xposure.
The colouring-matter of Brazil wood, brazilin, C16H14O5, crystallizes
with 1-1/2 H2O, and is freely soluble in water; it is extracted for use by
simple infusion or decoction of the coarsely-powdered wood. When freshly
prepared the extract is of a yellowish tint; but by contact with the
air, or the addition of an alkaline solution, it develops a brick-red
colour. This is due to the formation of brazilein, C16H12O5.H2O, which
is the colouring matter used by the dyer. Brazilin crystallizes in
hexagonal amber yellow crystals, which are soluble in water and alcohol.
The solution when free of oxygen is colourless, but on the access of air
it assumes first a yellow and thereafter a reddish yellow colour. With
soda-ley it takes a brilliant deep carmine tint, which colour may be
discharged by heating in a closed vessel with zinc dust, in which
condition, the solution is excessively sensitive to oxygen, the
slightest exposure to air immediately giving a deep carmine. With tin
mordants Brazil wood gives brilliant but fugitive steam reds in
calico-printing; but on account of the loose nature of its dyes it is
seldom used except as an adjunct to other colours. It is used to form
lakes which are employed in tinting papers, staining paper-hangings, and
for various other decorative purposes.

BRAZING AND SOLDERING, in metal work, termed respectively hard and soft
soldering, are processes which correspond with soldering done at high
and at low temperatures. The first embraces jointing effected with
soldering mixtures into which copper, brass, or silver largely enter,
the second those in which lead and tin are the only, or the principal,
constituents. Some metals, as aluminium and cast iron, are less easily
soldered than others. Aluminium, owing to its high conductivity, removes
the heat from the solder rapidly. Aluminium enters into the composition
of most of the solders for these metals, and the "soldering bit" is of
pure nickel.

The hard solders are the spelter and the silver solders. Soft spelter
solder is composed of equal parts of copper and zinc, melted and
granulated and passed through a sieve. As some of the zinc volatilizes
the ultimate proportions are not quite equal. The proportion of zinc is
increased if the solder is required to be softer or more fusible. A
valuable property of the zinc is that its volatilization indicates the
fusing of the solder. Silver solder is used for jewelry and other fine
metal wor