170 PHYSIOLOGICAL CHEMISTRY 



Phosphates. The urine contains about 0.5-1.2 grams phos- 

 phorous per day, but none of this is in the form of free phos- 

 phorus. It all is in oxidized form as phosphates, a portion of 

 which are present as mono- or di-sodium, potassium, calcium or 

 magnesium phosphates, some probably as free phosphoric acid, 

 and some in ester-like compounds such as glycero-phosphoric 

 acid, etc. The amount excreted is increased by a protein diet, 

 since the phosphates of the nucleoproteins, lecithin, the phospho- 

 proteins, etc., are the main source of urinary phosphates. Some 

 inorganic phosphates also occur in the food as such. The 

 amount in the urine also is influenced by the fact that phos- 

 phates are excreted in the feces. This is due partly to failure to 

 absorb them, but also to the fact that phosphates are excreted 

 into the intestine and eliminated in the feces chiefly as calcium 

 phosphate. On an average, about 50-65% of the total phos- 

 phorus is excreted in the urine, the remainder in the feces. Con- 

 stipation causes increase in urine phosphorus, and decrease in 

 that in the feces. Diarrhea has the opposite effect. The phos- 

 phates of the urine are sometimes differentiated into alkali phos- 

 phates, alkaline earth phosphates, and organically combined 

 phosphates. 



In pathological conditions the phosphorus excretion is in- 

 creased when there is increased destruction of nuclear material 

 as in leucemia. Also in starvation the bone tissue is gradually 

 drawn upon for fuel, and increased phosphate elimination re- 

 sults. The parathyroid glands also appear to be connected in 

 some way, as yet not understood, with phosphate excretion. 



Sulphates. Sulphur occurs in the urine in various forms. 

 Three classes usually are recognized, inorganic sulphates, 

 ethereal sulphates and unoxidized or "neutral" sulphur. The 

 total amount of sulphur excreted per day is variable, but usually 

 is somewhat less than a gram. The chief source of urinary sul- 

 phate is the sulhpur of the protein molecule. Most of this is 

 oxidized in the body, so that 75-80% of the total sulphur is pres- 

 ent as inorganic sulphate. The remainder is made up of organi- 

 cally bound sulphate, and of a mixture of traces of several com- 



