68«

ELEMENTS OF MATERIA MEHIOA.

pvolution of hydrogen gas. The Solution contains the protosulphate of iron, andproduces, on the addition of canstic potash or soda, a greenish-white precipitate(the hydrated protoxide:) this precipitate, by exposure to the air, attracts oxy-gen, and is converted into the red or sesquioxide. Äuro-chloride of sodiumforms a purple precipitate with the protosalts of iron. By boiling the Solution ofthe protosulphate with a little nitric acid, we obtain a persulphate of iron, recog-nised by ferrocyanide of potassium, causing a blue precipitate; sulphoeyanic orrneconic acid, a red colour; gallic or tannic acid, or infusion of galls, a purpleor bluish black; and succioate, or benzoate of ammonia, a yellowish preci-pitate.

Physiological Effects. «. Of tiic MetalUc iron.—Iron is probably inert solong as it retains its metallic form, but it readily oxidizes in the alimentary canal,and thereby acquires medicinal power. As acids promote this chemical change,acid wines and fruits assist in rendering the metal active, while alkalis and theircarbonates have an opposite effect. The oxidizement of the iron is attendedwith the evolution of hydrogen gas, which gives rise to unpleasant eructations.If sulphur be taken along with iron, hydiosulphuric acid is developed. Like theferruginous preparations generally, the internal employment of iron canses black-ening of the stools. The nature of the effects produced by oxide ofiron formedin the alimentary canal will be best examined hereafter, under the head of ferru-ginous preparations. I may, however, remark here, that it is one of the few me-tals which by oxidizement is not rendered more or less poisonous.

ß. Of the Perrxiginous Compounds, a. a.. On Vegetables. —Most of the Com-pounds of iron do not appear to be hurtful to plants: at least this is the case withthe oxides. (De Candolle, Phys. Feg. 1837.) The sulphate, however, is in-iurious.

ß ß. On Jimmals. —The effects of the ferruginous Compounds on animals gene-rally ai;e similar to those on man. It is stated that in animals to whom iron hasbeen given for a considerable time, the spieen has been found smaller, harder,and denser—-an effect which is supposed to be owing to the increased contractilepower experienced by the veins of the abdomen. The liver is also said to havebeen affected in a similar manner, though in a somewhat slighter degree.

y y. On Man. —The local effects of the sulphate and Chloride of iron are thoseof irritants, and these preparations accordingly rank among poisons: but they arenot equal in power to the mercurial or cupreous salts. Most of the ferruginouspreparations are astringent; that is, they constringe the parts with which they arein contact, and thereby diminish secretions and check sanguineous discharges.Thus, when swallowed, they repress the secretions and exhalation of the gastro-intestinal membrane, and thereby render the alvine evacuattons more solid, andeven occasion costiveness. The sulphate and chloride of iron are the mostpowerful of the ferruginous astringents. Administered in large quantities, orwhen the alimentary canal is in an irritable condition, all the Compounds of ironare capable of exciting heat, weight, and uneasiness at the pracordia, nausea,and even vomiting, and sometimes purging.

The constitutional or remole effects 1 of the chalybeates are principally observedin the alteration induced in the actions of the vascular and muscular Systems, andare best seen in that State of the System denominated anasmia, or more properlyhypxmia, (See p. 44.) in which both the quantity and quality of the blood appeardefective.

We have a good Illustration of this State in chlorotic patients. The skia appears pale andalmost exsanjruineous, the cellular tissuc is oedematens, and, after death, the larger vessels aswell as the capijlaries are found to be impcrfectly supplied with blood. Patients with this con-dition of System are affected with great feebleness, loss of appetite, and palpitation ; and in

1 The best aecount of thß physiological effects ofiron is that published by Menghini {Da Fcrrearum parti-culanmprogressuadsanguinem) in the Comment. Jlcad. Bovtm, t. ii. pt, iii. p, 475. A notice of these is givenby Bayie in the Büliolkenc de Tkcravcutvinc, t. iv. Taris, 1837.