 c.c. of 
standard ammonium chloride solution and filter paper, 51 c.c. were 
obtained. 
No attempt has been made to compare, as regard the results obtained, 
the above-described method of determining the organic nitrogen with 
the combustion method of Frankland and Armstrong. But the follow- 
ing experiments on very dilute solutions of organic substances of known 
composition may serve to confirm the accuracy of the method. 
One hundred milligrams of pure crystals of urea were dissolved in 
one litre of water free from ammonia. Ten cubic centimetres of this 
solution were added to 500 c.c. of water and the analysis conducted as 
above described. There was obtained 0.494 milligram, the theoretical 
amount being 0.466. In a duplicate experiment no solid potassium per- 
manganate was added to complete the oxidation, and the result was 0.486 
milligram. 
A solution of uric acid in dilute potassium hydrate was made of the 
same strength as the urea, and 10 c.c. taken for analysis. There was 
found 0.326 milligram of nitrogen; required, 0.333 milligram. In a 
duplicate experiment without the permanganate - precisely the same 
amount was obtained. 
A solution of naphthylamine, 100 milligrams to the litre, was dis- 
solved by the aid of dilute hydrochloric acid. An analysis of 10 c.c. 
gave 0.082 milligram nitrogen ; required, 0.097. Here, again, the result 
obtained by the omission of the permanganate agreed precisely with the 
determination in which the permanganate was used. 
The following series of experiments made on a sample of Cochituate 
water shows the very close agreement of results in the determination of 
organic nitrogen under varying conditions. From a large bottle of water 
freshly drawn from the tap, were taken five portions of 500 c.c. each. 
The first portion was treated by the usual method, already described. 
The second portion was treated like the first, except that the addition 
of solid permanganate was omitted. 
The third portion received 10 c.c. of standard potassium nitrate solu- 
tion, equivalent to o. 1 milligram of nitrogen. 282 
Thomas M. Drown and Henry Martin. 
[Feb. 
The fourth portion received 1 c.c. of potassium nitrite solution, equiv- 
alent to 0.01 milligram of nitrogen. 
The fifth portion contained ten times the amount of potassium nitrite 
as the fourth portion, or o. 1 milligram. 
The third, fourth, and fifth portions were treated in all respects like 
the first portion. 
The results, expressed in organic nitrogen, parts per 100,000, were : - 
No. 1. 
O.O354 
No. 2. 
0.0354 
No. 3. 
O.O354 
No. 4. 
O.O365 
No. 5. 
O.O365 
It may be of interest to give a few of the results obtained in the de- 
termination of the organic nitrogen by this method in natural waters in 
comparison with the results obtained as albuminoid ammonia. In the 
table following will be found the analyses of some Massachusetts waters 
during three successive months, June, July, and August, 1888. 
In the first column is a record of the color, based on a comparison 
with the Nesslerization of a known amount of ammonium chloride. 
Thus a color 1, means that the water possessed a color corresponding in 
depth and tint to 1 c.c. of standard ammonium chloride solution 
(=.00001 gr. NH3) when Nesslerized; a color of 2 is twice the depth 
of color, and o. 1 is one-tenth the color of 1. In the second column is 
the albuminoid ammonia obtained by the adding 40 c.c. of alkaline per- 
manganate to the water in the flask, after boiling off 150 c.c. for free 
ammonia, and then distilling over 250 c.c. In the third column is the 
organic nitrogen determined by the Kjeldahl process, converted into 
ammonia to make the figures comparable with the second column. All 
the determinations were made on the waters filtered through paper in 
the laboratory. 1889.] 
Determination of Organic Nitrogen in Natural Waters. 
283 
Comparison of Albuminoid Ammonia and Organic Nitrogen 
in Natural Waters. 
I. Surface Waters. 
Water. 
. Albuminoid 
CoIor- Ammonia. 
Organic 
Nitrogen 
calculated as 
Ammonia. 
Arlington, Reservoir - 
June . 
. .8 
.0256 
.0560 
July • 
• -3 
•0274 
.0560 
Boston Supply, Basin 4 
- 
June . 
