a, is of great purity,
and is called "Straits Tin" or "Stream Tin." It occurs in alluvial
deposits in the form of small rounded grains, which are washed, stamped,
mixed with slag and scoriae, and smelted with charcoal, then run into
basins, where the upper portion, after being removed, is known as the
best refined tin. Stream tin is not pure metallic tin, but is the result
of the disintegration of granitic and other rocks which contain veins of
tinstone. Banca tin is 99.961 parts tin, 0.019 iron, 0.014 lead in 100
parts; it is sold in blocks of 40 and 120 pounds, and a bar 0.5 meter
long, 0.1 broad, 0.005 deep can be bent seventy-four times without being
broken. Subjected to friction, tin emits a characteristic odor.

Tin in solution is largely used in electro-metallurgy for plating. Pure
tin may be obtained by dissolving commercial tin in hydrochloric acid,
by which it is converted into stannous chlorid; after filtering, this
solution is evaporated to a small bulk, and treated with nitric acid,
which converts it into stannic oxid, which in turn is thoroughly washed
and dried, then heated to redness in a crucible with charcoal, producing
a button of tin which is found at the bottom of the crucible.

Pure tin may be precipitated in quadratic crystals by a slight galvanic
current excited by immersing a plate of tin in a strong solution of
stannous chlorid; water is carefully poured in so as not to disturb the
layer of tin solution; the pure metal will be deposited on the plate of
tin, at the point of junction of the water and metallic solution.

In the study of tin as a material for filling teeth, we have deemed it
expedient to consider some of its physical characteristics, in order
that what follows may be more clearly understood.

Tin possesses a crystallized structure, and can be obtained in
well-formed crystals of the tetragonal or quadratic system (form right
square prism), and on account of this crystalline structure, a bar of
tin when bent emits a creaking sound, termed the "cry of tin;" the purer
the tin the more marked the cry.

The specific gravity is 7.29; electrical state positive; fusing point
442 deg. F.; tensile strength per square inch in tons, 2 to 3. Tensile
strength is the resistance of the fibers or particles of a body to
separation, so that the amount stated is the weight or power required
to tear asunder a bar of pure tin having a cross-section of one square
inch.

Tenacity: Iron is the most te