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.
Moreover, if a continuous blast be directed upon the salt, a part of
it is driven off in the form of white fumes which smell strongly of
chlorine, and the charcoal is covered with incrustations of three
different colors. That which is formed nearest to the assay is of a
dark grey color, the next, a dark yellow passing into brown, and the
most distant of a bluish white color. If this incrustation be heated
under the reducing flame, it disappears with a blue flame.

Metallic iodides and bromides behave upon charcoal in a similar manner
to the chlorides. Those principally deserving of mention are the
bromides and iodides of potassium and sodium. These fuse upon
charcoal, are absorbed into its pores, and volatilize in the form of
white fumes, which are deposited upon the charcoal at some distance
from the assay. When the saline films so formed are submitted to the
reducing flame, they disappear, coloring the flame in the same manner
as the corresponding chlorides.

4. EXAMINATIONS IN THE PLATINUM FORCEPS.

Before the student attempts to make an examination in the platinum
forceps or tongs, he should first ascertain whether or not it will
act upon the platinum. If the substance to be examined shall act
chemically upon the platinum, then it should be examined on the
charcoal, and the color of t