URINE. 2/3 



When pure, uric acid may be obtained as a white, odorless, and 

 tasteless powder which is composed principally of small transparent 

 crystalline rhombic plates. Uric acid as it separates from the urine 

 is invariably pigmented, and crystallizes in a large variety of char- 

 acteristic forms, e. g,, dumb-bells, wedges, rhombic prisms, irregu- 

 lar rectangular or hexagonal plates, whetstones, prismatic rosettes, 

 etc. Uric acid is insoluble in alcohol and ether, soluble with diffi- 

 culty in boiling water (1:1800) and practically insoluble in cold 

 water (1:39,480, at 18 C.). It is soluble in alkalis, alkali car- 

 bonates, boiling glycerol, concentrated sulphuric acid and in cer- 

 tain organic bases such as ethylamine and piperidine. It is claimed 

 that the uric acid is held in solution in the urine by the urea and 

 disodium hydrogen phosphate present. Uric acid possesses the 

 power of reducing cupric hydroxide in alkaline solution and may 

 thus lead to an erroneous conclusion in testing for sugar in the urine 

 by means of Fehling's or Trommer's tests. A white precipitate of 

 cuprous urate is formed if only a small amount of cupric hydroxide 

 is present, but if enough of the copper salt is present the character- 

 istic red or brownish-red precipitate of cuprous oxide is obtained. 

 Uric acid does not possess the power of reducing bismuth in alka- 

 line solution and therefore does not interfere in testing for sugar 

 in the urine by means of Boettger's or Nylander's tests. 



In addition to being an important urinary constituent uric acid is 

 normally present in the brain, heart, liver, lungs, pancreas and 

 spleen; it also occurs in the blood of birds and has been detected in 

 traces in human blood under normal conditions. 



Pathologically, the excretion of uric acid is subject to wide vari- 

 ations but the experimental findings are rather contradictory. It 

 may be stated with certainty, however, that in leukaemia the uric 

 acid output is increased absolutely as well as relatively to the urea 

 output; under these conditions the ratio between the uric acid and 

 urea may be as low as 1:9, whereas the normal ratio, as we have 

 seen, is i : 50 or higher. In the study of the influence of 

 X-ray on metabolism Edsall has very recently reached some in- 

 teresting conclusions. He found that the excretion of uric acid is 

 usually increased and that in some conditions, particularly in 

 leukaemia, it may be greatly increased. The excretion of total 

 nitrogen, phosphates and other substances may also be considerably 

 increased. 



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