SI 



first cubic centimeter may be more accurately read and 

 measured. Above the graduated scale the tube possesses 

 sufBcient capacity for the reception of the reagents. After 

 use, the tube must be thoroughly but carefully cleaned. 



In operating the centrifuge the tubes are to be revolved 

 for exactly three minutes and at as uniform rate as possible. 

 The ungraduated tube may be filled with water or urine and 

 the revolutions will cause a deposit to form at the bottom, in 

 the case of the urine. 



243. Chlorides. Fill the graduated tube to the 10 cc. 

 mark with the urine to be tested. Add 15 drops of nitric 

 acid to prevent precipitation of the pho.sphates ; then fill to 

 the 15 cc. mark with the silver nitrate solution. Close and 

 invert the tube several times so that the reagents are thor- 

 oughly mingled. Revolve for three minutes at 1000 revolu- 

 tions per minute when the quantity in bulk percentage maj' 

 be read off from the graduated scale on the side of the tube. 

 The percentage thus obtained ranges from 10% to 12% for 

 normal human urine. 



244. Sulphates. These are estimated as insoluble salts of 

 barium. Fill the tube as before to the 10 cc. mark. Add 

 15 drops of hydrochloric acid to prevent precipitation of 

 pho.sphates. Fill to the 10 cc. mark with barium chloride 

 and after inverting the tube a few times, revolve for three 

 minutes. The bulk percentage is obtained as before and is 

 found to be about 0.8 % in normal human urine. 



245. Phosphates. Fill with urine to the 10 cc. mark and 

 add enough of the magnesium mixture to reach 15 cc. In- 

 vert the tube several times and revolve three minutes. Read 

 off the bulk percentage which in normal human urine is 

 found to be about 8 % . 



