112 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



meters of chloroform, mix repeatedly, avoiding shaking too 

 vigorously, separate the chloroform, and add to it a drop of 

 an alcoholic solution of zinc chloride; any turbidity is to be 

 cleared up by the addition of absolute alcohol: the chloro- 

 form becomes rose-red with a greenish fluorescence (E. Wir- 

 sing J ). 



5. Urine containing a considerable quantity of urobilin 

 gives the biuret reaction with caustic soda and copper sul- 

 phate solutions (confusion with albumoses and peptones). 



If the urobilin cannot be detected by the above methods 

 proceed as follows: 



1. Precipitate 200 cc. of urine completely with basic lead 

 acetate, filter, wash once with water, dry the precipitate at 

 room temperature, grind it in a mortar with alcohol and 5 g. 

 of oxalic acid, let stand twelve to twenty-four hours, and 

 filter (if absolute alcohol is used, the drying of the precipi- 

 tate may be dispensed with; it is then sufficient to drain it 

 thoroughly on filter-paper). Make a portion of the filtrate 

 alkaline with ammonia, filter from the ammonium oxalate 

 which separates, and add a drop of zinc chloride solution: 

 green fluorescence, absorption-band. Not infrequently, how- 

 ever, these reactions are indistinct. In this case, in order to 

 purify the rest of the alcoholic filtrate, shake it in a sepa- 

 rating-funnel with about 20 cc. of chloroform and enough 

 water so that the chloroform settles readily. Separate the 

 chloroform, filter it through a dry filter, and examine spec- 

 troscopically both before and after the addition of a drop of 

 an alcoholic solution of zinc chloride. 



The urine must not be allowed to stand too long before 

 it is examined, as the urobilin changes on standing into a 

 modification which lacks the most essential properties of 

 this pigment. This takes place even with urine containing 

 a considerable quantity of urobilin. 



1 Verhandl. d. Wiirzb. phys.-med. Gesellsch. N. F. 26, No. 3. 



