680 
UREA IN THE URINARY SECRETIONS. 
furnished in one experiment, 0*3001, and in another, 0*3069 
parts of a cubic inch of gas, at the same temperature and 
pressure, which shows that the calculated quantity of nitrogen 
differs from the amount of nitrogen gas obtained by only a 
few thousandths of a part of a cubic inch. I may observe, 
that I was obliged to operate on such small quantities of 
urea, on account of the graduated tube I had at the time 
being only of one cubic inch capacity. Seeing, then, that 
the quantity of gas evolved agrees so very closely with the 
calculated amount of nitrogen present in a certain quantity 
of urea, I take the calculated amount as being the more 
correct, and knowing the relation that exists between a cer- 
tain quantity of urea and nitrogen, I can, from the quantity 
of gas evolved in any case, easily calculate the amount of urea 
present, by the simple process of rule of three. 
Thus, the fifth part of a grain, or 0*2 of a grain of urea 
gives, by calculation, 0.3098 parts of a cubic inch of gas. 
Then, 0*3098 : the volume of gas found : : 0*2 : to the re- 
quired quantity of urea, or, multiplying the first and third 
terms by five, we have 1*549 cubic inch of gas representing 
T grain of urea, which is a simpler proportion. Using this 
data, I made several comparative experiments on different 
samples of urine, with my method and that of Baron Liebig’s, 
which I believe is considered one of the most accurate of the 
methods of determining urea in urine at present known. 
The following are the results of three comparative experi- 
ments on different samples of urine, using the same with each 
method : — 
Amount of urea in grains and parts of 
a grain in one fluid ounce of urine. 
Liebig’s. New Method. 
Jfirst 3*680 3*712 
Second 5*328 5*472 
Third 4*976 4*976 
In the first and second experiments the quantity of com- 
mon salt present in the urine was taken into account, as it is 
found to increase to a slight extent the apparent quantity of 
urea in the urine by Liebig’s method ; in the third this was 
not taken into consideration, and the quantity of urea was 
compared w T ith the mean of two results obtained by my 
method. 
These experiments show how very closely the results ob- 
tained by the new method agree with those by Baron Liebig’s, 
and therefore show the correctness of the former method. I 
prefer the hypochlorite of soda to that of potash as a decom- 
posing agent, because the soda salt is an article of our 
