THE URINE 



465 



from the uranium nitrate employed in the titration. The urine is heated 

 to 80 C., and the phosphates are then precipitated by a standard 

 solution of uranium nitrate. A little powdered solid potassium 

 ferrocyanide may be added as indicator. This turns brown when the 

 end-point is reached. One c.c. of the standard solution equals 

 0-005 gramme of phosphoric acid. 



Normally, about 2 to 3 grammes of the phosphoric ion (P 2 O 5 ) 

 are excreted daily. This is chiefly derived from the phosphorus 

 compounds of the food, inorganic phosphates, and organic phosphorus 

 compounds, such as phospho-protein, nucleo-protein, and lecithin. 

 A considerable proportion of the phosphates is excreted by the large 

 bowel, particularly the earthy phosphates. The deposit of phosphates 

 which sometimes occurs in the urine of children is probably due to 

 an excessive amount of calcium in the urine arising from defective 

 excretion by the large intestine. 



Carbonates. These occur as the carbonate and bicarbonate, 

 particularly of sodium, after the ingestion of organic acids in vegetables 

 and fruits. A crystalline deposit of calcium carbonate may be found 

 (Fig. 225). On addition of acid, the urine effervesces 

 from the evolution of carbon dioxide. The urine of the 

 horse or cow is normally alkaline, and cloudy with 

 phosphates and carbonates. 



Abnormal Constituents of the Urine. The chief 

 abnormal constituents met with in urine are protein, 

 sugar, blood, and bile. 



Proteins. Various proteins may be passed in the 

 urine. In the condition known clinically as albuminuria 

 the serum albumin and serum globulin of the blood 

 pass through the kidneys into the urine. The former is 

 usually in larger amount. Such a urine always gives 

 an abundant froth on shaking. " Albumin " in the 

 urine is detected by the following tests, which must be 

 applied to clear urine i.e., filtered or centrifuged if 

 necessary: (1) The urine boiled after being faintly 

 acidified with acetic acid. Albuminous urine gives a 

 coagulum. (2) On the careful addition of nitric acid a 

 white ring (precipitate) appears at the junction of the 

 fluids. This ring does not disappear on heating. 



Other tests mentioned in the section on the proteins 

 (p. 46) may also be used. It must be remembered, 

 however, that normal urine contains a trace of protein, and the 

 tests employed should be such as will reveal only an increase beyond 

 the normal amount. 



For quantitative clinical purposes, a special form of test-tube 

 is used (Fig. 226). This tube is filled with clear urine up to the 

 mark U, and a mixture of picric and cit.ic acids up to the mark R. 

 If albumin be present, a whitish-yellow precipitate forms. On leaving 



30 



E S.BACH'S 

 ALBTJMINO 



METER. 



