URINE. 341 



It is claimed that melanuria is proof of the formation of a vis- 

 ceral melanotic growth. In many instances, without doubt, urines 

 rich in indican have been wrongly taken as diagnostic proof of 

 melanuria. The pigment melanin is sometimes mistaken for indigo 

 and melanogen for indican. It is comparatively easy to differentiate 

 between indigo and melanin through the solubility of the former in 

 chloroform. 



In rare cases melanin is found in urinary sediment in the form 

 of fine amorphous granules. 



EXPERIMENTS. 



1. Zeller's Test. To 50 c.c. of urine in a small beaker add an 

 equal volume of bromine water. In the presence of melanin a 

 yellow precipitate will form and will gradually darken in color, ulti- 

 mately becoming black. 



2. von Jaksch-Pollak Reaction. Add a few drops of ferric 

 chloride solution to 10 c.c. of urine in a test-tube and note the 

 formation of a gray color. Upon the further addition of the chlor- 

 ide a dark precipitate forms, consisting of phosphates and adhering 

 melanin. An excess of ferric chloride causes the precipitate to 

 dissolve. 



This is the most satisfactory test for the identification of melanin 

 in the urine. 



UROROSEIN. 



This is a pigment which is not present in normal urine but may 

 be detected in the urine of various diseases, such as pulmonary 

 tuberculosis, typhoid fever, nephritis and stomach disorders. Uro- 

 rosein, in common with various other pigments, does not occur pre- 

 formed in the urine, but is present in the form of a chromogen, 

 which is transformed into the pigment upon treatment with a min- 

 eral acid. 



EXPERIMENTS. 



1. Robin's Reaction. Acidify 10 c.c. of urine with about 15 

 drops of concentrated hydrochloric acid. Upon allowing the acidi- 

 fied urine to stand, a rose-red color will appear if urorosein is 

 present. 



2. Nencki and Sieber's Reaction. To 100 c.c. of urine in a 

 beaker add 10 c.c. of 25 per cent sulphuric acid. Allow the acidi- 

 fied urine to stand and note the appearance of a rose-red color. 

 The pigment may be separated by extraction with amyl alcohol. 



