oxygen of the red lead is thus available for oxidising purposes. If this
oxidising power is prejudicial, it may be neutralised by mixing the red
lead with 1 per cent. of charcoal.

~Glass~: broken beakers and flasks, cleaned, dried, and powdered will
do. It should be free from lead.

~Fluor~: fluor-spar as free as possible from other minerals, powdered.
It helps to flux phosphate of lime, &c., and infusible silicates.

~Lime~: should be fresh and powdered. It must not be slaked. Powdered
white marble (carbonate of lime) will do; but nearly double the quantity
must be taken. One part of lime produces the same effect as 1.8 parts of
the carbonate of lime.

~Tartar~ and "black flux," are reducing agents as well as fluxes. The
"black flux," which may be obtained by heating tartar, is a mixture of
carbonate of potash and charcoal.

REDUCING AGENTS.--The distinction between reducing agents and fluxes
(too often ignored) is an important one. Fluxes yield slags; reducing
agents give buttons of regulus or of metal. The action of a reducing
agent is the separation of the oxygen or sulphur from the metal with
which it is combined. For example, the mineral anglesite (lead sulphate)
is a compound of lead, sulphur, and oxygen; by carefully heating it with
charcoal the oxygen is taken away by the charcoal, and a regulus of lead
sulphide remains. If the regulus be then fused with metallic iron the
sulphur is removed by the iron, and metallic lead is left. The charcoal
and the iron are reducing agents. But in defining a reducing agent as
one which removes oxygen, or sulphur, from a metallic compound so as to