. 1.0 
.0226 
.0470 
July • 
• -7 
•0234 
.O4OO 
August 
• -9 
•0254 
.0460 
Boston Supply, Basin 2 
- 
June . 
. 1.4 
•035° 
•0590 
July • 
• i-3 
.0294 
•°45° 
August 
• .85 
•0234 
.0440 
Boston Supply, Basin 3 
- 
June . 
. 1.9 
•0392 
.0790 
July • 
• r-7 
•0336 
.0540 
August 
. .8 
.0278 
•0590 
Boston Supply, Lake Cochituate 
June . 
• -35 
.0176 
.0420 
July • 
. .10 
.0192 
•0390 
August 
. .10 
.0196 
.0420 
Boston Supply, Mystic Lake - 
June . 
. .20 
.0252 
.0590 
July • 
. .10 
.0244 
.0560 
August 
• -15 
.0212 
.0420 
Bridge water, Taunton River - 
June . 
■ 2.3 
.0248 
•0520 
July •• 
. 1.0 
.0210 
.0440 
August 
• -7 
.0212 
•0390 
Brockton, Reservoir - 
June . 
• -9 
.0234 
•0570 
July • • 
• -9 
.0260 
.0490 
August 
• -7 
•0310 
.0610 
Brookline, Charles River - 
June . 
. 1.20 
.0320 
■0520 
July • 
. .60 
.0216 
.0470 
August 
• -45 
.0208 
.0380 
Cambridge, 
Fresh Pond 
June . 
. .20 
.0162 
•037° 
July • 
• -IS 
.0170 
•0390 
August 
. .0 
.0172 
•0390 
,,7 . , Albuminoid 
Water. Color. Aramonia. 
Clinton, Nashua River - 
Organic 
Nitrogen 
calculated as 
Ammonia. 
June . . 
.1 
.0072 
.0230 
July • • 
.2 
.0144 
.0360 
August . 
.2 
.0124 
.0320 
Fitchburg, Reservoir- 
June . . 
.1 
.0124 
•0250 
July • • 
.1 ' 
.0158 
•0340 
August . 
.1 
.0146 
.O24O 
Great Barrington, Housatonic River - 
June . . 
.1 
.0122 
.O32O 
July • • 
.1 
.0120 
.0270 
August . 
•O 
•oi34 
.0320 
Nashua, Merrimac River - 
June . . 
•4 
.0120 
.0320 
July • • 
.2 
•0132 
.0290 
August . 
.2 
.0106 
.0290 
Lowell, Merrimac River - 
June . 
•3° 
.0142 
.0420 
July • • 
.IO 
.0148 
.0280 
August . 
•25 
•oi34 
.0320 
Haverhill, Merrimac River - 
June . . 
.40 
.0164 
.O49O 
July • • 
.20 
.0170 
.0420 
August . 
.20 
■0163 
.0348 
Lake Winnepesaukee 
- 
June . . 
.O 
.0090 
.0230 
July • • 
•O 
.0082 
.0190 
August . 
•O 
.0080 
.0200 
Hyde Park, 
Neponset River - 
June . . 
.6 
.0286 
.0520 
July ■ • 
.8 
•0432 
.IIOO 
Lynn, Birch Pond - 
June . . 
•45 
•0194 
.0420 
July • • 
•35 
.0216 
.O4IO 
August . 
•25 
•0174 
.O4IO 
Malden, Spot Pond - 
June . . 
•3 
.0216 
.O44O 
July • • 
.2 
.0198 
.0390 
August . 
.2 
.0216 
•0390 284 
Thomas M. Drown and Henry Martin. 
[Feb. 
Water. 
Albuminoid 
Color- Ammonia. 
Organic 
Nitrogen 
calculated as 
Ammonia. 
Montague, Connecticut River - 
June . 
• -i5 
.0120 
.0220 
July • 
. .20 
,OIl8 
.0250 
Springfield, Connecticut River - 
June . 
