URINE 549 



flame is then turned up in two stages to the full heat of the bunsen burner and the 

 contents of the dish thus heated to redness for ten minutes after the black residue 

 (which first fuses) has become dry. This heating is to decompose the last traces of 

 nitrate (and chlorate). The flame is then removed and the dish allowed to cool 

 more or less completely. Ten to 20 c.c. of dilute (i : 4) hydrochloric acid is then 

 added to the residue in the dish, which is then warmed gently until the contents 

 have completely dissolved and a perfectly clear, sparkling solution is obtained. 

 This dissolving of the residue requires scarcely two minutes. With the aid of a 

 stirring rod the solution is washed into 1 a small Erlenmeyer flask, diluted with 

 cold, distilled water to 100-150 c.c., 10 c.c. of 10 per cent barium chloride solution 

 added drop by drop, and the solution allowed to stand for about an hour. It is 

 then shaken up and filtered as usual through a weighed Gooch crucible. Controls 

 should be run on the oxidizing mixture. 



Calculation. Make the calculation according to directions given under Total 

 Sulphates, page 546. Calculate the quantity of sulphur expressed as SO 3 or S, 

 present in the twenty-four-hour urine specimen. 



Interpretation. The total sulphur (80s) excretion averages about 2.5 

 grams per day. It runs more or less parallel with the decomposition 

 of endogenous and exogenous protein and a definite ratio between the 

 excretion of total N and total S might be expected. It has been 

 suggested that the ratio 5 : i expresses this relation in a general way but 

 no constant value can be given. See Total Sulphates. 



5. Total Sulphur. Osborne-Folin Method. Principle. This 

 method depends on the destruction of organic matter by means of 

 sodium peroxide. It is employed particularly for the determination 

 of sulphur in foods and feces. Benedict's procedure (see above) is 

 simpler and fully as satisfactory for urine. 



Place 25 c.c. of urine 2 in a 200-250 c.c. nickel crucible and add about 3 grams of 

 sodium peroxide. Evaporate the mixture to a syrup upon a steam water-bath and 

 heat it carefully over an alcohol flame until it solidifies (15 minutes). Now remove 

 the crucible from the flame and allow it to cool. Moisten the residue with 1-2 c.c. of 

 water, 3 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. Erlenmeyer 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. 4 A few minutes' 

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

 water was added for the final fusion a clear solution will not be obtained. In this 

 event cool the solution and remove the insoluble matter by filtration. 



1 Sometimes the porcelain glaze cracks during heating, in which case the solution should 

 be filtered into the flask. 



2 If the urine is very dilute 50 c.c. may be used. 



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

 should not be neglected. 



4 About 1 8 c.c. of acid are required for 8 grams of sodium peroxide. 



