URINE 469 



UNKNOWN SUBSTANCES 



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

 diazobenzenesulphonic acid reagent 1 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,ror 

 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, o^xyproteic acid, or uro- 

 ferric acid. Weisz 2 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, 

 diphtheria, erysipelas, pleurisy, pneumonia, scarlet fever, syphilis, 

 typhus, etc. The administration of alcohol, chrysarobin, creosote, 

 cresol, dionin, guaiacol, heroin, morphine, naphthalene, opium, phenol, 

 tannic acid, etc., will also cause the urine to give a positive reaction. 



The following chemical reactions take place in this test: 



(a) NaN0 2 +HCl->HN0 2 +NaCl. 



NH 2 N 



/ /\ 



(b) C 6 H 4 + HN0 2 ->C 6 H 4 N+ 2 H 2 0. 



HSO 3 S0 3 



Sulphanilic acid Diazo-benzenesulphonic acid. 



1 Two separate solutions should be prepared Sid 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 1:100. The sodium nitrite deteriorates upon standing and 

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



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



