Rapid Estimation of Urea. 145 



directly, the volume of nitrogen produced thus serving as a 

 measure of the urea from which it was derived. 



The equation which expresses the change just referred to is 

 the following : — 



CO"N s H 4 + 3 (NaBrO) + 2 (NaOH) = 3 NaBr + Na 2 C0 3 



v v ; Sodic^ + 3H 2 + 2N. 



Urea. hypobromite. 



The use of calcic hypochlorite, or solution of " chloride of 

 lime/' in effecting a similar decomposition was pointed out by 

 Dr. E. W. Davy* ; and it has been recently shown by Yvon f 

 that the hypochlorite used by Davy is more effective than the 

 sodic hypochlorite, but it does not evolve the whole of the 

 nitrogen and is irregular in its action. Knop, and after him 

 Hiifnert, and many others, have shown that the sodic hypo- 

 bromite is greatly to be preferred to any of the hypochlorites, 

 as the decomposition of urea is almost complete, and progresses 

 regularly and rapidly without the aid of heat : hence I use 

 the hypobromite as the basis of the plan of operating now to 

 be described, and in this respect agree with Hufner, Russell 

 and West, E,. Apjohn, Blackly, Dupre [and with Simpson 

 and O'Keefe §] in the methods they have proposed for urea- 

 estimation. 



The different methods devised by the above-named chemists 

 all serve for the direct measurement of the volume of nitrogen 

 evolved during the action of the hypobromite on urea, and 

 involve the use of specially graduated tubes for the reception 

 and measurement of the pure gas. My plan is essentially dif- 

 ferent, as the gas evolved, which is scarcely soluble in water || , 

 is made to displace its own volume of that liquid, and the latter 

 is then easily measured in any ordinary vessel, such as a tall 

 and well-graduated drachm measure. 



The apparatus may be most conveniently described as con- 

 sisting of two distinct parts — A, the generating-vessel (see 

 annexed woodcut, fig. 1), and F the small gas-holder, from 

 which water is expelled by the nitrogen entering from A. 



Gas-generating Vessel. — This is an ordinary two-ounce wide- 

 mouthed bottle, fitted with a good india-rubber cork pierced 

 with three holes. Through one of these holes the gas-delivery 

 tube E passes, and through another the small piece of bent 

 * Journal of the Royal Dublin Society, and Phil. Mag. [IV.] vol. vii. 



t Journal de Pharmacie et de Chimie, [4] vol. xxiv. 

 X Journal fur praktische Chemie, [2] vol. iii. p. 1. 

 § Published since this paper was read. 



|| According to Bunsen, water dissolves only 0-01478 of its volume at 

 the mean temperature and pressure (Bunsen's ' Grasometry/ p. 286). 



Phil. Mag. S. 5. Vol. 5. No. 29. Feb. 1878. L 



