URINE 



517 



urates and uric acid. The method does not give an absolutely accurate measure 

 of the purine values. It is, however, of considerable service clinically. The 

 principle of the method is the preliminary precipitation of 

 the phosphates present followed by the precipitation of the 

 purine bodies in the form of their silver compounds by means 

 of an ammoniacal silver nitrate solution. The volume of this 

 silver precipitate is then determined and its nitrogen value 

 interpolated by means of a table of equivalent values. 



Procedure. Collect the 24-hour urine and mix it 

 thoroughly. Take 100 c.c. of the urine and if albumin is 

 present make slightly acid with acetic acid and boil and filter. 

 Close the stopcock of the instrument and introduce 90 c.c. 

 of urine and 20 c.c. of a modified magnesia mixture. 1 Turn 

 the stopcock and permit the precipitated phosphates to pass 

 into the lower chamber of the instrument. After an interval 

 of ten minutes has elapsed the stopcock should be closed 

 and sufficient ammoniacal silver nitrate solution 2 added to 

 make the total volume in the upper chamber 100 c.c. The 

 precipitate of the silver compounds of the purine bodies 

 should be pale yellow. Any silver chloride present may be 

 brought into solution in the strong ammoniacal solution by 

 the repeated inversion of the purinometer. In case the 

 chloride does not dissolve it should be brought into solution 

 by the addition of further ammonium hydroxide. Place the 

 purinometer in a dark room for 24 hours and at the end of 

 this time read the volume of the purine precipitate. Inter- 

 polate the value in terms of purine nitrogen by means of the following table: 



Precipitate, Purine nitrogen, 



c.c. per cent 



(grams in 100 c.c.) 

 4 0.0078 



5 0.0097 



6 0.0117 



7 0.0136 



8 0.0156 



.9 0.0175 



10 0.0185 



ii 0.0195 



12 O. 0205 



13 0.0218 



14 O.O225 



15 0.0234 



16 0.0249 



17 0.0260 



18 0.0265 



19 0.0270 



1 This is prepared as follows: Dissolve 10 grams of magnesium chloride in about 75 c.c. 

 of water and add TO grams of ammonium chloride. Introduce 100 c.c. of concentrated 

 ammonium hydroxide into this mixture. If a precipitate forms add ammonium hydroxide 

 until a clear solution is obtained. Make the volume 200 c.c. by means of water and add 10 

 grams of purified talcum. 



2 This solution has the following formula: 



Silver nitrate i gram. 



Ammonium hydroxide (sp. gr. 0.90) 100 c.c. 



Talcum 5 grams. 



Distilled water 100 c.c. 



FIG. 1 66. HALL'S 

 PURINOMETER. 



