192 QUANTITATIVE ANALYSIS. 



to 40-50 and 30 g. of ammonium chloride dissolved therein. 

 The precipitate of ammonium urate is filtered off after stand- 

 ing for one-half to one hour and washed free from chlorine 

 with a 10 per cent, ammonium sulphate solution; then it is 

 dissolved on the filter in hot 1 to 2 per cent, sodium hydroxide 

 solution, the filter washed with hot water, and the filtrate 

 and wash-water heated in a porcelain dish on the water-bath 

 until all the ammonia has been driven off. The alkaline 

 uric acid solution is rinsed into a Kjeldahl flask, stirred up 

 with 15 cc. of concentrated sulphuric acid, some copper sul- 

 phate and potassium sulphate added, and the ammonia 

 resulting estimated in the usual way. 



One cubic centimeter of the fifth-normal hydrochloric 

 acid corresponds to 8.4 mg. of uric acid. The heating of 

 the alkaline uric acid solution may also be done in a large 

 Kjeldahl flask, but then constant attention is necessary since 

 loss may easily occur from foaming. In this case the entire 

 detennination may be carried to completion in the same 

 flask. 



IV. DETERMINATION OF CREATININE AS CREATININE ZINC 



CHLORIDE. 



In this determination we proceed exactly as in the method 

 given for the detection of creatinine, see page 102, using 80 

 cc. of the alcoholic filtrate for the precipitation with zinc 

 chloride. The creatinine zinc chloride which separates is 

 collected on a dried and weighed filter, as in the case of uric 

 acid, washed with alcohol until the wash-liquid no longer gives 

 the reaction for chlorides, dried and weighed. The amount 

 obtained when multiplied by 0.39 gives the percentage of 

 creatinine. (One hundred parts of creatinine zinc chloride 



6242 X 5 

 correspond to 62.42 of creatinine, hence g - = in round 



numbers 0.39.) 



