h air, it produces the most
annoying irritation of the throat, with stricture of the chest and a
severe cough, which continues for hours, with the discharge of much
thick mucus. The attempt to breathe the undiluted gas would be fatal;
yet, in a very small quantity, and dissolved in water, it is used with
benefit by patients suffering under pulmonary consumption.

Under a pressure of about four atmospheres, it becomes a limpid fluid
of a fine yellow color, which does not freeze at zero, and is not a
conductor of electricity. It immediately returns to the gaseous state
with effervescence on removing the pressure.

Water recently boiled will absorb, if cold, about twice its bulk of
chlorine gas, acquiring its color and characteristic properties. The
moist gas, exposed to a cold of 32 deg., yields beautiful yellow
crystals, which are a definite compound of one equivalent of chlorine
and ten of water. If these crystals are hermetically sealed up in a
glass tube, they will, on melting, exert such a pressure as to liquefy
a portion of the gas, which is distinctly seen as a yellow fluid, not
miscible with the water which is present. Chlorine is one of the
heaviest of the gases, its density being 2.47, and 100 cubic inches
weighing 76.5 grains.

Chlorine Water.--This combination, which is used in conducting M.
Neipce's process, can be readily prepared by conducting the gas into a
bottle containing distilled water. One part water dissolves two parts
of chlorine.

Chlorides.--The metallic chlorides are nearly all soluble in water;
that of silver and protochloride of mercury being the only exceptions.
A metallic chloride, treated with oil of vitriol, disengages
chlorohydric acid. Heated with a mixture of peroxide of manganese and
sulphuric acid, chlorine is given off, which is easily recognized by
its odor and other physical properties.

The chlorides dissolve in water; give with nitrate of silver, a white
precipitate, even in highly diluted solutions, becoming violet colored
and finally black when exposed to the light. The rapidity of the
change of color is proportioned to the intensity of the light. It is
insoluble in nitric acid, but readily soluble in ammonia; it fuses
without decomposition, forming, when cold, a tough, horny mass, and is
reduced by hydrogen and by fusion with carbonate of soda, or with resin.

Chloride of Bromine. (See page 74.)

Chloride of Iodine. (See page 85.)

Chloride of potassium.--