Part 57 (1/2)
Q. _Why do STOVES and FIRE-IRONS become RUSTY, in rooms which are not OCCUPIED?_
A. Because the air is damp; and moist air _oxidizes_ (or rusts) iron and steel.
Q. _In what part of the year is it most difficult to keep STOVES and FIRE-IRONS BRIGHT?_
A. In _autumn and winter_; because the capacity of the air for holding water _being on the decrease_, its vapour is deposited on every-thing with which it comes in contact.
Q. _Why does GREASING iron prevent its becoming RUSTY?_
A. Because _grease_ prevents the humidity of air from coming in contact with the _surface of the iron_.
Q. _Why do not STOVES rust so frequently as POKERS and TONGS?_
A. Because stoves are generally _covered with plumbago_, or black lead.
Q. _What is plumbago, or black lead?_
A. A mixture of charcoal and iron filings.
A most excellent varnish to prevent rust is made of 1 pint of fat oil varnish, mixed with 5 pints of highly rectified spirits of turpentine, rubbed on the iron or steel with a piece of sponge. This varnish may be applied to bright stoves and even mathematical instruments, without injuring their delicate polish.
Q. _Why does ornamental STEEL (of a purple or LILAC colour) rust more readily than polished WHITE steel?_
A. Because the lilac tinge is produced by _partial oxidation_; and the process which forms rust has, therefore, _already_ commenced.
Q. _How can lilac STEEL be kept FREE from RUST?_
A. By keeping it in a very _dry place_; for then no additional oxygen will come in contact with it, to increase its amount of rust.
Q. _Do any OTHER metals (besides iron) combine rapidly with oxygen?_
A. Yes; copper, lead, mercury, and even silver to some extent.
Q. _Why does COPPER TARNISH?_
A. The tarnish of copper is caused by its _oxidation_; that is, the oxygen of the air combines with the surface of the copper, and instead of _rusting it_, covers it with a _dark tarnish_.
Q. _Why does LEAD lose its BRIGHTNESS, and become DULL and of a DARKER hue, by being exposed to the air?_
A. The vapour of the air combines with the lead, and _oxidizes its surface_; but instead of becoming _rusty_, the surface becomes _dull_, and of a _darker colour_.