112 PRACTICAL PHYSIOLOGY. [XVII. 



ever, exists in urine not only in combination with alkalies, as 

 indicated above, so-called "preformed sulphuric acid," but also 

 Avith organic radicles, phenol, skatol, and other aromatic substances 

 forming aromatic ether-sulpho-compounds, or " ethereal sulphates," 

 the "combined sulphuric acid." The latter form about J^th of 

 the total sulphates, and originate from putrefactive processes in the 

 intestine. The chief ethereal sulphates are phenol-sulphate ot 

 potassium and indoxyl-sulphate of potassium or indican (CgHgN) 

 KSO4. 



(a.) Test with a soluble salt of barium (the nitrate or chloride) 

 = white heavy precipitate of barium sulphate, insoluble in HNO3. 



(/>.) To separate the combined (ethereal) sulphuric acid, — Mix 

 50 cc. of urine with an equal bulk of " baryta mixture." Stir and 

 filter. This removes the ordinary sulphuric acid as sulphate of 

 barium. Add 10 cc. HCl, and keep in a water-bath at 100° C. for 

 an hour and then allow the ethereal or combined sulphates to 

 settle. 



5. The Phosphates consist of alkaline and earthy salts in the 

 proportion of 2 to i. The latter are insoluble in an alkahne 

 medium, and are precipitated when the urine becomes alkahne. 

 They are insoluble in water, but soluble in acids ; in urine they are 

 held in solution by free COg. The alkaline phosphates are very 

 soluble in water, and they never form urinary deposits. 



The composition of the phosphates in urine varies. In acid urine, the acid 

 salts NaH.P04 and Ca'H._.P04)2 are generally present. In neutral urine in 

 addition Na^HPOj, CaHP04, and MgHPOi- In alkaline urine there may be 

 also NasPOj Cas^POJj Mg3(P04}2. 



6. The Earthy Phosphates are phosphates of calcium (Ca3P04)2 

 (abundant) and magnesium (scanty) MgHPO^ + yHgO. Quantity 

 I to 1.5 grams (15 to 23 grs.). They are precipitated when the 

 urine is alkahne, although not in the form m which they occur in 

 the urine (Lesson XVI. 11). They are insoluble in water, 

 readily soluble in acetic and carbonic acid, and are precipitated by 

 ammonia. 



(«r/.) To clear filtered urine add nitric acid, boil, and add baric 

 chloride, and boil again = a precipitate of baric sulphate. Filter, 

 and to the cool filtrate add ammonia = a precipitate of baric 

 phosphate. 



Clinical Significance. — They are increased in osteomalacia and rickets, in 

 chronic rheumatoid arthritis, after prolonged mental fatigue, and by food and 

 drink, and diminished in renal diseases and phthisis. 



7. The Alkaline Phosphates are chiefly acid sodium phosphate 

 (NaHqPO^), with traces of acid potassium phosphate (KH0PO4); they 



