This material is a
deadly poison and should be handled with care. Allow the cyanide to fuse on
the surface of the metal and then plunge into water, brine or mercury.
Repeating the process makes the surface harder and the hard skin deeper
each time.
Another method consists of placing the piece to be hardened in a bed of
powdered bone (bone which has been burned and then powdered) and cover with
more powdered bone, holding the whole in an iron tray. Now heat the tray
and bone with the work in an oven to a bright red heat for 30 minutes to an
hour and then plunge the work into water or brine.
CHAPTER II
OXY-ACETYLENE WELDING AND CUTTING MATERIALS
_Welding._--Oxy-acetylene welding is an autogenous welding process, in
which two parts of the same or different metals are joined by causing the
edges to melt and unite while molten without the aid of hammering or
compression. When cool, the parts form one piece of metal.
The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a
special welding torch or blowpipe, producing, when burned, a heat of 6,300
degrees, which is more than twice the melting temperature of the common
metals. This flame, while being of intense heat, is of very small size.
_Cutting._--The process of cutting metals with the flame produced from
oxygen and acetylene depends on the fact that a jet of oxygen directed upon
hot metal causes the metal itself to burn away with great rapidity,
resulting in a narrow slot through the section cut.
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