On a new Method for the Determination of Urea. 291 



Fig. 1. 



the cork a second 

 tube, c, to convey 

 away the carbonic 

 acid which arises. 



Attached to the 

 last-mentioned tube 

 by means of caout- 

 chouc connecters are 

 two little WoulfVs 

 bottles, d and e, each 

 of about 50 cubic 

 centimetres capacity. 

 These are to be half- 

 filled with a solution composed of a saturated solution of baryta 

 water, diluted with its volume of water. The exit tube, /, of the 

 last WouhVs bottle is connected with an aspirator, g. 



The aspirator is set in action, and the tightness of the joints 

 proved by the passage of air-bubbles at the proper places. 

 Then through the funnel b, the nitroso-nitric acid is poured. A 

 brisk effervescence instantly takes place in the urine, and the 

 flow of water from the aspirator is so regulated that there is a 

 constant succession of air-bubbles escaping from the end of the 

 funnel-tube, b, through the urine, and no carbonic acid gets out 

 through that tube into the atmosphere. The decomposition 

 should not be permitted to go on too fast. As the effervescence 

 declines, more nitroso-nitric acid is added, and a slight gyrating 

 motion given to the flask, a, by the hand, the flexible connecter 

 at c permitting this to be done. 



This motion being persisted in for a few minutes, the air 

 which is continually entering through the funnel-tube and pass- 

 ing in bubbles through the urine, finally removes from that liquid 

 every vestige of carbonic acid. We know that this has taken 

 place by its ceasing to sparkle on a momentary cessation of the 

 motion, and that enough acid has been added by no minute 

 bubbles being generated on the addition of a small quantity 

 more. 



The carbonic acid arising from the destruction of the urea is 

 drawn by the aspirator through the baryta water, and the car- 

 bonate of baryta subsides. The vapours of nitrous or nitric acid 

 drawn over form soluble salts. At the close of the decomposition 

 150 cubic centimetres of air are rapidly run through by the 

 aspirator, to remove any remaining carbonic acid from the 

 bottle a. 



The carbonate of baryta is next to be washed and weighed. 

 The details are as follows : — 



A tin-plate cup, 3^ inches high and %\ in diameter, aa, fig. 2, 



U2 



