ANALYSIS OF URINE 541 . 



Sulphates. 



Sulphur is present in urine in three forms : 



(1) Inorganic sulphates. 



(2) Ethereal sulphates. 



(3) Neutral sulphur. 



The sulphates are derived mainly from the sulphur in the protein ; 

 the amount of sulphate in the food is small. The average amount of 

 sulphate in urine is 2-5 to 3-0 gm. per day. It varies directly with 



that of the nitrogen. The value of is about 5. The ethereal 



hl 2 bU 4 



sulphates increase in amount when putrefactive changes occur in the 

 intestine or if poisonous substances, such as phenol, be taken. It is 

 often of great importance to know the relative amounts of inorganic 

 and ethereal sulphates. 



The neutral sulphur consists of cystine, thiocyanates, sulphides and 

 other substances. The estimation of the various forms of sulphur is 

 effected by determining (i) the amount of inorganic sulphate, (2) the 

 amount of ethereal sulphate, after removal of the inorganic sulphate, by 

 hydrolysis to inorganic sulphate, or by hydrolysis of the ethereal sul- 

 phate and determination of the inorganic and ethereal sulphate together 

 and taking the difference, (3) the estimation of the total sulphates after 

 oxidising the neutral sulphur to sulphate. The difference between this 

 amount and that of inorganic + ethereal is the amount of neutral sulphur. 



Gravimetric Estimation. 



The usual and most accurate method of determining the various 

 forms of sulphur in urine is gravimetric. The following procedure of 

 Folin is the one usually adopted : 



(i) Ethereal + Inorganic Sulphates. 



5 c.c. of 4 per cent, potassium chlorate solution and 5 c.c. of concen- 

 trated hydrochloric acid are added to 50 c.c. of urine in a 200 c.c. conical 

 flask. The mixture is boiled for 5-10 minutes so as to hydrolyse the 

 ethereal sulphates and to oxidise the pigments of the urine. The solution 

 becomes colourless. 25 c.c. of 10 per cent, barium chloride solution are 

 slowly dropped in through a funnel with a capillary point. The solution is 

 kept just below the boiling-point for |-i hour. The barium sulphate is filtered 

 off on filter paper, washed for half an hour with hot water, at intervals of a few 

 minutes hot 5 per cent, ammonium chloride being substituted for the water, so 

 that in all five or six additions of ammonium chloride take place in the course 

 of the first twenty minutes' washings. The filter and precipitate are dried by 

 folding and pressing gently between dry filter papers and are transferred to a 

 weighed crucible; 3 or 4 c.c. of alcohol are poured into the crucible and 

 ignited. This dries and partially burns the filter paper. The residue is heated 

 to whiteness, cooled and weighed. 



The barium sulphate may also be collected on a Gooch crucible. 



