1867.] Esctractive Matters of Urine.~~Vd.Yi I. 



healthy urine to one-third or one-fourth of its vohime, adding a Httle nitric 

 acid, allowing it to stand for a day, during which time the colour of the 

 liquid changed from yellowish brown to dark red, and then mixing with a 

 solution of urate of potash. A precipitate was thereby formed of uric acid, 

 having the same red colour as the natural red deposits, from which the red 

 colouring-matter could be extracted by means of alcohol. Recent observers 

 have given names to this colouring-matter, such ^siwoerythrine imdi puiyu- 

 7*m(?, without, however, adding anything of importance to our knowledge of its 

 properties. The method adopted by them for its preparation is essentially 

 the same as that first suggested by the earlier chemists. The deposits 

 containing it are washed wdth water, and then digested with warm absolute 

 alcohol, which takes up the colouring-matter and, after filtration and eva- 

 poration at a temperature not exceeding 50°C., leaves it in the form of a 

 red amorphous residue. It cannot be obtained by evaporating the urine 

 containing it ; but on dissolving white and pure urate of ammonia in urine 

 (which by its pink or purple colour indicates the presence of purpurine), the 

 salt is precipitated, on cooling, deeply coloured, and yields the colouring- 

 matter on being treated in the way just described. It is not improbable 

 that this purpurine and the blue colouring-matter just referred to may 

 stand in some relation to one another. An observation made by iVngelini * 

 seems to favour this view. This chemist, being desirous of examining the 

 pink deposit which w^as being formed in his own urine during an attack of 

 fever, had it collected and laid aside ; but being unable, from the state of 

 his health, to examine it at once, it remained for some days exposed to the 

 atmosphere, and during this time the pink colour changed in many places 

 into blue. On leaving it to stand for some time longer, the blue tint did 

 not spread further, but the spots became darker in colour. 



Instances of black urine are even of rarer occurrence than those of urine 

 coloured blue. Indeed in many cases the black colour seems to have been 

 due to red or purple pigments, which communicated to the urine so deep 

 a tint as to make it appear black. Dulk, for instance, obtained from a 

 black urine a substance of the same colour containing iron, which Berzeliusf 

 with some reason suspected to be merely hematine. In the case described 

 by Marcet t, the urine appears to have been purple, or purplish-brown in 

 the first instance, and to have become black on standing. It contained no 

 red blood-globules and no trace of iron, and yielded no coloured deposit on 

 standing for a length of time, the colouring-matter being kept in solution 

 by the alkali, which was always present in excess. This colouring-matter 

 was examined by Prout, who gave it the name of melanic acid. It was 

 precipitated from the urine by means of acids in black flocks, which w^ere 

 found to be nearly insoluble in water and alcohol, but readily soluble in 

 caustic and carbonated alkalies, the solutions being of a very dark colour. 



^ Giorn. di Fisica. Dec. II. t. viii. (1825). 

 t Jahresbcriclit, 20ter Jahrg., S. 570. 

 X Medico-Cliirurg. Transactions, 1822. 



