OXIDE OF TIN.
Tin is a white metal, almost as white as silver, it is found chiefly in Cornwall. It is a light, soft metal, and, like lead, is easily melted; it is used chiefly for coating vessels of harder metal, such as iron and copper. It is used to mix with copper to produce bronze, bell metal, and gun metal, and with lead to produce pewter, which used to be so extensively used as table-ware before the manufacture of earthenware became general for that purpose. Tin does not easily tarnish or rust by exposure to the air, hence the use of tinned iron-plate. Tin, united with mercury, forms the silvering for looking-glasses. Tin is about seven-and-a-half times heavier than water.
ZINC.
SULPHURET OF ZINC.
Until the last quarter of a century, zinc was but little used, but of late it has taken the place for many useful purposes where lead was formerly used, principally owing to its cheapness and lightness. Zinc is a hard metal of a grayish colour, not easily bent but rather brittle, but when made nearly red hot, it is capable both of being rolled out into sheets and being beaten into form by the hammer. Zinc is about six-and-three-quarter times heavier than water. Like many other metals, zinc is volatile, that is to say, when heated to a certain extent it passes off into vapour, and there is no doubt, the reason that zinc was not known or used of old was that it was chiefly lost in “smelting,” or getting it from its ores. Zinc is now obtained by a sort of distillation; the ores are mixed with the flux, &c., in a large earthen crucible or pot, from which an iron tube passes into a vessel of water, the lid is securely fastened on, and as the heat is urged the zinc is driven off in vapour, passes down the tube and condenses in the water. The zinc of commerce is obtained chiefly from the ore known by the name of “calamine stone,” which is zinc in combination with oxygen and carbonic acid. A substance called “zinc white” has been lately introduced as a substitute for white lead, and would certainly supersede it, but the zinc is found to be deficient in “body,” which means, the power of covering anything over which it is laid-on in a thin layer, but as zinc white does not blacken in foul air, and white lead does, it has a great advantage, and it is to be hoped that some improvement in its manufacture may improve its “body.” Zinc is chiefly used for roofs, gutters, water-pipes, cisterns, and various vessels for holding water, as it does not rust so easily as iron. What is called “galvanised iron,” is iron dipped into melted Zinc in the same way that tin-plate is.