UREA IN THE URINARY SECRETIONS. 679 
steady cup or small mortar. The mercury then flows out, 
and the solution of salt takes its place, and the mixture of 
urine and hypochlorite being lighter than the solution of salt, 
w 7 ill remain in the upper part of the tube, and will therefore 
be prevented from descending and mixing jvith the fluid in 
the cup. A rapid disengagement of minute globules of gas 
soon takes place in the mixture in the upper part of the tube, 
and the gas is there retained and collected. 
The tube is then left in the upright position, till there is 
no further appearance of minute globules of gas being 
formed ; the time being dependent on the strength of the 
hypochlorite and the quantity of urea present ; but the de- 
composition is generally completed in from three to four 
hours. It may, however, be left much longer, even for a 
day, if convenient, and having set the experiment going, it 
requires no further attention ; and when the decomposition 
is completed, it is only necessary to measure the quantity of 
gas produced, by transferring it into a graduated tube or 
measure. 
I have generally used a graduated tube in the first instance, 
as it saves the trouble of transferring the gas, and incurring 
the risk of losing some of it in the process. 
That which I would recommend as being convenient for 
this purpose, is a stout tube having a bore of half an inch in 
diameter, and capable of holding from two to three cubic 
inches. A tube having this bore, and about fourteen inches 
in length, will hold two-and-a-half cubic inches, which will be 
quite large enough. Each cubic inch of it should be divided 
into tenths and hundredths of a part of a cubic inch. It is 
scarcely necessary to remark, that in cases where great accu- 
racy is required, due attention must be paid to the tempera- 
ture and atmospheric pressure, and certain corrections made 
if these should deviate from the usual standards at the time 
of reading off the volume of the gas ; but in most cases, suf- 
ficiently near approximations to accuracy may be obtained 
without reference to these particulars. 
From a number of experiments I have ascertained that 
the quantity of gas evolved from different amounts of urea 
(treated in the way I have described), very closely approxi- 
mates to the quantity of nitrogen gas which should be fur- 
nished from the urea by calculation. 
This will be seen from the following experiments taken 
from many : 
The fifth part of agrain of urea should furnish by calculation, 
0-3098 parts of a cubic inch of nitrogen gas, at 60° Fahr. and 
30' Bar. ; the same quantity of urea, treated, as described, 
