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

220 COMPOUNDS OF THE RARE ELEMENTS.

water; again evaporate the solution to dryness, and dehydrate

the residue completely by heating to about 160°. Extract the

residue with absolute alcohol either in a Soxhlet apparatus or in

a simple flask with a return condenser. In the latter case, extract

eight times and distil each of the alcoholic solutions poured from

the insoluble residue, using the alcohol, thus recovered, for the

next extraction. Finally, after all of the alcohol has been dis-

tilled from the extract, dissolve the salt in a little water and

precipitate lithium carbonate by adding ammonium carbonate

and a little ammonia. From lepidolite 1 to 3 g. of pure lithium

carbonate should be obtained, from petalite a little more, and

from spodumene about twice as much. Test the purity of the

preparation by means of the spectroscope.

The insoluble salt left by the alcoholic extraction contains

rubidium, besides other of the alkali metals. Dissolve it in

water, treat the solution with about 1 c.c. of 10% chlorplatinic

acid solution, and allow it to stand over night. Next morning

filter off the insoluble chlorplatmates and ignite them in a Rose

crucible in a current of hydrogen. Dissolve the residue in a

little water and test it with the spectroscope for rubidium.

Spectroscopic Analysis.

The scale of the spectroscope, which is usually graduated arbi-
trarily, must first be standardized according to the wave lengths
of light. After the apparatus is properly set up, make the
sodium line fall upon a certain division of the scale; or, in case

the scale telescope is not movable, observe the position of this

line as accurately as possible. Then note the position of the

following lines:

Kared

Lia red

Na yellow

Tl green

768

671

589

535

Wave Length

X 10-e mm.

it

it

Src

Ha

H/3

Hv

blue

red

blue

violet

Wave Length

461 X 10-"mi

656

486

434

The hydrogen lines are very sharp and easy to observe; ready

prepared tubes filled with hydrogen under diminished pressure
can be used, and are to be excited by means of an induction coil.

Plot the scale readings as abscissas and the corresponding wave