URINE: QUANTITATIVE ANALYSIS. 387 



allow it to cool. Moisten the residue with 1-2 c.c. of water, 1 

 sprinkle about 7-8 grams of sodium peroxide over the contents of 

 the crucible and fuse the mass over an alcohol flame for about 10 

 minutes. Allow the crucible to cool for a few minutes, add about 

 100 c.c. of water to the contents and heat at least one-half hour 

 over an alcohol flame, to dissolve the alkali and decompose the 

 sodium peroxide. Next rinse the mixture into a 400-450 c.c. Er- 

 lenmeyer flask, by means of hot water, and dilute it to about 250 c.c. 

 Heat the solution nearly to the boiling-point and add concentrated 

 hydrochloric acid slowly until the nickelic oxide, derived from the 

 crucible, is just brought into solution. 2 A few minutes boiling 

 should now yield a clear solution. In case too little peroxide or too 

 much water was added f or the final fusion a clear solution will not 

 be obtained. In this event cool the solution and remove the in- 

 soluble matter by filtration. 



To the clear solution add 5 c.c. of very dilute alcohol (about 18- 

 20 per cent) and continue the boiling for a few minutes. The alco- 

 hol is added to remove the chlorine which was formed when the 

 solution was acidified. Add 10 c.c. of a 10 per cent solution of 

 barium chloride, slowly, drop by drop, 3 to the liquid. Allow the 

 precipitated solution to stand in the cold two days and then filter and 

 continue the manipulation according to the directions given under 

 Total Sulphates, page 384. 



Calculation. Make the calculation according to directions given 

 under Total Sulphates, p. 384. Calculate the quantity of sulphur, 

 expressed as SO 3 or S, present in the twenty- four hour urine 

 specimen. 



5. Total Sulphur. Sodium Hydroxide and Potassium Nitrate 

 Fusion Method. Place 25 c.c. of urine in a silver crucible and 

 evaporate to a thick syrup on a water-bath. Add 10 grams of 

 sodium hydroxide and 2 grams of potassium nitrate to the residue 

 and fuse the mass, over an alcohol flame, until all organic matter has 

 disappeared and the fused mixture is clear. Cool the mixture, 

 transfer it to a casserole, by means of hot water, acidify slightly 

 with hydrochloric acid and evaporate it to dryness on a water-bath. 

 Moisten the residue with a few drops of dilute hydrochloric acid 

 and bring it into solution with hot water. Filter, heat the filtrate 

 to boiling and immediately precipitate it by the addition of 10 c.c. 



1 This moistening of the residue with a small amount of water is very essential 

 and should not be neglected. 



2 About 18 c.c. of acid is required for 8 grams of sodium peroxide. 



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



