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Gold is precipitated from its solvent by ether, but the oxide is instantly re-dissolved by the ether, and forms an etherial solution of gold.
Obs. The etherial solution of gold may be applied to the gilding of steel scissors, lancets, aud other instruments, which it protects from rust, at a very small expense.
Exp. Into a given quantity of nitro-muriatic solution of gold pour twice as much sulphuric ether, shake then) together, and let the vessel stand for two or three minutes; then pour off into another vessel about ope third of the mixture. This will be an etherial solution of gold. To gild with it, make a polished steel instrument perfectly clean, and dip it into the solution, then plunge it into water, to wash off any acid there might be in the ether. The instrument will be covered with a coat of gold which may be burnished.
194. Platina is a white metal resembling silver in colour. It is the heaviest of all known substances, its specific gravity when hammered being 23.
Obs. Platina comes chiefly from Santa Fe in South America, and consists of small grains or scales, of a colour somewhat lighter than iron, and extremely heavy. In this state it is adulterated by several other metals, and requires to be purified before it is malleable.
195. Pure platina is extremely difficult of fusion, but when exposed to a white heat it softens so as to be welded like iron.
Obs. Platina may bo melted by exposing it in small quantities to Hare's blowpipe, charged with oxygen and hydrogen
gases.
196. Platina is not oxidated by exposure to air, or to the continued heat of a furnace ; neither is it acted upon by the most concentrated simple acids.
Obs. The proper solvent of this metal is aqua regia, composed of one part of the nitric, and three of the muriatic acid. The colour of the fluid becomes first yellow, and as the solution goes on, it becomes deep reddish brown. This solution is very corrosive and tinges the skin of a blackish brown colour
197. Platina combines with most of the other metals by fusion, and forms alloys possessing various properties.
Illua. It renders silver more hard, but its colour more dull.
Copper, when alloyed with from l-6th to l-25th part of it, is rendered of a golden colour; is much less apt to rust, and receives a finer polish.
With iron it is said to form a compound much esteemed by the Spaniards, for the purpose of making gun barrels, which are stronger, and much less apt to rust than iron alone.
198. Platina is so ductile that it may be drawn into wire not exceeding the three thousandth part of an inch in diameter.
199. From its infusibility and the difficulty with which it is oxidated, this metal is of great value in the arts, and for making various chemical and philosophical instruments.
0A*. Platina is a remarkably slow conductor of caloric. Thus when equal pieces of silver and platina are coated with wax, and heated at one end, the wax on the silver will be melted 3J inches in the same time that only one inch is melted on the platina. This property of conducting heat slowly has been applied to a very curious, and useful purpose. If a coil of platina wire surrounding a cotton wick immersed in alcohol, be made red hot, the evaporation and combustion of the alcohol keeps it in this state. Thus we have a coil of wire constantly red hot without flame, and from which, by means of a match, a light may be obtained at any moment.