12S

PROOFS OF THE PROPERTIES OF IRON.

the same is the case when submitted to the action of sulphuratedhidrogen gas.

The Hack, or green oxid of iron, may also be obtained bykeeping iron filings for a length of time in water, at a tempera-ture of about ~0°. The oxid thus formed is a black powder,formerly known by the name of martial ethiops. It is likewiseobtained by making steam pass through a red-hot iron tube, orby burning iron in oxigen gas, or by decomposing a solution ofsulphate of iron by the addition of potash, and drying the preci-pitate expeditiously in a close vessel.

The red, or Iroivn oxid of iron, may also be formed by keepingiron filings red-hot in an open crucible, and agitating them con-stantly, till they are converted into a dark red powder, formerlycalled astringent satfron of mars.

It may also be produced by exposing a solution of iron in sul-phuric acid, for a long time to the atmosphere; or rather bypouring into it nitric, or oxigenated.muriatic acid.

Remark... We are indebted to Proust for an excellent memoirconcerning the combination of oxigen with iron; in which hehas illustrated in a very satisfactory manner, that metals are notcapable of indefinite degrees of oxidation, but only of a certainnumber, and that every particular oxid consists of a determinatequantity of the metal, and oxigen chemically combined.

The metal under consideration for instance, is not capable, aswas formerly supposed, of uniting with oxigen in all the inter-mediate degrees, between 0.2", and 0.48.

It can only combine with, precisely, 0.27 parts, or 0,48 parts,and icith.no other proportion; and therefore is only capable offorming the two oxids considered before.

To talk therefore of oxidating a metal indefinitely is not ac-curate, except it be intended to signify the combining of part ofit with oxigen, while the rest remains in its natural state.

If, therefore, iron be oxidated at all, it must he combined with0.2/ of oxigen; if it be oxidated more than this, it must becombined with 0.48 of oxigen.