A contribution to the study of the yellow colouring matter of the urine / by Archibald E Garrod, M.A., M.D. (Oxon), F.R.C.P.

  • Archibald Garrod
Date:
[1894?]
Catalogue details

Licence: Public Domain Mark

Credit: A contribution to the study of the yellow colouring matter of the urine / by Archibald E Garrod, M.A., M.D. (Oxon), F.R.C.P. Source: Wellcome Collection.

    10/18 page 401
    distilled water has been carried out, the filter paper will merely be coaced with an amorphous brown film, and there will be no appreciable deposit of crystalline impurities. The filtrate of ether and alcohol will have a yellow colour, as it is able to hold a considerable quantity of pigment in solution. The filter paper, to which the pigment clings tenaciously, is allowed to dry and is then soaked for a time in chloroform which remains un¬ tinted, and afterwards in absolute alcohol. The alcohol becomes coloured by the pigment, but does not dissolve it nearly so readily as before. The paper is then allowed to soak for an hour or so in distilled water, by which means a clear orange-coloured or yellow aqueous solution is obtained, which should yield no indigo reaction, and which contains the pigment in a condition approaching to purity, although it is certainly not entirely pure. I believe, however, that no pigment other than the yellow one is present, and the absence of those which show absorption bands can be definitely established. When it is treated with sodium hypobromite, a little nitrogen is evolved, the freedom from urea being in proportion to the amount of washing or soaking in alcohol that the brown precipitate has received. If only slightly washed, 1 c.c. of a concentrated solution tested by means of Southall’s apparatus, may give off nitrogen equivalent to as much as 0'003 gram of urea, but if the washing has been more thorough, the amount evolved is too small to be measured. Seeing how soluble urea is in alcohol and in water, whilst it is almost insoluble in ether, it is only to be expected that this substance should constitute the chief impurity in the specimens. When the residue obtained by evaporation of the aqueous solution is burnt on a platinum dish, it yields a very bulky mass of carbon, and ultimately a trace of colourless ash, varying in quantity, which is readily soluble in water, contains no appreciable amount of carbonate, and apparently consists of sodium phosphate.* * May 9th, 1894.—It has been suggested that the yellow pigment may contain some, at least, of the iron which is present in urine, but although I cannot state that the product obtained by the above process is absolutely free from iron, the amount of that element contained in it is, at most, exceedingly minute. After the combustion of such small quantities as 1 or 2 cgrm. of the dry pigment, the sulphocyanide test gave negative results, provided that iron-free reagents, and filter-papers which had been extracted with hydrochloric acid, wrere employed in the process ; but with as much as 6 cgrm. a just perceptible tint was obtained, in no way comparable with that yielded by a fiftieth part of that weight of haemo¬ globin. I am, therefore, inclined to look upon this minute trace of iron as an accidental impurity, probably derived from the urine, rather than as a constituent of the yellow pigment. When heated with potassium hydrate the yellow pigment was found to give off ammonia freely.
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