By Pror, EMERSON REYNOLDS, M.D. 43 
then replaced in position; the tube D again immersed in the 
water of the large cylinder, and the connexion between E and c 
securely made. Before making the connexion the water in the 
graduated tube should stand at the zero of the scale, but after 
making the joint the pressure within the apparatus is usually 
greater than that without. As the air in the tube D cools down 
to the temperature of the surrounding water, contraction takes 
place; but should the water not return to the zero, equilibrium 
is at once restored by opening the fine india-rubber tube g for a 
few seconds, and then closing in such a manner as to prevent any 
possible escape of gas. 
The hypobromite is brought in contact with the urea solution 
by removing the clip from the india-rubber tube connected with 
the pipette ; the re-agent then falls from a considerable height, 
and mixes thoroughly with the liquid at the bottom of the tube 
D. Nitrogen is evolved and displaces water from c, the water 
being maintained at the same level in both limbs of the U tube 
by allowing the liquid displaced to run off by means of the tap 
T. When the evolution of gas has ceased, the water level is 
adjusted by means of the tap, and the volume of gas produced in 
’ the reaction then read off on the graduated tube ¢; the tem- 
perature of the water in the cylinder B is then ascertained, as 
well as the height of the barometer at the time. From the data 
thus obtained, the volume of dry nitrogen at 0° C. and 760 mm. 
can be easily calculated by the usual formula. 
