after cooling. There are many other metallic sulphides, which, when
heated by the blowpipe flame, cover the charcoal with a white
incrustation, as sulphide of antimony, sulphide of zinc, and sulphide
of tin. In all these cases, however, the incrustation consists of the
metallic oxide alone, and either volatilizes or remains unchanged,
when submitted to the oxidizing flame.

Of the metallic chlorides there are many which, when heated on
charcoal with the blowpipe flame, are volatilized and redeposited as a
white incrustation. Among these are the chlorides of potassium,
sodium, and lithium, which volatilize and cover the charcoal
immediately around the assay with a thin white film, after they have
been fused and absorbed into the charcoal, chloride of potassium forms
the thickest deposit, and chloride of lithium the thinnest, the
latter being moreover of a greyish-white color. The chlorides of
ammonium, mercury, and antimony volatilize without fusing.

The chlorides of zinc, cadmium, lead, bismuth, and tin first fuse and
then cover the charcoal with two different incrustations, one of which
is a white volatile chloride, and the other a less volatile oxide of
the metal.

Some of the incrustations formed by metallic chlorides disappear with
a colored flame when heated with the reducing flame; thus chloride of
potassium affords a violet flame, chloride of sodium an orange one,
chloride of lithium a crimson flame, and chloride of lead a blue one.
The other metals mentioned above volatilize without coloring the
flame.

The chloride of copper fuses and colors the flame of a beautiful blue.