564 PHYSIOLOGICAL CHEMISTRY 



From 75 to 95 per cent of the total sulphur of the urine is ordinarily 

 found as sulphate, the proportion being greatest on a high protein diet. 

 The sulphate excretion is increased in all conditions associated with 

 increased decomposition of body protein as in acute fevers and de- 

 creased whenever there is a decrease in metabolic activity. 



2. Inorganic Sulphates. Folin's Method. Place 25 c.c. of urine and 100 

 c.c. of water in a 200-250 c.c. Erlenmeyer flask and acidify the diluted urine 

 with 10 c.c. of dilute hydrochloric acid (i volume of concentrated HC1 to 4 vol- 

 umes of water). In case the urine is dilute 50 c.c. may be used instead of 25 c.c. 

 and the volume of water reduced proportionately. Add 10 c.c. of 5 per cent bar- 

 ium chloride slowly, drop by drop, to the cold solution and from this point proceed 

 as indicated in the method for the determination of Total Sulphates, page 562. 



Calculate the quantity of inorganic sulphates, expressed as SOs, in the twenty- 

 four-hour urine specimen. 



Calculation. Calculate according to the directions given under Total Sul- 

 phates, above. 



Interpretation. On an average about 90 per cent of the total sul- 

 phates of the urine exists as inorganic sulphates but the proportion 

 of the sulphates existing in this form varies widely, being greater on 

 a high protein diet than on a very low protein diet. The amount 

 varies with the total sulphates (which see). 



3. Ethereal Sulphates. Folin's Method. Principle. The inorganic sul- 

 phates are removed with barium chloride and the conjugated sulphates then 

 determined after hydrolysis. 



Procedure. Place 125 c.c. of urine in an Erlenmeyer flask of suitable size, 

 dilute it with 75 c.c. of water and acidify the mixture with 30 c.c. of dilute hydro- 

 .chloric acid (i volume of concentrated HC1 to 4 volumes of water). To the cold 

 solution add 20 c.c. of a 5 per cent solution of barium chloride, drop by drop. 1 

 Allow the mixture to stand about one hour, then filter it through a dry filter paper. 2 

 Collect 125 c.c. of the filtrate and boil it gentry for at least one-half hour. Cool 

 the solution, filter off the precipitate of BaSO4, wash, dry and ignite it according to 

 the directions given on page 563. 



Calculation. The weight of the BaSO4 precipitate should be multiplied by 

 2 since only one-half (125 c.c.) of the total volume (250 c.c.) of fluid was precipi- 

 tated by the barium chloride. The remaining calculation should be made accord - 

 ing to directions given under Total Sulphates, page 563. 



Calculate the quantity of ethereal sulphates, expressed as SO 3 , in the twenty- 

 four-hour urine specimen. 



Interpretation. The excretion of ethereal sulphates (expressed as 

 SOs) varies ordinarily from o.i to 0.25 gram per day comprising from 



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



1 This precipitate consists of the inorganic sulphates. If it is desired, this BaSO4 

 precipitate may be collected in a Gopch crucible or on an ordinary quantitative filter 

 paper and a determination of inorganic sulphates made, using the same technic as that 

 suggested above. In this way we are enabled to determine the inorganic and ethereal 

 sulphates in the same sample of urine. 



