140 OXYPROTEIC ACIDS 



Chemical Position of Urochrome. It is at present not 

 advisable to say more in reference to the chemical classi- 

 fication of urochrome, the urinary coloring matter which 

 is mainly responsible for the yellow color of normal urine, 

 than that we are dealing with one of the substances in- 

 cluded in the group of protein residual matter which 

 from its characteristics of solubility and precipitability 

 should be classed among the oxyproteic acids. There is a 

 contradiction in the matter of its sulphur content between 

 the statements of the above-named Polish authors, who found 

 the coloring material to contain sulphur, and the results ob- 

 tained in Hofmeister's laboratory. 57 The latter indicate 

 that the yellow material, which can be separated from the 

 urine by animal charcoal and can subsequently be freed from 

 the latter by glacial acetic acid (known as "wopyrryl" 

 because of the large proportion of pyrrol left when it is 

 subjected to dry distillation), does not contain any sulphur. 

 It may be thought that this contradiction may be explained 

 on the supposition that the urochrome, which has its sulphur 

 bound so loosely in the molecular structure that sulphuretted 

 hydrogen separates, even without heating, when it is acted 

 upon by alkali, 58 may likewise undergo cleavage in the 

 course of the above process of demonstration with loss of its 

 sulphur ; but this has not been proven. There may possibly 

 be a close relation between such a sulphur partition and the 

 peculiar reduction power of urochrome which can be directly 

 estimated by titration by separation of iodine from iodic 

 acid. 59 The suggestion that urochrome owes its coloring to 

 one of the cyclic groups of the protein molecule included in 

 some form in its structure (or a transformation product of 

 such a substance) is not improbable. There is not the least 

 foundation, however, for assuming a relation between 



07 H. Hohlweg, K. E. Salomonsen, S. Mancini (Lab. of Physiol. Chem., 

 Strassburg), Biochem. Zeitschr., 13, 199, 205, 208, 1908. 



88 S. Bondzynski, S. Dombrowski and K. Panek, Zeitschr. f . physiol. Chem., 

 46, 83, 1905; S. Dombrowski, ibid., 62, 358, 1909. 



69 J. Browinski and S. Dombrowski, Jour, de Physiol., 10, 819, 1908. 



