distillation.

Many of the physical properties of zinc are much influenced by the
temperature and previous treatment of the metal. When cast into ingots
from the liquid state it becomes at ordinary temperatures quite hard,
brittle, and highly crystalline. At 150 deg. it is malleable and can be
rolled into thin sheets; at higher temperatures it again becomes very
brittle. When once rolled into sheets it retains its softness and
malleability at ordinary temperatures. When melted and poured into water
it forms thin brittle flakes, and in this condition is called granulated
or mossy zinc.

~Chemical properties.~ Zinc is tarnished superficially by moist air, but
beyond this is not affected by it. It does not decompose even boiling
water. When the metal is quite pure, sulphuric and hydrochloric acids
have scarcely any action upon it; when, however, it contains small
amounts of other metals such as magnesium or arsenic, or when it is
merely in contact with metallic platinum, brisk action takes place and
hydrogen is evolved. For this reason, when pure zinc is used in the
preparation of hydrogen a few drops of platinum chloride are often added
to the solution to assist the chemical action. Nitric acid dissolves the
metal readily, with the formation of zinc nitrate and various reduction
products of nitric acid. The strong alkalis act upon zinc and liberate
hydrogen:

Zn + 2KOH = Zn(OK)_{2} + 2H.

The product of this reaction, potassium zincate, is a salt of zinc
hydroxide, which is thus seen to have acid properties, though it usually
acts as a base.

~Uses of zinc.~ The metal has many familiar uses. Rolled into sheets, it
is used as a lining for vessels which are to contain water. As a thin
film upon the surface of iron (galvanized iron) it protects the iron
from rust. Iron is usually galvanized by dipping it into a bath of
melted zinc, but electrical methods are also employed. Zinc plates are
used in many forms of electrical batteries. In the laboratory zinc is
used in the preparation of hydrogen, and in the form of zinc dust as a
reducing agent.

One of the largest uses of zinc is in the manufacture of alloys. Brass,
an alloy of zinc and copper, is the most important of these; German
silver, consisting of copper, zinc, and nickel, has many uses; various
bronzes, coin metals, and bearing metals also contain zinc. Its ability
to alloy with silver finds application in the separation of silver from
lead (see silver).