(Protoxide, Sesquioxide, and Sesquichloride of Iron. Salts of Iron:--viz., the Carbonate; Protosulphate; Persulphate; Phosphate; Pernitrate; Peracetate; Ammonio-citrate; Potassio-tartrate. Vinum Ferri. Chalybeate Waters.) Most of these substances are readily soluble in water. Steel wine contains a Tartrate. The insoluble oxides are doubtless dissolved by the aid of the acid of the stomach; and we find that both are most active when given in the form of hydrate, which is most easily soluble in such a menstruum. Thus Chalybeates are capable of being absorbed; and they no doubt are absorbed. They have been detected in the blood, and discovered in the secretions of urine and milk. Being in the blood, they act by an influence which they exert upon it; for they are wanting in all the characters which distinguish nerve-medicines. They are never sudden in their action, and the effect which they produce is lasting. Iron is found naturally in the blood; and the substance in which it is found is that which constitutes the colouring material of the red corpuscles. This is called Hæmatosin. It has been asserted by some that the red colour of Hæmatosin does not depend upon the iron which it contains. But however improbable this may be, it matters not here whether it be proved so or not; for it is sufficient that it is ascertained that Iron is essential to the chemical constitution of this red matter. Without Iron, Hæmatosin could not exist, any more than Albumen could continue to be Albumen, when deprived of nitrogen. According to the analysis of Mulder, Hæmatosin = C_{44}H_{22}O_{5}N_{3}Fe. It is a very peculiar body, and apparently an essential and most important constituent of the blood; for when it is deficient, as evidenced by the paleness of the tissues in Anæmia, the whole system suffers materially, and great and general debility is produced. The result of the administration of an Iron medicine is the restoration of this wanting colouring matter. For if the blood be analyzed before and after its employment, it is found to have undergone a remarkable change, most particularly in the quantity of Hæmatosin which it contains. A case in illustration of this is given by M. Simon, of Berlin. (_Anim. Chem._, vol. i. pp. 310, 313. _Syd. Society._) The solid constituents of the blood, in a case of Chlorosis, had increased, under the use of iron, from 128.5 to 193.5 in 1000 parts; the Globuline from 30 to 90; and the Hæmatosin from 1.48 to 4.59, in the same amount. It is probable that the increase in the Hæmatosin is the first change; that this then improves the condition of the blood corpuscles, increases their number, and through them betters the condition of the blood, and of the system generally.