ADVANCED PHYSIOLOGICAL CHEMISTRY 461 



cork being fitted into the month of the flask and being doubly bored, 

 one hole for the filter funnel, the other for a tube connected with a 

 suction pump. By this means, also, a large amount of the alcohol and 

 ether is removed through the pump. 



Hippuric Acid. The quantitative determination of this body is 

 exceedingly difficult, and consists of extracting it by means of alcohol 

 and ether from urine made alkaline with sodium carbonate. 



CHAPTEE XL 

 URINE CONTINUED. 



Chemical Reactions which show the Relationship of Uric Acid to 

 Urea. By Analysis. If uric acid be carefully oxidised in acid solution 

 (i.e. by treating it with cold concentrated nitric acid) it decomposes into 

 alloxan and urea : 



NH-CO NH-CO 



CO C-NHv + H 0+0=CO CO + NH 9V 



I II >co i I ~>co. 



NH-C-NH/ NH CO NH/ 



(uric acid) (alloxan) (urea) 



If the oxidation be more energetic (as by using warm nitric acid) the 

 alloxan is further split up into parabanic acid and carbonic acid gas: 

 NH-CO NH-CO 



CO CO+0=CO 



NH-CO NH-CO + C0 2 . 

 (alloxan) (parabanic acid) 



If now parabanic acid be caused to take up a molecule of water (by 

 heating it with alkalies) it changes into oxaluric acid 

 NH-CO NH-CO 



CO 



I 



NH-CO NH 2 COOH. 



(parabanic acid) (oxaluric acid) 

 By prolonged boiling with water this is split up into oxalic acid and 



urea : 



NH-CO 



CO 



I 



NH 2 COOH 

 \NH 2 COOH 



NH 2 COOH 

 (oxaluric acid) (urea) (oxalic acid) 



