310 THE URINE. 



tion. The chloroform solution is then washed with water. On 

 final distillation the pigment remains as an amorphous reddish mate- 

 rial, which can be further purified by washing with ether, which takes 

 up contaminating red pigments. The substance is readily soluble 

 in alcohol, amyl alcohol, and chloroform, less readily so in water 

 and ether. 



Ehrlich's Reaction. When normal urine is treated with an 

 equal volume of a saturated solution of sulphanil.ic acid in 5 per 

 cent, hydrochloric acid to which a 0.5 per cent, solution of sodium 

 nitrite has been added in the proportion of 1 : 40, and the mixture 

 is then rendered strongly alkaline with ammonia, a more or less well- 

 marked orange color develops. Under pathological conditions, on 

 the other hand, and notably in typhoid fever, a red color results 

 which varies in intensity from a light carmin to a deep garnet-red. 

 This reaction is known as Ehrlich's diazo-reactioh, as it is dependent 

 upon the presence of a diazo- compound of the nature of diazo-ben- 

 zene-sulphonic acid, in the reagent. This results through an inter- 

 action between the sodium nitrite and the sulphanilic acid, as repre- 

 sented in the equations : 



(1) NaN0 2 -f HC1 := HN0 2 -f NaCl. 



/NH 3 /N~N 



(2) C 6 H/ | + HN0 2 = C 6 H/ | + 2H 2 



X S0 3 X S0 3 



Sulphanilic Diazo-benzene- 



acid. sulphonic acid. 



The action is supposedly referable to alloxy-proteinic acid. 



Under pathological conditions still other pigments may be found 

 in the urine. These comprise haemoglobin and its derivatives, 

 haematin, methaemoglobin, and haematoporphyrin ; further, also uro- 

 rubrohaematin and urofuscohaematiu, which are also undoubtedly 

 derived from haemoglobin, but which have thus far been found in 

 the urine on only one occasion ; further, the common pigments of the 

 bile ; and, finally, substances which belong to the class of the 

 so-called melanins. For a consideration of the various pathological 

 conditions under which the bodies may be met with, the reader is re- 

 ferred to special works on diagnosis. At this place I shall merely 

 describe the more common tests by which their presence can be 

 demonstrated. 



The Blood-pigments. If the microscopical examination of the 

 urine shows the presence of red blood-corpuscles in the sediment, 

 further chemical examination is, of course, unnecessary. Cases of 

 simple hsemoglobinuria, in contradistinction to hsematuria, may occur, 

 however, in which dissolution of the haemoglobin has taken place in 

 the circulation already, and in which blood-corpuscles do not appear 

 in the urine. In such an event the demonstration of blood-pig- 

 ment can be made only by chemical methods. Its presence, it is 



