_Of_ TIN.
Tin is the lightest of all metals. Though it yields easily to the
impression of hard bodies, it has but little ductility. Being bent
backwards and forwards it makes a small crackling noise. It flows with
a very moderate degree of fire, and long before it comes to be red-hot.
When it is in fusion, its surface soon grows dusty, and there forms
upon it a thin dark-coloured dusty pellicle, which is no other than a
part of the Tin that has lost its phlogiston, or a calx of Tin. The
metal thus calcined easily recovers its metalline form on the addition
of a phlogiston. If the calx of Tin be urged by a strong fire it grows
white, but the greatest violence of heat will not fuse it; which makes
some Chymists consider it as a calcinable or absorbent earth, rather
than a vitrifiable one. Yet it turns to glass, in some sort, when mixed
with any other substance that vitrifies easily. However, it always
produces an imperfect glass only, which is not at all transparent, but
of an opaque white. The calx of Tin thus vitrified is called _Enamel_.
Enamels are made of several colours by the addition of this or that
metalline calx.
Tin unites easily with all the metals; but it destroys the ductility
and malleability of every one of them, Lead excepted. Nay, it possesses
this property of making metals brittle in such an eminent degree, that
the very vapour of it, when in fusion, is capable of producing this
effect. Moreover, which is very singular, the most ductile metals, even
Gold and Silver, are those on which it works this change with the most
ease, and in the greatest degree. It has also the property of making
Silver mixed with it flow over a very small fire.
It adheres to, and in some measure incorporates with, the surface of
Copper and of Iron; whence arose the practice of coating over those
metals with Tin. Tin plates are no other than thin plates of Iron
tinned over.
If to twenty parts of Tin one part of Copper be added, this alloy
renders it much more solid, and the mixed mass continues tolerably
ductile.
If, on the contrary, to one part of Tin ten parts of Copper be added,
together with a little Zink, a semi-metal to be considered hereafter,
from this combination there results a metalline compound which is hard,
brittle, and very sonorous; so that it is used for casting bells: this
composition is called _Bronze_ and _Bell-metal_.
Tin hath an affinity with the vitriolic, nitrous, and marine acids. All
of them attack and corrode it; yet none of them is able to dissolve
it without great difficulty: so that if a clear solution thereof be
desired, particular methods must be employed for that purpose; for the
acids do but in a manner calcine it, and convert it to a kind of white
calx or precipitate. The solvent which has the greatest power over it
is _aqua regis_, which has even a greater affinity therewith than with
Gold itself; whence it follows, that Gold dissolved in _aqua regis_
may be precipitated by means of Tin; but then the _aqua regis_ must be
weakened. Gold thus precipitated by Tin is of a most beautiful colour,
and is used for a red in enameling and painting on porcelain, as also
to give a red colour to artificial gems. If the _aqua regis_ be not
lowered, the precipitate will not have the purple colour.
Tin hath the property of giving a great lustre to all red colours
in general; on which account it is used by the dyers for striking a
beautiful scarlet, and tin vessels are employed in making fine syrup
of violets. Water does not act upon this metal, as it does upon Iron
and Copper; for which reason it is not subject to rust: nevertheless,
when it is exposed to the air, its surface soon loses its polish and
splendour.
Tin mixed with nitre and exposed to the fire deflagrates with it, makes
it detonate, and is immediately converted to a _refractory calx_: for
so all substances are called which are incapable of fusion.
Tin readily unites with sulphur, and with it becomes a brittle and
friable mass.