154 Intdliffeiice and Miscellaneous Articles. 



ron and alumina, combined perhaps with a little water, are not to 

 be regarded as accidental impurities, rather than as essential parts 

 of the mixture. In this view the oxahevrite would be a variety of 

 apophyllite. — Ibid. p. I IH. 



ON THE IRON CONTAINED IN THE BLOOD. 



M. Englehart has shown that when an aqueous solution of the 

 colouring matter of the blood is treated with chlorine, it is decom- 

 posed ; a flocculent substance is deposited, which is insoluble in 

 water, and which, when separated by the filter, yields all the iron of 

 the colouring matter, by treating it with the commonly employed 

 re-agents. 



Mons. H. Rose has repeated and verified the experiments of En- 

 glehart. He found, however, that the iron precipitated by ammonia 

 contains a small quantity of phosphate of lime and subphosphate of 

 iron, and also that if excess of ammonia be added without sepa- 

 rating the flocculent matter, it is re-dissolved ; the liquid be- 

 comes of a deep brownish-red colour, and the iron does not pre- 

 cipitate. After a long time it is indeed true that flocculent matter 

 is deposited, but it contains scarcely any iron, almost the whole of 

 it I'emaining in the ammoniacal solution. It appears, therefore, that 

 the red colouring matter and the flocculent matter derived from 

 its decomposition by chlorine, possess the property of hindering 

 the precipitation of the iron by the alkalies; indeed, a considerable 

 quantity of solution of iron may be added to the colouring matter, 

 without its being precipitated by the alkalies. If the colouring 

 matter be destroyed by chlorine, and the insoluble matter be sepa- 

 rated, all the iron may be precipitated by re-agents ; but this is not 

 the case if the insoluble matter be left in it. There is however a 

 limit to these facts ; for when the iron is in too great proportion to 

 the colouring matter, the iron is then partly precipitated. 



iVI. Rose found that when the serum of human blood, or of the 

 ox or sheep, was mixed with a considerable quantity of solution of 

 iron, it presented the action of the usual re-agents upon the me- 

 tal. Ammonia and the other alkalies, although added in great ex- 

 cess, produced no precipate : they even re-dissolved that occasioned 

 by the addition of albumen to a solution of peroxide of iron ; and 

 neither hydrosulphuret of ammonia, nor tincture of galls, occasions 

 any precipitation in the solution. 



In general, peroxide of iron and other oxides are not preci- 

 pitable by alkalies, when an organic substance soluble in water is 

 added to the solutions, provided it be of such a nature as to be en- 

 tirely decomposable at a high temperature. On the contrary, when 

 an organic substance soluble in water is totally or mostly volatilized 

 without decomposition, it does not prevent the iron from being pre- 

 cipitated by the alkalies. The first effect is produced in a hot so- 

 lution of gelatine or starch, in gum arabic, linseed, mucilage, sugar, 

 sugar of starch and of diabetes ; the pectic, kinic, malic, citric, and 

 tartaric acids; in fact, this last acid has long been known to pro- 

 duce this effect. The contrary property was found in the following 



acids ; 



