54 



woman less, and children relatively more. Its amount 

 varies with the nature of the food ; it is increased when the 

 nitrogenous matters of the food are increased and is dimin- 

 ished by vegetable diet ; increased by copious draughts of 

 water, salts. Saccharine diabetes and acute stages of fever 

 increase its discharge. Bright's disease, anemia, cholera 

 and the use of morphine decrea.se it. If retained in the 

 body it gives rise to uremia, when it may be excreted by 

 the skin or given off by the bowel. 



254. Uric acid (CsH^N^O,) contains 33.33% of nitrogen 

 and, next to urea, is the constituent of the urine whereby 

 the largest quantity of nitrogen of the body is excreted, 

 whilst in birds, reptiles and insects it forms the chief nitro- 

 genous excretion. The proportion of urea to uric acid is 

 45 to I. About 0.5 gram of uric acid is excreted daily in 

 man. This quantity is diminished in gout, etc. Uric acid 

 causes the brick-red deposit .sometimes seen in urine after 

 standing for a time. 



255. In a conical glass, add 5 parts of hydrochloric acid 

 to 20 parts of urine. I,abel and put in a cool place for 24 

 hours. Yellow or brownish colored crystals of uric acid are 

 deposited on the sides of the glass, or form a pellicle on the 

 .surface of the fluid like fine grains of cayenne pepper. 

 Examine some of the crystals microscopically. 



256. Murexide test. Place a little uric acid in a porce- 

 lain capsule, add nitric acid and heat gentl}', not above 

 40° C. A yellow or reddish .stain remains. Allow it to 

 cool and bring a rod dipped in ammonia near the stain, and 

 if this produces no effect, moisten the .stain with strong am- 

 monia ; a purple red color of murexide or purpurate of 

 ammonia is formed. It turns bluer upon the addition of 

 caustic potash. 



257. Di.ssolve a little uric acid in 10% caustic .soda or 

 potash. Add a drop or two of Fehling's solution — or dilute 

 cupric sulphate and caustic potash — a precipitate which at 

 first mas' be white and after a time turning green or reddish. 



