Determination of Uric Acid. 



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reagent for uric acid, presumably because of impurities such as 

 nitrates and molybdates. The tungstate which we have in our 

 laboratory failed to give the reagent although free from the im- 

 purities mentioned above. Further investigations, however, dis- 

 closed that our sodium tungstate contained but one third tung- 

 state the rest being sodium carbonate. The reagent was there- 

 fore prepared in the following manner: 



Dissolve 25 g. of sodium tungstate in 300 c.c. of water, heat 

 to boiling in a large beaker, add 40 c.c. of cone, hydrochloric acid 

 whereupon the tungstic acid is precipitated. Continue to boil 

 for ten minutes. Allow to settle. Filter by suction. Wash pre- 

 cipitate with cold water while still in Buchner funnel, 20 c.c. each 

 time, discontinuing as soon as the precipitate starts to pass 

 through the filter, which usually occurs at the third washing. 

 Transfer to an Erlenmeyer flask without drying the precipitate. 

 Add 15 c.c. of 10 per cent, sodium hydroxide solution for each 

 ten g. of tungstic acid, which will dissolve the tungstic acid on 

 heating. 



Continue according to instructions given for the preparation 

 of reagent using but 31.2 g. of tungstic acid in place of 100 g. of 

 sodium tungstate as required in the original description of the 

 reagent. 



In our search for the explanation of the failure to obtain the 

 reagent we had to limit ourselves to the use of the two tungstates 

 in stock in our store-room; one of them free from carbonate gave 

 the reagent, the other containing carbonate failed to do so. We 

 are postponing the investigation, to determine if any tungstate 

 free from carbonate will react in the desired manner, until the 

 substance is more accessible. The writers regret that they were 

 also unable to procure tungstic acid itself which they believe could 

 be used in place of the tungstate, by dissolving the acid in a slight 

 excess of sodium hydroxide followed by the procedure given above* 



It is necessary to establish the content of actual tungstate only 

 once in order to know how much sodium hydroxide solution has 

 to be added. This is accomplished by transferring the tungstic 

 acid precipitate to a weighed porcelain dish. After drying the 

 contents on a waterbath and subsequent washing with alcohol the 

 dish is weighed again. For preparing the reagent, however, the 

 isolation of the sodium salt is unnecessary. 



