MANGANOUS CHLORIDE. 77
- Barium Chloride from Witherite.
If a sample of witherite is dissolved in hydrochloric acid, the resulting
solution of barium chloride contains iron as well as other impurities. The
simplest way to remove the iron is to oxidize it with a little chlorine water,
and then precipitate it by adding an excess of the powdered mineral (cf. the
barium carbonate method for the analytical separation of metals, the salts
of which hydrolyze to different degrees; see p. 68). The more difficultly
soluble barium chloride is freed from any calcium and strontium chlorides by
crystallization.
First determine with a Westphal balance the density of the
pure, concentrated hydrochloric acid which is to be used, findthe percentage of HC1 by referring to specific gravity tables, and
compute the volume of the acid required to dissolve 100 g. of
witherite. Place this amount in a two-liter flask, dilute it with
water to a volume of 1500 c.c, add the powdered witherite and
heat until the mineral is dissolved. Impurities such as silicates
may remain as insoluble residue. Add 50 c.c. of chlorine water,
then 5 to 10 g. more of witherite, and allow the solution to stand
in a warm place with frequent shaking. Next morning again add
from 2 to 5 g. of witherite. From time to time filter a little of the
solution and test with potassium thiocyanate for iron. When all
the iron has been precipitated, filter, and evaporate the filtrate
until crystallization takes place. If during the evaporation any
more ferric hydroxide, which may have been held in colloidal
solution, separates, filter it off after the volume has been reduced
to one-half. Finally, drain the crystals of barium chloride in a
funnel and concentrate the mother liquor for more crystals.
Redissolve all the crystals in water, acidify with a few drops of
hydrochloric acid, filter and recrystallize. Yield, 100 to 110 g. of
BaCl 2 • 2 H 2 O.
- Manganous Chloride from Waste Manganese Liquors.
Pure manganous chloride can be obtained by crystallizing the waste liquor
obtained in the preparation of chlorine from pyrolusite and hydrochloric
acid, if, as in the last preparation, the iron is first removed.
Similarly, the waste liquor from hydrogen generators can be freed from
iron and worked up into pure zinc salts.
Evaporate 2 to 3 liters of the manganese liquor in a porcelain