454 PHYSIOLOGICAL CHEMISTRY 



pulmonary tuberculosis. The presence of sugar, albumin or urobilin 

 in low concentration does not interfere with the test. The test often 

 runs parallel with the diazo reaction (see below.) The test is supposed 

 to be positive when the focus of the lung is so active or extensive as to 

 flood the blood with toxins or to break down the defensive forces of the 

 body. It is claimed, therefore, that this test will differentiate the 

 cases in which the tuberculosis is beyond help from the tuberculin 

 from those in which the body is liable to respond favorably to its 

 action. 1 Some investigators claim the test is not specific and that a 

 positive reaction will be obtained in many disorders other than 

 tuberculosis. 2 



UNKNOWN SUBSTANCES 



i. Ehrlich's Diazo Reaction. Place equal volumes of urine and Ehrlich's 

 diazobenzenesulphonic acid reagent 3 in a test-tube, mix thoroughly by shaking, 

 and quickly add ammonium hydroxide in excess. The test is positive if both the 

 fluid and the foam assume a red color. If the tube is allowed to stand a precipi- 

 tate forms, the upper portion of which exhibits a blue, green, greenish-black, or 

 violet color. Normal urine gives a brownish-yellow reaction with the above 

 manipulation. 



The exact nature of the substance or substances upon whose presence 

 in the urine this reaction depends is not well understood. Some in- 

 vestigators claim that a positive reaction indicates an abnormal de- 

 composition of protein material, whereas others assume it to be due 

 to an increased excretion of alloxyproteic acid, oxyproteic acid, or uro- 

 ferric acid. Weisz 4 claims that urochromogen is the principal urinary 

 substance which causes a positive diazo reaction. 



The reaction may be taken as a metabolic symptom of certain dis- 

 orders, which is of value diagnostically only when taken in connection 

 with the other symptoms. The reaction appears principally in the urine 

 in febrile disorders and in particular in the urine in typhoid fever, 

 tuberculosis, and measles. The reaction has also been obtained in the 

 urine in various other disorders such as carcinoma, chronic rheumatism, 



1 M. and A. Weisz: Wien. klin. Woch., 25, 1183, 1912. 



Dozzi: Gazetta d. Osp. e delle Clin., 34, 815, 1914. 



Burgess: Jour. Am. Med. Ass'n., 66, 82, 1916. 

 2 Tuliato: Gazetta d. Osp. e delle Clin., 35, 1914. 



Martelli and Pizzetti: Potictinico, 21, April i, 1914. 



3 Two separate solutions should be prepared and mixed in definite proportions when 

 needed for use: 



(a) Five grams of sodium nitrite dissolved in i liter of distilled water. 



(b) Five grams of sulphanilic acid and 50 c.c. of hydrochloric acid in i liter of distilled 

 water. 



Solutions a and b should be preserved in well-stoppered vessels and mixed in the propor- 

 tion i : 50 when required. Green asserts that greater delicacy is secured by mixing the 

 solutions in the proportion i :ioo. The sodium nitrite deteriorates upon standing and 

 becomes unfit for use in the course of a few weeks. 



4 Weisz: Munch, med. Woch., 58, 1348,1911. 



