34 2 PHYSIOLOGICAL CHEMISTRY. 



UNKNOWN SUBSTANCES. 



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 precipitate 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 investigators claim that a positive reaction indicates an ab- 

 normal decomposition of protein material, whereas others assume 

 it to be due to an increased excretion of alloxyproteic acid, oxy- 

 proteic acid or uroferric acid. 



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

 orders, which is of value diagnostically only when taken in connec- 

 tion 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 car- 

 cinoma, chronic rheumatism, diphtheria, erysipelas, pleurisy, pneu- 

 monia, scarlet fever, syphilis, typhus, etc. The administration of 

 alcohol, chrysarobin, creosote, cresol, dionin, guaiacol, heroin, mor- 

 phine, 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 + HC1 = HN0 2 + NaCl. 



NH 2 N 



/ / \ 



(6) C 6 H 4 + HN0 2 = C 6 H 4 N + 2H 2 0. 



\ \ / 



HS0 3 S0 3 



Sulphanilic acid. Diazo-benzenesulphonic acid. 



1 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. 



(&) 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 proportion i : 50 when required. Green asserts that greater delicacy is se- 

 cured by mixing the solutions in the proportion i : 100. The sodium nitrite de- 

 teriorates upon standing and becomes unfit for use in the course of a few weeks. 



