XVII.] THE INORGANIC CONSTITUENTS OF URINE. I 1 1 



The ratio of inorganic to organic constituents is I to 1.2-1.7. 

 The amount of salts excreted in twenty-four hours is 1 6 to 24 grams 

 (Jtofoz.). 



1. Water is derived from the food and drink, a small quantity 

 being formed in the body (normal quantity 1500 cc., or about 

 50 oz.). 



2. Chlorides are chiefly those of sodium (by far the most 

 abundant) with a little potassium and ammonium, derived chiefly 

 from the food, and amount to 10 to 13 grams (150 to 195 grains), 

 or a mean of 12 grams (180 grains). Sodic chloride crystallises 

 usually in cubes and octahedra. It sometimes forms a combina- 

 tion with urea, and then it crystallises in rhombic plates. 



(a.) Test with a few drops of AgN0 3 (i pt. to 8 distilled water) 

 = white, cheesy, or curdy precipitate in lumps insoluble in HN0 3 . 

 The phosphate of silver is also thrown down, but it is soluble in 

 HN0 3 . 



Estimation. A rough estimate may be formed of the amount 

 by allowing the precipitate to subside, and comparing its bulk 

 from day to day. 



Variations, increased in amount when the urine is secreted in excess, 

 although the Nad usually remains very constant (f per cent.) ; lessened in 

 febrile affections, and where a large amount of exudation has taken place, as 

 in acute pneumonia, when chlorides may be absent from the urine. The 

 reappearance of chlorides in the urine is a good symptom, and indicates an 

 improvement in the condition of the lung. N.B. The urine ought to be 

 tested daily for chlorides in cases of pneumonia. 



(b.) Evaporate a few drops of urine on a slide = octahedral or 

 rhombic crystals, a compound of NaCl and urea. 



(c.) Test urine from a case of pneumonia, and compare the 

 amount of the precipitate with that of a normal urine. 



3. Quantitative Estimation of Chlorides. (i.) Standard Silver Nitrate. 

 Dissolve 29.075 grams fused silver nitrate in 1000 cc. distilled water, i cc. 

 = 0.01 Nad. 



(2.) Saturated Solution of Neutral Potassic Chromate. 



(a.) Dilute 10 cc. of not too dark-coloured urine with 100 cc. water, and 

 place it in a beaker; add a few drops of (2). Allow the silver solution to drop 

 in, stirring all the time until a faint orange tint indicates that there is an end 

 of the reaction. Deduct i from the number of cc. of the silver solution 

 added. 



4. Sulphates are chiefly those of sodium and potassium. The 

 total quantity of sulphates (45 to 60 grs.) is 3 to 4 grams daily. 

 Only a small amount of them enters the body with the food, so that 

 they are chiefly formed from the metabolism of proteids in the 

 body. They have no clinical significance. Sulphuric acid, how- 



