e acids detonate.

(_e._) _Reduction._--If we deprive an oxidized substance of its
oxygen, we term the process _reduction_. This is effected by fusing
the substance under examination with another which possesses a greater
affinity for oxygen. The agents used for reduction are hydrogen,
charcoal, soda, cyanide of potassium, etc. Substances generally, when
in the unoxidized state, have such characteristic qualities, that they
cannot very readily be mistaken for others. For this reason, reduction
is a very excellent expedient for the purpose of discerning and
classifying many substances.

B. UTENSILS.

We shall give here a brief description of the most necessary apparatus
used for analysis in the dry way, and of their use.

_The Blowpipe_ is a small instrument, made generally out of brass,
silver, or German silver, and was principally used in earlier times
for the purpose of soldering small pieces of metals together. It is
generally made in the form of a tube, bent at a right angle, but
without a sharp corner. The largest one is about seven inches long,
and the smallest about two inches. The latter one terminates with a
small point, with a small orifice. The first use of the blowpipe that
we have recorded is that of a Swedish mining officer, who used it in
the year 1738 for chemical purposes, but we have the most meagre
accounts of his operations. In 1758 another Swedish mining officer, by
the name of Cronstedt, published his "Use of the Blowpipe in
Chemistry and Mineralogy," translated into English, in 1770, by Van
Engestroem. Bergman extended its use, and after him Ghan and the
venerable Berzelius (1821). The blowpipe most generally used in
chemical examinations is composed of the following parts: (_Fig._ 1.)
A is a little reservoir made air-tight by grinding the part B into it.
This reservoir serves the purpose of retaining the moisture with which
the air from the mouth is charged. A small conical tube is fitted to
this reservoir. This tube terminates in a fine orifice. As this small
point is liable to get clogged up with soot, etc., it is better that
it should be made of platinum, so that it may be ignited. Two of these
platinum tubes should be supplied, differing in the size of the
orifice, by which a stronger or lighter current of flame may be
projected from it. Metals, such as brass or German silver, are very
liable to become dirty through oxidation, and when placed between the
lips are liable to impart a d