finely divided carbon. Five parts of tartar should be used in the place
of one of charcoal.

~Anthracite~ or ~Culm~ is a kind of coal containing 90 per cent. or more
of carbon. It gives off no inflammable gas. It is denser, and takes
longer in burning, than charcoal. Its reducing effect is little inferior
to that of charcoal. Almost any organic substance can be used as a
reducing agent, but it is well not to select one which melts, swells up,
or gives off much water and gas when heated in the furnace.

~Potassic Cyanide~ is an easily fusible and somewhat volatile salt,
which, when fused, readily removes oxygen and sulphur from metallic
compounds, and forms potassic cyanate or sulphocyanate as the case may
be. Commercial samples vary much in purity; some contain less than 50
per cent. of the salt. For assaying, only the better qualities should be
used.

~Iron~ is a de-sulphurising rather than a de-oxidising agent. Iron is
used in the form of rods, 1/2-inch in diameter, or of nails, or of hoop
iron. In the last case it should be thin enough to be bent without
difficulty. Wrought iron crucibles are very useful in the processes
required for making galena assays.

_The chief oxidising agents (which are also de-sulphurisers)_ are the
following:--

~Nitre~, or Potassic Nitrate.--This salt fuses very easily to a watery
liquid. It oxidises most combustible substances with deflagration, and
thereby converts sulphides into sulphates, arsenides into arsenates, and
most metals into oxides. In the presence of strong bases, such as soda,