• -4 
•0132 
.0390 
July • 
• -15 
.OI46 
.0320 
August 
• -15 
.OI7O 
.0380 
New Bedford, Acushnet River - 
June . 
• 2.3 
.0296 
•O54O 
July • 
. 1.8 
.0278 
•0540 
Northboro, Assabet River - 
June . 
• -7 
.OI92 
.0490 
July • 
• -4 
.0216 
.0380 
August 
• -4 
•0174 
.O4IO 
Salem, Wenham Lake 
- 
June . 
. .10 
■0132 
.0320 
July • 
• -05 
•OIl8 
.0290 
August 
. .00 
■0130 
.0260 
Springfield, 
Ludlow Reservoir - 
June . 
.0222 
.0460 
I .20 
.0214 
.O44O 
July • 
. .IO 
.0220 
.0420 
Water. 
Color. 
Albuminoid 
Ammonia. 
Organic 
Nitrogen 
calculated as 
Ammonia. 
August 
J .05 
1.10 
.OI98 
.0206 
•0390 
•037° 
Wayland, Reservoir- 
June . 
• i-5 
.0272 
•0590 
■ July • 
• -9 
■0364 
.0660 
August 
. .4 
.0244 
•0540 
Whitman, Hobart's Pond - 
June . 
• !-7 
.0538 
.0990 
July . 
• i-5 
.0426 
.0990 
August 
• -9 
•0342 
.0740 
Wilmingto: 
n, Shawsheen River - 
June . 
. .8 
.0242 
.0640 
July • 
• 15 
.OII4 
•037° 
August 
. 1.00 
■0316 
•0570 
Woburn, Horn Pond 
' 
June . 
• -35 
.0290 
•0570 
July • 
• .25 
■0324 
•0590 
August 
. .10 
.0240 
.0440 
Worcester, Blackstone River - 
June . 
. - 
•0350 
•135° 
July • 
. - 
.O44O 
•1550 
August 
. - 
.0830 
.3800 
II. Ground Waters. 
( Without Color.') 
Water. 
Albuminoid 
Ammonia. 
Organic 
Nitrogen 
as Ammonia. 
Brookline, Filter Gallery - 
June . . . . 
. .0046 
.OI9O 
July . . . . 
. .0046 
.0220 
August . . . 
. . .OO42 
.0170 
Newton, Filter Gallery - 
June . . . . 
, . .0044 
.0190 
July . . . . 
, . .0072 
.0160 
August . . . 
. .0052 
•OIOO 
Revere, Wells - 
June . . . . 
. .0018 
•OO34 
July . . . , 
. . .0034 
.0070 
August . . . 
, . .0018 
•OIOO 
Water. 
Albuminoid 
Ammonia. 
Organic 
Nitrogen 
as Ammonia. 
Revere, Reservoir - 
June .... 
• -0034 
•0130 
July .... 
. .0046 
.0150 
August . . . 
. .0060 
.0190 
Waltham, Filter Gallery - 
June .... 
. .0030 
.0170 
July .... 
. .0050 
.0160 
August . . . 
. .0056 
.0150 
Waltham, Reservoir 
June .... 
. .0042 
.0230 
July .... 
. .0042 
.0180 
August . . . 
. .0060 
.0160 
It will be noted that the organic nitrogen in the surface waters is 
in general about double the albuminoid ammonia. The average of all 
the analyses of the waters given above is 0.0214 for the albuminoid 1889.] 
Determination of Organic Nitrogen in Natural Waters. 
285 
ammonia, and 0.0476 for the organic nitrogen. In the ground waters 
the relation of the albuminoid ammonia to the organic nitrogen is still 
less. Too much importance must not, however, be given to this relation 
in the case of the ground waters, for it is probable that the figures given 
for the organic nitrogen are all a little high, owing to the fact that 
all of the sources of error were not fully known when most of the 
analyses were made. The proportional excess in case of the surface 
waters is believed to be insignificant, but with the smaller content of 
nitrogen in the ground waters the error is perhaps proportionately large. 
Massachusetts Institute of Technology, 
February, 1889.