566 PHYSIOLOGICAL CHEMISTRY 



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 1 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 i -2 c.c. of 

 water, 2 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. 3 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. 



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 alcohol 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, 4 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 Sul- 

 phates, page 563. 



Calculation. Make the calculation according to directions given under Total 

 Sulphates, page 563. Calculate the quantity of sulphur, expressed as SO 3 or S, 

 present in the twenty-four-hour urine specimen. 



Interpretation. See page 565. 



(b) Volumetric Procedures 



6. Volumetric Determination of Ethereal and Inorganic Sulphates. 

 Method of Rosenheim and Drummond. 5 Principle. The sulphates 

 of the urine are precipitated by means of benzidine solution, the pre- 



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



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

 should not be neglected. 



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



4 See note (2) at the bottom of p. 563. 



5 Rosenheim and Drummond: Biochem. J., 8, 143, 1914. 



