Potash, soda, and ammonia dissolve haema tosin8 with facility, and it is precipitated from such solution by the addition of an acid. The acetic acid acts thus, but re-dissolves the pre cipitate if added in excess, as it would albu men or fibrine.
Tannin precipitates haematosine from solu tion in alkalies.
Tiedemann and Gmelin have observed that boiling alcohol will dissolve htemarosine; this is also the case to a considerable extent with its combinations with several of the acids which precipitate it. When hwinatosine is incinerated and decarbonized, it yields an ash amounting to 1.3 per cent. of its weight : this, according to Berzelins, is composed of the following sub stances:— Carbonate of soda, with traces of phosphate 0.3 Phosphate of lime 0.1 Caustic lime , 0.2 Subphosphate of iron ..... 0.1 Sesqui-oxide of iron 0.5 Carbonic acid and loss 0.1 1.3 The ultimate analysis of hiematosine ap proaches very nearly to that of fibrine. Mi chiielis declares to have found a difference of ultimate constitution between the colouring matter of arterial and venous blood : his ana lyses are as follows : Arterial. Venous.
Nitrogen 17.253 17.392 Carbon 51.382 53.231 Hydrogen 8.354 7.711 Oxygen 23.011 21.666 It will be observed, on examining these ana lyses, that the difference of constitution is so small that we may reasonably conclude it has been produced by a difference in manipulation or some other extraneous cause capable of modifying the result: indeed, ultimate ana lyses of identical substances have, when in the hands of different chemists, often yielded re sults far more discrepant than these, and that too when each operator stood high as an ana lyst. Berzelius, in remarking on these expe riments, observes that it is impossible for the chemist to fix the state of blood whether arterial or venous; for it will lose its condition with respect to the colouring matter long before the chemist can procure its hwmatosine for analysis. Thus the venous clot becomes of a bright red colour when exposed to air, and arterial blood soon loses its vermilion clue. A great con trariety of opinion exists as to the cause of the red colour of hwmatosine, some chemists sup posing that the iron contained in it takes an active part in its coloration, while others maintain that though iron is present it cannot be considered as the cause of colour. \Vin t& imagined lie had discovered the secret when he formed sulphocyanic acid (blut siiure) by carbonizing blood with carbonate of potash and precipitated salt of iron with the lixivium an experiment quoted by Treviranus ; but we are unable to detect the sulphocyanic acid in blood, so this formation of a ferruginous co louring matter must not be considered as in any way assisting in the inquiry, although it simulates the tint of blood most completely. Fourcroy asserted that subphosphate of iron was capable of imparting a red colour to serum, which is not the case, and went so far as to declare that the colourless globules of the chyle contained neutral phosphate of iron, which, when mixed with the blood, was de composed by the alkali present into a sub phosphate, which on reaching the lungs be came a per-salt and imparted colour to the fluid. This idea is quite hypothetical, and in
discordance with facts as observed by other chemists.
Engelhart's experiments on hmmatosine tend to spew that iron is in some way influential in producing the red colour of the blood. lle showed that, though albumen and fibrine yielded no iron on incineration, the metal ex isted in considerable quantity in hwmatosine. Ile found that a solution of red particles im pregnated with sulphuretted hydrogen became of a violet colour and then passed to a green, it balg impossible to restore the original red tint. Chlorine when passed through the solution bleached it, having previously produced a green colour; when decolorization was com plete, white flocculi were observed to fall, which on being examined yielded no appre ciable ash, while the clear solution gave evi dence of iron by the usual reagents. The white flocculi were supposed by Engelhart to be the colouring matter changed to white by the abstraction of its iron. It is evident that even if the colour of the blood were owing to some peculiar animal matter and not to iron, we should still expect decolorization by chlo rine; but yet the change of colour from red to green which that re-agent produces previous to decolorizing the solution, renders it probable that its action is on iron in some form of com bination as yet unknown. Rose has shown that many organic matters interfere with the action of the tests for iron when present in solution with that metal, and quotes this to account for the failures in procuring the re actions of iron from the blood in a fluid state. Some experiments of Berzelius, however, have proved that the artificial combinations Of iron with albumen which Rose formed, can be pre cipitated by ferrocyanate of potassa if they are previously treated with acetic acid : as this does not happen with blood, it is very pro perly contended that Rose's experiments are not to be looked upon as an explanation of the difficulty. In a paper published by Alr. Brande in the Philosophical Transactions for 1812, that gentleman proposes to consider hwmatosine as an animal dye, which like co chineal is capable of uniting with metallic oxides ; thus the oxides of mercury and tin are active precipitants of this colouring matter, and woollen clothes previously impregnated with a solution of bichloride of mercury have been permanently dyed by steeping them in a solution of liwmatosine. The question as to whether or not iron be really necessary to the existence of the red colour of the blood can not be considered as determined, and it is difficult to imagine any line of experimenting which could afford results sufficiently satis factory to settle the point. Mr. Brande's ex periments, by which he concluded that liwma tosine contained iron in no greater proportion than fibrine or albumen, would have placed the matter beyond doubt if other chemists had confirmed his observations ; but the expe riments of Dr. Engelhart published in 1825, and which have received very general con firmation, show that ftbrine and albumen when pure contain no iron, and that the metal exists in considerable quantity in Incrnatosine.
(G. O. Ras.)