AMOUNT, COMPOSITION, AND CHARACTER OF URINE 525 



tinual neutralization of those in solution may be obtained fairly accu- 

 rately by titrating the urine with % normal alkali in the presence of 

 neutral potassium oxalate, using phenolphthalein as an indicator (Folin). 

 The results may be expressed in acidity per cent in terms of c.c. N/10 

 NaOII required to neutralize 100 c.c. of urine. If the ammonia excretion 

 is added to the titration results, the total potential acidity is very closely 

 measured. 



The urine is more alkaline shortly after meals than at other times, 

 since acid is being excreted by the gastric glands. It is more acid on a 

 meat than on a vegetable diet, and is acid during starvation because 

 protein is then the chief metabolite. In disease there is no characteristic 

 variation, save that the urine is more generally acid, which may be ex- 

 plained by the fact that in serious illness the diet is restricted. When 

 the acidity is increased, the excretion of ammonia is usually greater, 

 since ammonium carbonate, the forerunner of urea, acts as an alkali and 

 neutralizes the acid radicles. This rise in ammonia, however, is not 

 always proportional to the acid radicles present, since the fixed alkali 

 derived from fruits and vegetables may be sufficient to neutralize the 

 acid formed. 



THE SOLID CONSTITUENTS 



For practical reasons we shall divide the constituents of the urine into 

 normal and abnormal. The former are present in the average urine in 

 amounts sufficient to be detected by ordinary means; the latter only 

 rarely appear in detectable quantities. In a person eating an ordinary 

 diet the most important organic and inorganic constituents of the urine 

 are as follows: 



TOTAL SOLIDS (40 TO 60 GRAMS) IN ONE LITER OF NORMAL URINE 

 ORGANIC CONSTITUENTS, "25-40 GM. INORGANIC CONSTITUENTS, 15-25 GM. 



Urea, 20-35 gm. Sodium chloride (NaCl), 8-15 gm. 



Creatinine, 1.011.5 gm. Phosphoric acid (P 2 O S ), 2.5-3.5 gm. 



Uric acid, 0.5-1.25 gm. - Sulphuric acid, (SO 3 ), 2-2.5 gm. 



Hippuric acid, 0.1-1.7 gm. Potassium (K,O), 2-3 gm. 



Other constituents (ethereal sulphates, Sodium (Na 2 O), 4-6 gm. 



oxalic acid, urinary pigments, etc.), Calcium (CaO), 0.1-0.3 gm. 



1.5-2.3 gm. Magnesium (MgO), 0.2-0.5. 



Ammonia (NH 3 ), 0.3-1.2 gm. 

 Iron (in pigme"nt), 0.001-0.010. 



(Compiled from Mosenthal's* figures.) 



These urinary salts are present in the blood, and are excreted only by 

 the kidney. An investigation of the mechanism of renal secretion must 

 therefore include a study of the relationship existing between the con- 

 centration of the urinary salts in the blood and in the urine. 



