152 On the Rapid Estimation of Urea. 



apparatus measures 60 centims. in length. The graduation 

 cannot be conveniently carried beyond fifths of a cubic cen- 

 timetre. At the point shown an india-r ubber tube g is attached, 

 which can be closed at will either by a good clip or by a 

 stopper of glass rod. The glass side-tube c serves to connect 

 the measuring-apparatus in the manner shown with the gene- 

 rating- vessel D, which is a long and wide glass tube placed 

 within the cylinder. The glass T-tube E is connected by 

 means of rubber tubing with c, while one limb passes through 

 the india-rubber cork of D, and the other is connected by 

 another piece of rubber tubing with the fine tube of the long 

 pipette F (of about 20 cubic centims. capacity) which pro- 

 jects through the cork. This connexion must be sufficiently 

 long to admit of the clip being applied as shown. 



The large glass cylinder B is filled with water in order to 

 maintain a steady temperature, the value of which can be 

 known by means of a thermometer immersed in the water. 



A determination is made with this apparatus in the following 

 way: — Having disconnected the T-tube E from c and the clip, 

 the generating-tube D is taken out of the water of the cylinder, 

 the cork carrying the pipette, &c. withdrawn, and then 5 cubic 

 centimetres of the urea solution introduced into the tube D. 

 Before replacing the cork the pipette F is filled with hypo- 

 bromite solution by suction above E, while the small glass 

 tube opening on the underside of the cork is closed by a 

 finger ; the clip is then applied. The exterior of the pipette 

 is now washed with a little water, and the cork, with the ap- 

 paratus attached, is 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 into contact with the urea solu- 

 tion by removing the clip from the india-rubber tube connected 

 with the pipette ; the reagent 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. 



