RUS′MA. An arsenical iron pyrites, found in Galatia, which, when reduced to powder, and mixed with half its weight of quicklime, is used by the Turkish ladies to make their ‘PSILOTHRONS,’ or compounds to remove superfluous hair. See Depilatory.
RUST. Syn. Rubigo, L. The coating or film of oxide or carbonate which forms on the surface of several of the metals when exposed to a moist atmosphere; more particularly, that which forms on iron or steel (FERRI HYDRATE; HYDRATED SESQUIOXIDE OF IRON; FERRUGO, FERRI RUBIGO).
To prevent iron or steel goods rusting, it is merely necessary to preserve them from damp or moisture. In the shops, small articles in steel are, commonly, either varnished or enclosed in quick-lime finely pulverised; large articles are generally protected with a coating of plumbago, or of boiled oil, or some cheap varnish, applied to them, previously gently heated. Surgical instruments are frequently slightly smeared with a little strong mercurial ointment, with the same intention.
Spots of rust may be removed from the surface of polished iron or steel by rubbing them with a little tripoli or very fine emery made
into a paste with sweet oil; or, chemically, by a mixture of polisher’s putty-powder with a little oxalic acid, applied with water. When the last is employed, the articles should be afterwards well rinsed in pure water, then wiped dry, and finished off with a warm and dry rubber, in order to remove every trace of acid.
RUTHENIC ACID. Syn. Ruthenic anhydride (RuO3). This may be procured by heating any of the preceding oxides with potassic nitrate. Ruthenic acid is insoluble in water.
Ruthenic Sesquioxide (Ru2O3); occurs in the anhydrous form when the metal is ignited in a current of air. It is the most stable of the basic oxides of the metal. Alkalies fail to dissolve it. With acids it forms soluble salts of a yellow colour; when, to a solution of these, an alkali is added, a bulky blackish-brown precipitate of the hydrated oxide, having the composition Ru2O3,8H2O, is thrown down.
There are three chlorides of ruthenium:—RuCl2; RuCl3; and RuCl4.
RUTHEN′IUM. (Ru. = 104·2.) A metal discovered by Claus, associated with iridium, in the residue from crude platinum, which is insoluble in aqua regia. It forms small angular masses, with a metallic lustre; is very brittle and infusible; resists the action of acids, but readily oxidises when heated in the air. Sp. gr. 11 to 11·4.
In Fremy’s process for separating osmium from the residues of platinum ore, ruthenium occurs in a dioxide. By heating this dioxide in a current of oxygen, the metal may be obtained in the form of a powder of dark grey colour.