Chemical Reaction of the more Important Elements.
It
is not intended in this place to describe the chemical nature of the
elementary substances, and still less to enumerate the whole of those
marks by which the chemist can detect their presence. Our object is
limited principally to the conduct of minerals before the blowpipe, and
to a few simple tests by which their more important constituents may be
discovered by the student.
I.----NON-METALLIC ELEMENTS, AND THEIE COMBINATIONS
WITH OXYGEN.
Nitric Acid.—Most
of its salts detonate when heated on charcoal. In the closed tube they
form nitrous acid, easily known by its orange color and smell; a test
more dearly exhibited when the salt is mixed with copper filings and
treated with concentrated sulphuric acid. When to the solution of a
nitrate, a fourth part of sulphuric acid is added, and a fragment of
green vitriol placed in it, the surrounding fluid becomes of a
dark-brown color.
Sulphur and
its compounds, in the glass tube or on charcoal, form sulphurous
acid,' easily known by its smell. The minutest amount of sulphur or
sulphuric acid may be detected by melting the pulverized assay with
two parts soda and one part borax, and placing the bead moistened with
water on a plate of clean silver, which is then stained brown or black.
Solutions of sulphuric acid give with chloride of barium a heavy white
precipitate, insoluble in acids.
Phosphoric Acid.—Most
combinations with this acid tinge the blowpipe flame green, especially
if previously moistened with sulphuric acid. The experiment must be
performed in the dark, when even three per cent, of the acid may be
detected. If the assay is melted with six parts
