328 



ANALYSIS OF URINE. 



[CH. XIII. 



is about i inch from the exit tube B. This minimises the risk of any 

 alkali being carried over by spurting. This risk, however, has been 



found to be so small that it is hardly 

 worth the trouble of fitting. B is 

 joined to the tube to the condenser 

 by a short piece of rubber tubing. 

 This allows the operator to shake A, 

 and, by removing the strain, de- 

 creases the risk of breaking the 

 glass parts. The standard acid is 

 measured into E, a 250 cc. Erlen- 

 meyer flask. 20 cc. of o-i N. acid 

 is usually ample. The wooden 

 blocks, F, should be so arranged 

 that the lower end of D only just 

 dips below the surface of the acid. 

 Now remove A and run in 13 or 

 14 cc. of 40 per cent, soda, running 

 this gently down the lower part of 

 the neck and sides of the flask, so 

 that the soda sinks to the bottom 

 of the fluid and the risk of the loss of 

 ammonia is minimised. The flask 

 should be held in a nearly horizontal 

 position during this operation; it 

 should be raised to the vertical caut- 

 iously, so as to prevent mixing of the 

 two layers. Re-assemble the appa- 

 ratus, seeing that the two rubber 



stoppers are firmly held. Have ready a Bunsen burner, with a 

 rose-top, and a screw clip, H, fitted to the rubber tubing. See 

 that the adjustable stand for the burner is at such a height that the 

 top of the rose is about half an inch under the bottom of the flask. 

 Turn on the water supply to the condenser. Unclamp the flask A 

 and mix its contents by shaking, taking care that the rubber stoppers 

 are not loosened. Place the burner in position and gently agitate 

 the flask until the fluid commences to boil. The flask can then be 

 clamped and the distillation allowed to continue for 15 minutes. 



Fig. 42. Kjeldahl's method. 



Cole's apparatus for alcohol 

 distillation. 



