Extracted from the American Journal of the Medical Sciences for July, 1881. 
QUANTITATIVE DETERMINATION OF UREA 
BY ALKALINE HYPOCHLORITES AND 
HYPOBROMITES 
J?Y 
THEO. G. WORMLEY, M. D., 
PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF PENNSYLVANIA. [Extracted from tlie American Journal of the Medical Sciences for July, 1881.] 
QUANTITATIVE DETERMINATION OF DREA BY ALKALINE 
HYPOCHLORITES AND HTPOBROMITES. 
By THEO. G. WORMLEY, M.D., 
PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OP PENNSYLVANIA. 
The determination of the amount of urea present in the urine by the 
volume of nitrogen evolved under its decomposition by sodium hypochlo- 
rite, was first proposed by Davy {Philosoph. Mag., 1854, p. 385). Ac- 
cording to his observations, the quantity of nitrogen evolved corresponded 
very closely to the calculated amount present in the urea. But according 
to the observations of M. Leconte {Ghem. Gaz., 1858, 433), with a.differ- 
ent form of apparatus, under the action of this reagent only about 92 per 
cent, of the nitrogen is evolved. 
Messrs. Russell and West proposed to substitute for the hypochlorite an 
alkaline solution of sodium hypobromite, and advised a special form of 
apparatus for the application of the test {Jour. Ghem. Soc., Aug. 1874, 
and jlm. Jour, ]\Jed. Sci., April 1870, p. 531). These observers however 
obtained only about 94 per cent, of the total nitrogen. 
Under the action of either of these reagents, as is well known, the urea 
is resolved into carbon dinoxide, water, and free nitrogen, thus: 
CN2H,0 -f- SNaBrO = C02 -f 2H20 +N2 + 3Naßr. 
Theoretically, therefore, the whole of the nitrogen should be evolved, but 
it is generally admitted that in practice this is not the case. According 
to at least one observer, this loss is due to a portion of the nitrogen being 
retained as a cyanate; whilst according to another it is retained as a 
nitrate. 
To remedy this defect, M. Mehu advised to mix either glucose or cane- 
sugar with the urine before adding the hypobromite, when the whole of 
the nitrogen would be set free ( Compt. rend., 1879, 175). But, according 
to M. Esbach {lbid., 417), and also to M. Jay {Bull Soc. Ghim., 1880° 
105), a solution of glucose alone evolves some gas under the action of the 
reagent. Again, M. Fauconnier obtained in the presence of glucose, from 
a given quantity of urea, the theoretical amount of nitrogen ; whilst in the 
presence of cane-sugar he obtained only 94 per cent, of the total nitrogen 
(.Ihid,, 102). 
According to my own experiments, when a solution either of cane-suoar 
O or of glucose is mixed, at least in certain proportions, with the hypobro- 
mite reagent, without the presence of urea, the temperature of the mixture 
increases and its yellow colour is gradually discharged, but no gas is evolved. 
When 1 gramme of cane-sugar in 5 c.c. water was added to 10 c.c. of the 
reagent (prepared as stated hereafter) at 21.1° C. (70° F.), the mixture at 
the end of twenty-five minutes acquired a temperature of 30° C. (86° F.), 
after which the temperature slowly fell. 
In a similar experiment with glucose, the temperature increased from 
21° C. (69.8° F.) to 35.5° C. (96°. F.) in ten minutes, which was the 
maximum reached. It was also observed that the presence of large excess 
of glucose entirely prevented the decomposition of urea by the hypobromite 
reagent. 
For the purpose of examining the accuracy of this test for urea, without 
the presence of cane-sugar or glucose, the form of apparatus, at least in prin- 
cipal, advised by R. Apjohn (Ghent. News, Jan. 1875, 37), was employed. 
This consists of a wide-mouthed bottle in which is placed the reagent, 
and also a small test-tube, for containing the urea solution, of about 10 c. c. 
capacity and of such length as to stand inclined in the bottle. The mouth 
of the bottle is closed with a rubber stopper carrying a glass tube, by which 
it is connected by rubber tubing to a graduated burette divided into c. c. 
and suspended in a long cylinder of water from an adjustable arm. 
The urea solution is placed in the small tube within the charged bottle, 
the apparatus closed, and when there is no longer any change in the 
height of the column of liquid within the graduated tube, this is so adjusted 
that the surface of the contained liquid exactly coincides with that in the 
cylinder. This point, the temperature, and in exact experiments the 
barometric pressure being noted, the urea solution is mixed with the re- 
agent by inclining the bottle and gently shaking the mixture. As the 
evolved nitrogen collects in the graduated tube, the latter is gradually 
raised to relieve the contained gas from the increased pressure. When 
the evolution of gas has entirely ceased and there is no longer any change 
in the volume of gas, the tube is finally adjusted and the exact volume noted. 
The reagent employed was prepared, as first advised by Messrs. Russell 
and West, by dissolving 100 grains caustic soda in 250 c.c. water, and 
adding to the cooled mixture 25 c. c. bromine. In applying the reagent 
it was diluted with a volume and a half of pure water. 
With this arrangement a series of experiments was performed employ- 
ing 1 c. c. of a standard solution of pure urea varying in strength from one 
to six per cent., variously diluted, and added to varying quantities of the 
reagent. These experiments gave different results, in some only about 90 
per cent., and even less, of the nitrogen being evolved, while in others a 
larger proportion was obtained, and in still others the whole of the nitro- 
gen was set free. It was finally observed that under certain conditions 
the whole of the nitrogen is uniformly eliminated. These conditions are:— 1. The reagent should be freshly prepared. 
2. The urea solution should be wholly added to the reagent, none of 
the latter being allowed to mix with the urea solution in the 
containing tube. 
3. The amount of urea operated upon should not exceed one part to 
about twelve hundred parts of the diluted reagent. 
Moreover, the diluted urea solution should be added in small portions 
at a time to the reagent, thoroughly mixed, and the effervescence allowed 
to cease before any further addition of urea. So, also, it would appear, at 
least when comparatively large quantities of urea are present, that the 
surrounding temperature should not be less than about 20° C. (68° F.). 
In the practical application of the test, if a two per cent, solution of 
urea is under examination, 1 c. c. of the solution, diluted with from 5 to 
10 c. c. water, is placed in the containing tube, and the mixing bottle 
charged with 10 c. c. of the reagent diluted with 15 c. c. water; whereas, 
for 1 c. c. of a four per cent, solution of urea, similarly diluted, not less 
than about 50 c. c. of the diluted reagent should be employed. 
In a final series of experiments, in which the above conditions were 
observed, the temperature being noted to TL degree, and the results re- 
duced to the standard temperature (0° C.) and barometric pressure (760 
mm.)? the following average results were obtained:— 
Urea employed. Nitrogen evolved = 
10 milligrammes, 9.98 mgrm. urea. 
20 “ 20.07 “ 
SO “ 29.95 “ 
40 “ 39.88 “ 
In these experiments it was assumed that 1 gramme of urea contains 
372 c.c. nitrogen, measured at 0° C. and 760 mm. barometric pressure; 
or, that each c. c. of nitrogen evolved, measured under the conditions 
stated, represented .002688 gramme urea. 
During these investigations it was observed, in cases in which the whole 
of the nitrogen was not evolved, that so long as the conditions remained 
the same, the relative proportion of the nitrogen eliminated was pretty 
uniform. Hence, if the volume of nitrogen evolved from a known quan- 
tity of urea under certain conditions, or by a given form of apparatus, be 
determined, the result may be taken as the basis for the determination of 
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