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.

    14/18 (page 405)
    faintly tinted. If acid is added they have a brown colour like that of crystals thrown down on the addition of acid to urine. The converse experiment to this was performed some years ago by Ord,# who showed that, on repeatedly redissolving and reprecipitating urinary uric acid, the crystals lost their colour, and, at the same time, tended to assume the tabular forms of those of pure uric acid. The above result lends strong support to the view that the pigment is isolated by the alcohol process in the form in which it actually exists in the fresh urine, and confirms the statement that it plays an important part in determining the forms which the crystals assumed Another fact which is demonstrated by this experiment is that the yellow pigment is one of those which colours the urinary crystals, although it does not stand alone in this respect. I do not, however, propose to enter further into this subject here, as I hope to deal with it at length in a separate paper, but I may mention that crystals of uric acid which are deposited from a solution of urobilin are colour¬ less and exhibit no modification of form, resembling, in every respect, those thrown down from pure aqueous solutions of urates. Summary and Conclusions. There cannot, I think, be any doubt that the substance isolated from the normal urine by the process here described is that to which its colour is almost entirely, if not entirely, due, and, since solutions of this substance do not fluoresce with zinc chloride and ammonia, show no absorption bands, and cannot be got to show a urobilin band by any process to which it was subjected, it follows that urobilin is not the chief colouring matte]1 of normal urine. Moreover, there is every reason to believe that the product obtained has not undergone any notable change in the process of extraction, although its solu¬ bility in various media appears to be somewhat impaired. The question whether the yellow colouring matter so obtained is a definite chemical entity is one to which it is very difficult to give a conclusive answer, chiefly on account of its physical properties. However, the uniform course of events observed on each of the many occasions on which the alcohol and ether process was carried out, strongly suggested that the product was a definite compound. This view also received support from its behaviour towards its solvents and its precipitation by ether, as well as by its effect upon uiic acid crystals, which is hardly what might be expected from a mixture of pigmentary substances. The only fact with which I am acquainted which appears to be opposed to this idea is the impossibility of completely decolorising its solutions by certain metallic precipitants, which throw down the * “ Tlie Influence of Colloids upon Crystalline Form and Cohesion,” 1879, p. 52.