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Mr. E. Schiinck on the Colouring 



[Jan. 11, 



The first class is again subdivided by the author into blue, purple or 

 red, and black or brown colouring-matters. The appearance of a blue 

 coiouring-matter in urine has been frequently observed, both in ancient 

 and modern times. By some it has been taken for indigo-blue, by others 

 for Prussian blue, while several chemists maintain that it consists of a pe- 

 culiar substance, to which the name of cyanourine has been applied. The 

 red colouring-matter is generally found in association with deposits of 

 urate of ammonia and urate of soda, to which it communicates a pink or 

 carmine tinge. Proust called it rosacic acid, while recent observers have 

 given it other names, such as uroerythrine and purpurine. Very little is 

 known regarding its true chemical nature. Prout, indeed, suggested that 

 it might be identical with purpurate of ammonia ; but he advanced no 

 good grounds in support of this view, and it was proved to be erroneous 

 by Berzelius. Instances of black urine are even of rarer occurrence than 

 those of urine coloured blue. Indeed in many cases the black colour 

 appears to have been due to red or purple pigments which communicated 

 to the urine so deep a tint as to make it appear black. The melanic acid 

 of Prout seems, however, to have been a peculiar substance, though closely 

 resembling, as remarked by Berzelius, the black pulverulent substance 

 which is formed by the action of concentrated acids on the extractive 

 matters of urine. 



The second class of urinary colouring-matters, comprising those which 

 are formed by artificial means and therefore do not preexist in the secre- 

 tion, may also be subdivided according to colour — those which have hitherto 

 been observed being either blue, red, or brown. The author concedes 

 to Pleller the merit of having first obtained from urine by artificial means 

 colouring-matters of a pure blue or red tint ; but the true nature of these 

 colouring-matters, as well as of the process by which they are formed, was 

 not understood by him. Subsequent researches have proved that the 

 uroglaucine and urorhodine of Heller are identical with the indigo-blue and 

 indigo-red obtained from vegetables. After mentioning the experiments 

 of Hassall, who observed the formation in morbid urine of a blue colour- 

 ing-matter which he showed to be indigo-blue, the author refers to his 

 own researches. In a paper published several years ago, he showed that 

 urine contained as a never-failing constituent a body closely resembling if 

 not identical with indican, the indigo-producing body of vegetables, and 

 that hence the formation of indigo-blue and indigo-red from urine might 

 easily be explained. This result has been confirmed by Carter and others. 

 The formation of brown colouring-matters by the action of acids on urine 

 was first observed by Proust, who obtained by this means a brown resinous 

 body and a black pulverulent substance. The same or similar bodies 

 were obtained by Scharling and Liebig, as well as the author, who gave a 

 general account of them in the memoir just referred to. The simultaneous 

 formation of glucose, or at least of a body having the same action on oxide 

 of copper as glucose, is a fact first observed by the author. From an exa- 



