THE EHRLICH DIAZO KEACTION 337 



temperatures of 104° and 105° are very rarely accompanied by the 

 diazo reaction; also by the fact that Gerhardt found the diazo re- 

 action in half of his cases of afebrile typhoid. In nearly all cases 

 there is evidence of a marked intoxication of some sort bordering on 

 the typhoid state. There are some things which we know about 

 this substance. It is soluble in water and alcohol, insoluble in ether, 

 chloroform, benzol, xylol and carbon disulphide. Neither sugar of 

 lead, silver nitrate, nor platinic chloride precipitate the substance 

 from urine. Liquor plumbi subacetatis and milk of lime precipi- 

 tate most of it. It exerts no reducing action on alkaline copper 

 sulphate solution. In making the test it is best that the urine be as 

 fresh as possible. However, urine which has been evaporated to a 

 syrupy consistency will retain the capacity to give this reaction indefi- 

 nitely (Michaelis). After nine months, when dissolved in an equal 

 quantity of water, it gave the reaction very well (Clemens). In poly- 

 uria the reaction may disappear, but on concentration of the urine 

 the test becomes positive. Various materials, such as bilirubin, 

 urobilin, and carbol, interfere with the reaction somewhat, but can be 

 removed by sugar of lead or animal charcoal. Burghart states that 

 when preparations of tannic or gallic acid, or tincture of iodine (not 

 the salts of iodine), are taken internally they prevent this reaction 

 in patients who have previously shown for some time good diazo 

 tests. This statement, if confirmed, is a very important one, as these 

 preparations are often given in two of our most important diazo 

 diseases — tuberculosis and typhoid fever. The author believes that 

 these substances attack the diazo reagents and thus prevent the re- 

 action. I am unable to refute or confirm these statements. Clemens 

 declares that in the test-tube tannic acid precipitated or destroyed 

 the substance, which was not recovered by the use of hydrochloric 

 acid. 



In this article I shall record the results of a critical analysis of 

 the diazo tests made in the clinic of Dr. George Dock, University of 

 Michigan, from 1893 to 1900. It is a sequel to the report of Dr. 

 "Warthin published in 1893. The method of performing the test has 

 been the same as that used by him, and is practically the same as 



