278 PHYSIOLOGICAL CHEMISTRY 



and set aside over night. Examine the sediment under the 

 microscope and note the diagonally crossed crystals of calcinm 

 oxalate. 



(f) Urinary Indican. Indican is usually, but not always, 

 found in the urine. It is formed from the products of protein 

 putrefaction in the intestine. To 15-20 c.c. urine in a test tube 

 add 2 c.c. copper sulphate solution, 15 or 20 c.c. cone. HC1 and 

 5 c.c. chloroform. Close the mouth of the tube with the thumb 

 and shake cautiously (over the sink). Continue the shaking for 

 several minutes. The ' ' indican ' ' is oxidized to indigo, which dis- 

 solves in the chloroform, giving it a blue color. The depth of 

 color developed in the chloroform indicates roughly the amount 

 of indican present. 



(g) PIGMENTS. Urochrome and uroerythrin are the most im- 

 portant urinary pigments. 



(1) Urochrome is a substance which gives the yellow color to 

 urine. 



(2) Uroeryfhrin. This red pigment gives the deep reddish 

 color to sediments of uric acid and urates. To highly colored 

 urine add lead acetate solution, and allow to stand. In the pres- 

 ence of uroerythrin the precipitate will be a beautiful pink 

 color. 



Uroerythrin in amounts sufficient to give a strong test occurs 

 somewhat rarely ; in case your specimen gives a good test, hand 

 the test tube to an instructor so that it may be exhibited to the 

 class. 



(h) In addition to the above constituents the urine contains 

 small and varying amounts of various substances, e.g., hippuric 

 acid, allantoin, aromatic oxyacids, compounds containing sulphur 

 and many other substances. 



2. Collection and Preservation of a Specimen for Quantitative 

 Analysis General Properties 



As the composition of the urine voided at different times of 

 the day varies considerably, it is customary to use for metabolism 

 studies a complete 24-hour sample. This may be obtained as 



