ire and is converted with considerable intensity into the acids,
producing white vapors. This is likewise the case if it is touched by
a spark of fire from steel. The hydrate of the protoxide of tin can be
ignited by the flame of a candle, and glows like tinder.

([beta].) _Sesquioxide of Tin_ (Sn^{2}O^{3}) is a greyish-brown
powder. Its hydrate is white, with a yellow tinge. It is soluble in
aqua ammonia and in hydrochloric acid; this solution forms with
solution of gold the "purple of Cassius."

([gamma].) _Stannic Acid_ (peroxide, SnO^{2}).--This acid occurs in
nature crystallized in quadro-octahedrons, of a brown or an intense
black color, and of great hardness (tinstone). Artificially prepared,
it is a white or yellowish-white powder. It exists in two distinct or
isomeric modifications, one of which is insoluble in acids (natural
tin-acid) while the other (tin-acid prepared in the wet way) is
soluble in acids. By ignition the soluble acid is converted into the
insoluble. Both modifications form hydrates.

_Reactions before the Blowpipe._--Metallic tin melts easily. It is
covered in the flame of oxidation into a yellowish-white oxide, which
is carried off sometimes by the stream of air which propels the flame.
In the reduction flame, and upon charcoal, melting tin retains its
metallic lustre, while a thin sublimate is produced upon the charcoal.
This sublimate is light-yellow while hot, and gives a strong light in
the flame of oxidation, and turns white while cooling. This sublimate
is found near to the metal, and cannot be volatilized in the oxidation
flame. In the flame of reduction it is reduced to metallic tin.
Sometimes this incrustation is so imperceptible that it can scarcely
be distinguished from the ashes of the charcoal. If such be the case,
moisten it with a solution of cobalt, and expose it to the flame of
oxidation, when the sublimate will exhibit, after cooling, a
bluish-green color.

Protoxide of tin takes fire in the flame of oxidation, and burns with
flame and some white vapor into tin acid, or stannic acid. In a strong
and continued reduction flame, it may be reduced to metal, when the
same sublimate above mentioned is visible. The sesquioxide of tin
behaves as the above.

Stannic acid, heated in the flame of oxidation, does not melt and is
not volatilized, but produces a strong light, and appears yellowish
while hot, but changing as it cools to a dirty-yellow white color. In
a strong and con