//. A.)/. 1 TO PORPHYRIN. 625 
water. The solutions have a rich orange colour; only when very dilute 
and quite free from impurity do they exhibit a pink tint. All solutions 
uf the pigment are decolorised on exposure to light, even to subdued 
daylight. < hi the other hand, light has little effect upon the solid 
pigment, and none at all upon pink urate sediments. 
"When solid utderythrin is treated with solutions of the caustic 
alkalies, a remarkable green coloration is produced (Thudichum). (neen 
derivatives from animal pigments are so uncommon that the reaction is 
highly characteristic It can be well seen when a little pink urate 
deposit is collected upon a filter, dried, and then touched with a drop of 
sodium-hydrate solution. If a solution of the pigment be treated with the 
same reagent, a rapid play of colours may frequently be seen, from pink, 
through purple and blue, to grass-green. With acids, colour-reactions 
also occur, but they are somewhat less certain, being dependent upon 
exact conditions of experiment. If to a solution of the pigment 
sulphuric acid be added, the deep orange colour changes to a brilliant 
carmine. Hydrochloric acid produces a rose-pink, phosphoric acid a 
salmon-pink. 
Examined spectroscopically, a solution of uroerythrin, at a suitable 
degree of dilution, shows two somewhat ill-defined absorption-bands 
united by a shading of less intensity (Macmunn). The more red-ward of 
these is seen in the green between the lines D and E, and nearer the 
latter; the other closely agrees in position with the ordinary urobilin 
band at E (Eig. 57, Spectum 7). Pink ru'ate sediments and the carmine 
derivative produced by sulphuric acid agree in giving a single banded 
spectrum, namely, a broad band extending from the D line towards violet. 
(d) Hsematoporphyrin. — In 1881, Xeusser 1 and Macmunn 2 observed 
the occurrence in urine of pigments closely related to hffimatoporphyrin. 
During the following decade the work of le Xobel, Stockvis, Salkowski, 
Hammarsten, Copeman, and others extended this discovery, and it 
became established that hsematoporphyrin itself is a constituent of 
certain pathological urines. In 1892, A. E. Garrod 3 showed that it 
is also to be found in normal urine. 
In health the pigment is excreted in very small amount, and can 
scarcely be said to function as an active colouring matter of the urine : 
but it is of the highest interest to recognise that this iron-free deriva- 
tive of hrematin, which in the laboratory is only to be obtained by the 
use of strong reagents, is a normal physiological product. In patho- 
logical conditions, and especially after the use of certain drugs, it is 
present in greatly increased amount. 
Isolation from normal urine. — The method recommended by Garrod de- 
pends upon the fact that the pigment is carried down by the precipitate of 
phosphates produced on the addition of caustic alkali to the urine. After 
special treatment of this precipitate, the pigment may be obtained in chloroform 
solution. The chloroform is evaporated, and the residue washed with neutral 
alcohol and dissolved in acidified alcohol, when a solution is obtained of pure 
pink colour, comparable with solutions of the purest specimens of the pigment 
obtained from blood, and showing the spectrum of acid hsematoporphyrin with 
distinctness. 
1 Sitzungsb. d. J:. Akad. </. Jl'lsscnsch., Wien, 1881, Bd. lxxxiv. S. 536. 
2 Proc. Roy. Soc. London, vol. xxxi. p. 206. 
3 Joum. Physiol., Cambridge and London, 1S92, vol. xiii. p. 59S ; ibid., 1894, vol. xvii. 
p. 349. 
VOL. I. — 40 
