476 PHYSIOLOGICAL CHEMISTRY. 



with about one-fourth of its volume of chloroform, which dissolves 

 the biliary matters. Some of this solution is dropped upon blotting 

 paper, and after evaporation a drop of red fuming nitric acid is 

 placed in the centre of the remaining stain, when concentric color rings 

 appear. The second portion of chloroform solution is evaporated 

 and the residue used for making the reactions as described above. 



Diazo-reaction. Some abnormal constituent (which has not yet 

 been isolated) is found in the urine of persons suffering from typhoid 

 fever. The presence of this unknown substance is indicated by a 

 very characteristic reaction with diazo-benzol-sulphonic acid, which 

 compound is produced by the action of nitrous acid on sulphanilic 

 acid. Two solutions are required : a. 2 grammes of sulphanilic acid 

 dissolved in a mixture of 50 c.c. of hydrochloric acid and 1000 c.c. 

 of water ; b. A 0.5 per cent, solution of sodium nitrite. To perform 

 the reaction 50 parts of a and 1 part of 6 are mixed, and equal 

 volumes of the reagent and of urine are mixed in a test-tube and 

 saturated with ammonia. In those cases in which the reaction is 

 positive the solution assumes a carmine-red color, which, on shaking, 

 must also be visible in the foam. If the test-tube is allowed to stand 

 twenty-four hours, a greenish precipitate is formed. Normal urine, 

 thus treated, shows a deep yellow or orange color ; the precipitated 

 phosphates as well as the foam are colorless. 



While the reaction is also found in some cases of measles, sepsis, scarlet 

 fever, etc., yet its constant and early presence in typhoid fever and its presence 

 in severe cases of pulmonary tuberculosis make the reaction of considerable 

 diagnostic and prognostic importance in these diseases. 



Acetone and diacetic acid. Both of these substances appear in 

 considerable quantities in the urine when there is marked destruction 

 of the protoplasm of the body ; they are more especially found in 

 cases of high fever, in some cases of cancer, and in severe forms of 

 diabetes. Large quantities of acetone appear in the urine during 

 disturbances of digestion and in intestinal diseases. 



Diacetic acid, CH 3 .COCH 2 .CO 2 H, is recognized by means of 

 Gerhard's ferric chloride reaction. A solution of ferric chloride 

 added to the urine produces a gray precipitate of ferric phosphate ; 

 upon the further addition of the iron solution a deep bordeaux color 

 appears. The foam produced on shaking the test-tube is reddish- 

 violet. On the addition of sulphuric acid the red color disappears. 

 Diacetic acid readily decomposes with the formation of acetone. 



