URINE: QUANTITATIVE ANALYSIS. 389 



6. Total Sulphur. Sherman's Compressed Oxygen Method. 1 

 Evaporate as much urine on an absorbent filter block 2 at 55 C. as 

 the block will conveniently absorb and burn the block so prepared 

 in a bomb-calorimeter 3 using 25-30 atmospheres of oxygen. 

 Connect the bomb with a wash-bottle containing water, and allow 

 the gas to bubble through the liquid until the high pressure within 

 the apparatus has been reduced to atmospheric pressure. Now open 

 the bomb and thoroughly rinse the interior, using water from the 

 wash-bottle for the first rinsing. Dissolve any ash found in the 

 combustion capsule in hydrochloric acid and add this solution to the 

 main solution. Evaporate to 150 c.c., filter and cool the filtrate. 

 Add 10 c.c. of a 5 per cent solution of barium chloride to the cold 

 filtrate, slowly, drop by drop. 4 The contents of the flask should not 

 be stirred or shaken during the addition of the barium chloride. 

 Allow the mixture to stand at least one hour, then shake up the 

 solution and filter it through a weighed Gooch crucible. Manipu- 

 late the precipitate of BaSO 4 according to directions given under 

 Total Sulphates, page 384. 



Calculate the quantity of sulphur, expressed as SO 3 or S, present 

 in the twenty- four hour urine specimen. 



IX. Phosphorus. 



i. Total Phosphates. Uranium Acetate Method. To 50 c.c. 

 of urine in a small beaker or Erlenmeyer flask add 5 c.c. of a special 

 sodium acetate solution 5 and heat the mixture to the boiling-point. 

 From a burette, run into the hot mixture, drop by drop, a standard 

 solution of uranium acetate until a precipitate ceases to form and 



1 See Sherman's Organic Analysis, p. 19. 



2 Only a small amount of urine should be added at one time, it being necessary 

 to make several evaporations before the block contains sufficient urinary residue 

 to proceed with the combustion. 



3 The Berthelot-Atwater apparatus (Fig. 124, page 388) is well adapted to this 

 purpose. 



4 See note (2) at the bottom of page 384. 



5 The sodium acetate solution is prepared by dissolving 100 grams of sodium 

 acetate in 800 c.c. of distilled water, adding 100 c.c. of 30 per cent acetic acid to 

 the solution and making the volume of the mixture up to i liter with water. 



This uranium acetate solution may be prepared by dissolving 35.461 grams 

 of uranium acetate in one liter of water. One c.c. of such a solution should be 

 equivalent to 0.005 gram of P 2 O 5 , phosphoric anhydride. This solution may be 

 standardized as follows : To 50 c.c. of a standard solution of disodium hydrogen 

 phosphate, of such a strength that the 50 c.c. contains o.i gram of P 2 O 5 , add 

 5 c.c. of the sodium acetate solution, mentioned above, and titrate with the 

 uranium solution to the correct end-reaction as indicated in the method proper. 



