282 URINE. [CH. XII 



The proportion of the sulphur that is present as ethereal 

 sulphate varies considerably Folin has shewn that in 

 starvation and on diets relatively deficient in proteins the 

 proportion increases, as does that of the "neutral" sulphur. 

 There is also a marked increase after the administration of 

 certain phenolic substances, or when such compounds are 

 formed in the body by bacterial decomposition, as in 

 intestinal obstruction and severe constipation. In such 

 cases the phenols found conjugated with sulphuric acid are 



C 6 H 5 .OH ............... phenol 





...... p - cresol 



fr m tyrosine ' 



C 9 H 6 N.OH ............ indoxyl, formed from tryptophane. 



These bodies are poisonous. They unite with sulphuric 

 acid, probably in the liver, to form the innocuous ethereal 

 sulphates. 



The ethereal sulphates form soluble barium and 

 benzidine salts, and can be separated from the inorganic 

 sulphates by treatment with barium chloride or benzidine 

 hydrochloride and filtering. They are hydrolysed to the 

 phenol and sulphuric acid by boiling with hydrochloric acid. 



"Neutral" Sulphur. In urine there is always present a 

 certain amount of sulphur in a form less oxidised than 

 that of a sulphate. The exact nature of the compounds 

 in urine containing sulphur in this form is not yet clear. 



It is probable that the amount of "neutral" sulphur 

 in the urine is independent of the total amount of sulphur 

 excreted. It probably varies with the amount of tissue 

 protein metabolised, so that its determination is often of 

 considerable interest. 



For the percentages of sulphur excreted in the three 

 forms under different metabolic conditions see page 270. 



For the methods of determination of the sulphur see 

 pages 355358. 



Phosphates. The phosphates of the urine are present 

 on the one hand as salts of the alkali metals and of 



