94 CHEMICAL PHYSIOLOGY. 



occurs in the urine of birds, reptiles, and mammalia, but it is 

 most abundant in that of carnivora. 



10. Quantity. An adult excretes 30 to 40 grammes (450 to 600 

 grs.) daily ; a woman less, and children relatively more. It 

 varies, however, with 



(a.) Nature of the Food. It increases when the nitrogenous 

 matters are increased in the food, and is diminished by veget- 

 able diet. It is increased by copious draughts of water, 

 salts. It is still excreted during starvation. Muscular 

 exercise has little effect on the amount. 



(b.) In Disease. In the acute stage of fevers and inflam- 

 mations there is an increased formation and discharge, also in 

 saccharine diabetes (from the large quantities of food con- 

 sumed). It is diminished in anaemia, cholera, by the use of 

 morphia, in acute and chronic Bright's disease. If it is re- 

 tained within the body, it gives rise to uraemia, when it may 

 be excreted by the skin, or be given off by the bowel. 



LESSON XVI. 

 VOLUMETRIC ANALYSIS FOR UREA. 



1. Before performing the volumetric analysis for urea, do the 

 following reactions, which form the basis of this process : 



(a.) To a solution of sodic carbonate, add mercuric nitrate 

 = a yellow precipitate of mercuric hydrate. 



(b.) To urine, add sodic carbonate, and then mercuric 



nitrate = first of all a white cheesy precipitate, on adding 



more mercuric nitrate, a yellow is obtained i.e., no yellow 



is obtained until the mercuric nitrate has combined with 



. the urea, and there is an excess of the mercuric salt. 



(c.) To urine add hypobromite of soda. At once the urea is 

 decomposed and bubbles of gas N are given off. 



2. Liebig's Volumetric Process for Urea with Sodic Carbonate as 



