224 HEAVY METALS OF GROUPS I AND IIchanges to a very light brown. Do not heat more than 15 min-
utes. While the reduction is taking place, pour 50 cc. of ether and
approximately 1,500 cc. of cold water into a 2-liter bottle. (Ether
is inflammable. Do not bring it within 3 feet of a flame.) The
ether serves to partly expel the oxygen dissolved in the water.
Shake the mixture and allow it to stand until the fine bubbles of
air have risen to the surface. When the cupric salt in the flask is
reduced as indicated by the change to a light brown color, pour it
so carefully into the water-ether mixture in the large bottle that
all solid particles of copper will be retained in the flask. Rinse
the flask with 20 cc. of 3 N HCl, and pour this with equal care into
the large bottle. Let the white precipitate settle. Moist cuprous
chloride darkens in direct light, and the bottle should not stand
near a window. Pour off most of the liquid, stir up the solid with
the rest, and pour the suspension into a suction filter. Use 50
cc. of water, to which 1 cc. of 6 N HCl has been added, to rinse all
the cuprous chloride into the funnel. The solid cuprous chloride
will settle on to the filter paper, and most of the liquid can be
decanted from the funnel if the filter runs too slowly. Continue
the suction until only a thin film of water covers the solid; stop
the suction. Pour 15 cc. of alcohol in a thin stream around the
upper edge of the funnel and let it run down, washing the sides
of the funnel and covering the cuprous chloride. Allow the alcohol
to soak into the solid, and when it begins to drip through the filter
plate, apply suction until only a thin film of alcohol covers the solid.
In exactly the same way wash the sides of the funnel and the
cuprous chloride with a second 15 cc. portion of alcohol and with
two successive 15-cc. portions of ether. Until the second portion
of ether is added, the solid cuprous chloride should not be allowed
to come in contact with the air. It should always be covered with
a thin film of the wash liquid. The second portion of ether should
be removed completely by applying suction.
If the cuprous chloride was not dried thoroughly it will turn
green on standing. This is due to the formation of basic cupric
chloride. The colored impurity may be removed by grinding the
preparation in a mortar with enough 0.5 N H2SO4 to make a thin
paste. When all the lumps have been removed pour the mixture
into 400 cc. of distilled water and repeat the filtration and wash-
ings with alcohol and ether.
Transfer the cake of cuprous chloride to a dry watch glass, re-