liquid will instantly assume a blue color. Advantage is taken of this
fact in the laboratory to detect the presence of iodine in liquids.
The starch should be dissolved in boiling water and allowed to cool.
There are numerous other interesting experiments that can be performed
by the aid of iodine, but it is unnecessary here to consume more space.

CHLORINE.

History.--The Swedish chemist, Scheele, in 1774, while examining the
action of hydrochloric acid on peroxide of manganese, first noticed
this element. He called it dephlogisticated muriatic acid. It was
afterwards, by the French nomenclaturists, termed oxygenated muriatic
acid, conceiving it to be a compound of oxygen and muriatic acid. This
view of its notice was corrected by Sir H. Davy (in 1809), who gave it
the present name. In 1840-41, this gas vas employed for accelerating
the operation of light upon the iodized Daguerreotype plate. John
Goddard, Wolcott & Johnson, Claudet, Draper, Morse and others, were
among the first made acquainted with its use. Count Rumford, Ritter,
Scheele, Seebert and others, experimented with chlorine in regard to
its effect when exposed to the action of light in combination with
silver. In 1845, M. Edward Becquerel announced that he had "been
successful in obtaining, by the agency of solar radiations, distinct
impressions, of the colors of nature."

On the 4th of March, 1851, Neipce, St. Victor, a former partner of
DAGUERRE, announced that he had produced "all the colors by using a
bath of bichloride of copper, and that a similar phenomenon occurs with
all salts of copper, mixed with chlorine."

Preparation.--This is easily accomplished by putting about two parts of
hydrochloric (muriatic) acid on one of powdered black oxide of
manganese, and heating it gradually in a flask or retort, to which may
be adapted a bent glass tube. A yellowish-green gas is disengaged,
which being conducted through the glass tube to the bottom of a bottle,
can readily be collected, being much heavier than the air, displaces it
completely and the bottle is filled (which can be seen by the green
color); a greased stopper is tightly fitted to it, and another bottle
may be substituted.

In all experiments with chlorine, care should be taken not to inhale
the gas!

Properties.--Chlorine is a greenish-yellow gas (whence its name, from
chloros, green), with a powerful and suffocating odor, and is wholly
irrespirable. Even when much diluted wit