CHAPTER VII.
PREPARATION OF COMPOUNDS OF THE RARE
ELEMENTS FROM THEIR MINERALS.IN this chapter methods are described for preparing compounds of some
of the rarer elements. It has seemed advisable to devote to these elements a
special chapter in which the chief stress is laid upon the methods of working
up the natural raw materials, and upon the characterization of the individual
elements by the aid of their compounds, rather than upon a classification of
the compounds according to types.- Lithium Carbonate from Lepidolite, Petalite, or Spodumene;
Spectroscopic Tests for Rubidium and Other Metals.
Mix 100 g. of the finely powdered mineral intimately with 100 g.
of ammonium chloride and 200 g. of finely powdered calcium
carbonate; heat the mixture in a clay crucible, at first gently for
half an hour, and then strongly for an hour in the furnace.
Break up the sintered mass and extract it about ten times by
boiling with 750 to 1000 c.c. of water in a large evaporating dish.
Pour off the solution each time through a plaited filter and begin
at once to concentrate the filtrate in a second evaporating dish.
After the entire filtrate has been reduced to about one liter,
make it alkaline with ammonia and add ammonium carbonate
until a little of the liquid when filtered gives no further precipi-
tation with the reagent. Drain the solution, on a suction filter,
from the precipitated calcium carbonate, and, as the latter con-
tains some lithium carbonate, dissolve it in acetic acid, dilute to
about 1.5 liters and precipitate this solution cold with oxalic
acid. After the precipitate has settled, filter and add the filtrate
to the main solution of the lithium salt. Evaporate the entire
solution to dryness, and drive off the ammonium salts from the
residue by gentle ignition. Then moisten the substance with
concentrated hydrochloric acid and dissolve it in a little hot
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