36 Researches into the Colouring -matter of Human Urine. 



7. Urobilin is the colouring matter of the bile of "the mouse. 



Before concluding this paper I should like to call attention to a 

 peculiarity which the band a of urobilin exhibits : in certain depths it 

 appears very broad, but in less depths it is seen that the portion of the 

 band nearest the violet has disappeared. In other words, the redward 

 part of the band is the most persistent and is the last to disappear on 

 dilution. Thus, taking the alcoholic solution of urobilin prepared by 

 the second process mentioned before, we find that when the extent of 

 the spectrum is 8 to 80 (or wave-length 694 — 432) this band reads 

 42 — 67 (or wave-length 517 — 453), but when the extent is 7 to 85 (or 

 wave-length 702 — 425) then the band reads 47 to 53 (or wave-length 

 502 — 485.) Urobilin, like heemaglobin and hgematin, appears to be a 

 very unstable body, which easily splits up on treatment with reagents 

 into decomposition products, each giving a peculiar spectrum. This 

 accounts for the differences observed in the spectra obtained by the 

 different methods I have described. 



EXPLANATION OF FIGURE (p. 27). 



1. Solar spectrum. 



2. Urobilin, prepared by the alcohol and sulphuric acid method, ethereal solution. 



3. The same treated with ammonia. 



4. Urobilin, prepared by the same method, dissolved in alcohol. 



5. Slight depth of the same. 



6. Solution, of which 4 is the spectrum, treated with ammonia. 



7. Urobilin, prepared as in 2 and 4, dissolved in chloroform. 



8. Shallow depth of the same. 



9. Solution, of which 7 is the spectrum, treated with ammonia. Solutions 3, 6, 



and 9, if examined in a shallow depth, show no band at F. 



10. Action of caustic soda on slight depth of solution in 2, 4, and 7. 



11. The pigment, prepared by the above method, dissolved in hydrochloric acid. 



12. Urobilin, prepared by the hydrochloric acid and alcohol method, dissolved in 



sulphuric acid ; at a shallower depth we get the band at F. 



13. Urobilin, prepared by the hydrochloric acid and alcohol method, in alcoholic 



solution. 



14. Shallow depth of same. 



] 5. Solution mapped in 13 treated with ammonia. 



16. Ethereal solution of urobilin, prepared as in 13 and treated with ammonia. 



17. Urobilin, prepared by the same method, dissolved in acetic acid. At less depth 



band at F is seen. 



18. Spectrum from residue, — got by treatment adopted for separation of urobilin, — 



from pale straw-coloured urine. 



