Laboratory Methods of Inorganic Chemistry, 2nd English Ed. 1928

246 COMPOUNDS OF THE RARE ELEMENTS.

(c) Didymium Compounds.

Dissolve the didymium precipitate in as little warm nitric acid

as possible, and treat the solution with magnesium oxide, as

directed in the didymium-lanthanum separation, until the didy-

mium lines are only just faintly visible. Drain and wash the

resulting precipitate, dissolve it in hydrochloric acid, and repre-

cipitate the didymium with ammonium carbonate; in order to

remove the last traces of magnesium, dissolve and again reprecipi-

tate the didymium carbonate. The preparation thus obtained

consists chiefly of the neodymium salt, and is consequently pink

in color. A separation from praseodymium is not possible on a

small scale.

Didymium Chloride voith Alcohol of CrystallizationjDiClfSCJIsOH.

Ignite 5 g. of didymium carbonate in a platinum crucible, dissolve

the powdered didymium oxide by boiling with a saturated solu-

tion of dry hydrogen chloride in anhydrous alcohol (about 50 c.c.
are necessary), and filter the yellow solution, which has the con-

sistency of thin sirup, through a felt of asbestos in a Gooch cruci-

ble. Saturate the nitrate with dry hydrogen chloride gas. Drain

the large light-red crystals which separate in the course of several
hours, and wash them with a little alcohol. Yield, 6 to 7 g.
Didymium Sulphide and Anhydrous Didymium Chloride can be
prepared according to the methods given for the corresponding
cerium compounds.