628 APPENDIX 



olism and is also the medium in which the accessories of the diet 

 are discharged from the body. 



The chief end-products of protein metabolism are urea, creatinin, 

 uric acid, and ammonia. Among the chief excreted accessories are 

 (a) inorganic: water, and sodium, potassium, calcium, and mag- 

 nesium chlorides, sulphates, and phosphates; (b) organic: non- 

 nutrient constituents of food which serve to give it flavor; drugs. 

 Examples of this class of excreta are the purin bodies, which rep- 

 resent the excreted alkaloids of tea, coffee, and cocoa; and the 

 substance which gives urine its peculiar odor after the eating of 

 asparagus. 



Test for Urea. To 15 c.c. of urine add J^ its volume of baryta 

 mixture to remove inorganic constituents which would interfere 

 with the test. Filter. To a portion of the filtrate add a solution 

 of mercuric nitrate, a precipitate forms which is a compound of 

 urea and mercury. 



Test for Creatinin. To 8 c.c. of urine add 2 c.c. of a solution of 

 sodium nitro-prussiate, then 1 c.c. NaOH; a red color appears. 

 Boil the solution. The color fades; while boiling add about 1 c.c. 

 of acetic acid; the color changes to blue. 



Test for Ammonia. To 4 c.c. of fresh urine in a test tube add a 

 little dry sodium carbonate. Heat. Hold in the neck of the test 

 tube, without touching the sides, a strip of moistened, neutral 

 litmus paper. The blue coloration shows the presence of ammonia 

 gas. 



Test for Chlorides. To 4 c.c. of urine add an excess of nitric 

 acid (HNO 3 ), then a drop or two of silver nitrate solution (AgNO 3 ). 



Test for Sulphates. Add to 4 c.c. of urine a few drops of barium 

 chloride solution and then an excess of HC1. The latter redis- 

 solves the phosphates, leaving the sulphate of barium alone in 

 the precipitate. 



Test for Phosphates. Make 10 c.c. of urine alkaline with am- 

 monium hydroxide (NH 4 OH). Heat. The precipitate that forms 

 is a mixture of calcium and magnesium phosphates. Filter. To 

 the filtrate add a small amount of magnesia mixture (MgS0 4 , 

 NH 4 C1, and NH 4 OH in water). Heat. The precipitate is due 

 to the presence of sodium, potassium, and ammonium phosphates. 



Test for Purin Bodies. Add to 10 c.c. of urine an excess of 

 magnesia mixture. Filter off the precipitate of phosphates. Add 



