METAL′LICA. [L.] Preparations of the metals. One of the divisions of the Ph. L.
METAL′LIC TREES. See Vegetation (Metallic).
METAL′LO-CHROMES. A name given by Nobili to extremely thin films of peroxide of lead deposited by electrolytic action upon plates or polished steel, so as to produce an iridescent play of colours. The effect is often very beautiful.
MET′ALLOIDS. A name sometimes applied to the NON-METALLIC ELEMENTS.
METAL′LURGY. “The art of extracting metals from their ores, and adapting them to various processes of manufacture.” (Percy.)
“Notwithstanding the striking analogy which exists between common chemical and metallurgic operations, since both are employed to isolate certain bodies from each other, there are essential differences which should be carefully noted. In the first place, the quantity of materials being always very great in metallurgy, requires corresponding adaptations of apparatus, and often produces peculiar phenomena; in the second place, the agents to be employed for treating great masses must be selected with a view to economy, as well as chemical action. In analytical chemistry, the main object being exactness of result and purity of product, little attention is bestowed upon the value of the reagents, on account of the small quantity required for any particular process. But in smelting metals upon the large scale, profit being the sole object, cheap materials and easy operations are alone admissible.”[35]
[35] ‘Ure’s Dict. of Arts, Manufactures, and Mines,’ 4th edit.
The limits of this work do not permit of more than a general reference to the leading operations of metallurgy under this head. These are—digging, picking or sorting, stamping
or crushing, and washing, included under the general term, ‘dressing ore,’—roasting or calcination, which is either performed with the fuel in contact with the ore, or in reverberatory furnaces; and the liquation or reduction to the reguline form. The application of these processes is noticed under the leading metals. Those who desire to study the subject minutely are referred to the treatises of Dr Percy, Robert Hunt, Karsten, and Le Play.
MET′ALS. Syn. Metalla, L. Metals are elementary bodies, which are generally distinguished by their lustre and power of conducting heat and electricity. When their solutions are electrolysed, the metals always appear at the electro-negative surface, and are hence termed electro-positive elements.