PREFORMED PIGMENTS OF NORMAL URINE. 619 



portion of the substance we are now to describe, but they were mixed 

 with urobilin and with decomposition products. 



To A. E. Garrod l we owe a process for the extraction of the essential 

 yellow colouring matter, which is beyond reproach in its avoidance of 

 destructive reagents. It yields a product entitled to be considered, with 

 a large degree of probability, as a chemical individual. 



Following Garrod, we shall describe this pigment under the name of 

 uroclirome a name eminently fitted for a substance which is the prime 

 cause of the familiar colour of urine, but in the use of which we must 

 avoid historical confusion. 



Between the uro chrome of Garrod and that described thirty years 

 earlier there is the difference between presumptive chemical individual- 

 ity and almost certain admixture. It should be stated, however, that 

 Thudichum still holds the pigment described by him to be a definite 

 substance, and has recently investigated certain of its reactions, which he 

 believes indicate for it the combined characters of an alcohol and a base. 



Separation of urochrome (Garrod). The urine is saturated with crystals 

 of ammonium sulphate, and, after standing, is filtered (vide infra, " Separation of 

 Urobilin"). The filtrate, which is still almost as highly coloured as the original 

 urine, is shaken with alcohol. The latter solvent separates rapidly from the 

 saline mixture, and is seen to withdraw a large proportion of the colouring 

 matter. Repeated extraction removes practically all. The alcoholic solution 

 is diluted with a large bulk of water, and the mixture again saturated with 

 ammonium sulphate \ by this procedure the alcohol is again made to separate 

 from the water, carrying the pigment with it, and a satisfactory washing of 

 the original extract is secured. This second alcoholic solution is now made 

 just alkaline with ammonia, and evaporated to dryness ; the residue is 

 extracted once or twice with acetic ether, which removes certain impurities, 

 and is again dissolved in strong alcohol. Somewhat prolonged digestion is 

 necessary at this stage, as the solubility in alcohol is decreased when the 

 pigment has once been taken to dryness. Finally, the alcohol is concentrated 

 till it has a deep orange colour, and is poured into at least an equal volume of 

 ether, when an amorphous brown precipitate falls, consisting of the greater 

 portion of the pigment present, in almost pure condition. The precipitate 

 may be filtered off, dried on the paper, and washed with a little chloroform 

 and absolute alcohol. 2 



Properties. The substance so prepared is a hygroscopic, brown, 

 amorphous substance, easily soluble in water, much less soluble in 

 alcohol ; only slightly soluble in acetic ether, amyl alcohol, or acetone ; 

 and insoluble in chloroform, ether, and benzene. Its solutions show no 

 definite spectroscopic absorption-bands, even after the addition of acids. 

 Zinc chloride and ammonia produce no fluorescence. Alkalies give the 

 solution a brownish tint, acids a reddish brown. The pigment forms 

 insoluble compounds with the heavy metals, and is precipitated by 

 phosphotungstic and phosphomolybdic acids. With strong nitric acid 

 it undergoes a colour change resembling the xantho-proteic reaction. 



Urochrome we have seen to be a pigment which can be removed 

 from the urine without the use of strong reagents, and in the removal 

 of which the fluid loses nearly all its colour. At the same time, its aqueous 



1 Proc. Roy. Soc. London, 1894, vol. Iv. p. 394. 



2 See also Kramm, Deutsche med. Wclmschr., Leipzig, 1896, Bd. xxii. S. 25 arid 42. This 

 author separates the pigment by an entirely different method. He confirms Garrod's 

 original account of its properties. 



