THE INORGANIC CONSTITUENTS OF URINE. 85 



insoluble in water, readily soluble in acetic and carbonic acid, 

 and are precipitated by ammonia. 



(a.) To clear filtered urine add nitric acid, boil, and add 

 baric chloride, and boil again = a precipitate of baric sul- 

 phate. Filter, and to the cool nitrate 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. 



6. The Alkaline Phosphates are chiefly acid sodium phosphate, 

 with perhaps traces of potassium phosphate ; they are soluble in 

 water and not precipitated by alkalies, and never occur as 

 urinary deposits. The quantity is 2 to 4 grammes (30 to 60 grs.) 

 They are chiefly derived from the food, and perhaps a small 

 amount from the oxidation of the phosphorus of nerve tissues. 



(a.) To fresh, clear filtered urine, add ammonia, caustic 

 soda, or potash, and heat gently until the phosphates begin 

 to separate ; let it stand for some time = a white precipitate 

 of the earthy phosphates. Allow it to stand, and estimate 

 approximately the proportion of the deposit. [If a high- 

 coloured urine be used, the phosphates may go down coloured.] 



(b.) To urine add about half its volume of nitric acid, and 

 then add solution of ammonium molybdate and boil = a 

 canary-yellow precipitate of ammonium phospho-molybdate. 



N.B. The molybdate is apt to decompose on keeping. 



(c.) To urine add half its volume of ammonia, and allow 

 it to stand = a white precipitate of earthy phosphates. Filter 

 and test the filtrate as in 6 (b.) 



(d.) It gives the reaction for phosphates. This method 

 separates the alkaline from the earthy phosphates. 



(e.) To urine add half its volume of baryta mixture 

 [Lesson XVI., 2 (c.)] = a copious white precipitate. Filter 

 and test the filtrate as in 6 (c.) It gives no reaction for phos- 

 phoric acid, showing that all the phosphates are precipitated. 



