168 HEALTHY URINE. 



3. Dissolves in KOH, potassium urate being formed, it is 

 re-pp by the addition of 5 pc - HC1 as uric acid. This 

 addition of HC1 to urine causes it to separate out in 

 the form (2). 

 Tests 1 : 



1. Murexide test. To a few drops of urine add a little HNO. { 



evaporate on a porcelain dish without charring, cool and 

 add NH a a purple colour or with KHO a violet 

 murexide. 



2. Schifs test. Dissolve some uric acid crystals 1 provided for 



you in sodium carbonate solution, drop on a filter paper 

 moistened with AgNO.} a black stain of reduced silver 

 results. 



3. Solutions of uric acid or acid urates reduce alkaline copper 



solutions. Use potassium urate obtained by dissolving 

 serpent's excrement in KOH. Part of the Cu 2 O formed 

 unites with any undecomposed uric acid to an insoluble 

 pp of cuprous urate. 



4. To some urine add 5 pc - HC1, let it stand for 24 hours. 



Brown whetstone-shaped crystals separate out as a surface 

 scum and as a deposit. Try the tests on these. 



Urates. Uric acid is a dibasic acid (H 2 U) and forms three 

 kinds of salts. 



(a) Normal urates (M 2 U). These do no occur in the body and 



are laboratory products only. 



(b) Acid or Bi-Urates (MHU) they occur as gouty concretions. 



(c) Quadriurates J %r TT' [ These according to Bence Jones and 



Sir W. Roberts are the physiological salts of uric acid. 



They tend to break up in the presence of water into 

 acid urates and a molecule of additional uric acid. This 



1 Serpent's excrement which consists of nearly pure urate of ammonia may be used 

 with advantage for performing these tests. 



