URINE AND ITS CONSTITUENTS. 737 



Legal's test for acetone. To 25 c.c. of urine add an equal volume of a strong, 

 freshly-made solution of sodium nitroprusside, and then a few drops of sodium 

 hydroxide solution. In the presence of acetone a red color develops, which, on 

 addition of an excess of acetic acid, becomes darker red. (Compare WeyPs 

 reaction for creatinine.) 



Acetone may also be recognized in the following manner : 500 c.c. of urine 

 are acidified with a few drops of hydrochloric acid and distilled. To the dis- 

 tillate a few drops of iodine solution (1 iodine, 2 potassium iodide, 100 water) 

 and of potassium hydroxide are added. If acetone is present, a characteristic 

 yellowish- white precipitate of iodoform is formed. 



Diacetic acid is recognized by adding to the urine drop by drop a 

 fairly strong solution of ferric chloride, filtering off any precipitate 

 of phosphate, and adding more ferric chloride, when in the presence 

 of diacetic acid a deep-red color is produced, which disappears on 

 boiling. The test should also be made with an ethereal extract, ob- 

 tained by shaking urine previously acidified with sulphuric acid with 

 ether ; the ferric chloride solution, on being agitated with the ethereal 

 extract, becomes red. (As salicylic acid and a number of other sub- 

 stances give a red or violet color with ferric chloride, care must be 

 taken not to confound diacetic acid with these substances.) 



The detection of /3-oxy-butyric acid is difficult, and is rarely done 

 in clinical work. Its presence is probable when urine, after being 

 fermented, still contains a tavorotatory body. 



Bile may be present in the urine in any case of jaundice. 



Detection of bile-pigment. The presence of bile in urine is gen- 

 erally indicated by a decided color, which varies from a deep brown- 

 ish-red to a dark brown ; the foam of such urine (produced by shak- 

 ing) has a distinct yellow color, and a piece of filtering-paper or a 

 piece of linen dipped into the urine assumes a yellow color, which 

 does not disappear on drying. 



The further detection of bile depends upon the reactions of the 

 biliary coloring-matters or biliary acids. 



Tests for bile. 



1. Gmelin's test for biliary coloring-matters has been considered, 

 and may be applied to urine either by allowing a small quantity 

 of nitric acid, containing some nitrous acid, to flow down the sides 

 of a test-tube (containing the urine) in such a manner that the two 

 fluids do not mix, or by placing upon a porcelain plate a few drops 

 of the urine, near it a few drops of nitric acid, to which one drop of 

 sulphuric acid has been added, and allowing the two liquids to ap- 

 proach gradually. In both cases (if bile-pigment is present) a play of 



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