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

236 COMPOUNDS OF THE RARE ELEMENTS.

Prepare a solution containing 25 g. of the reducing agent, and

add this to a solution of 25 g. of uranyl nitrate in 100 c.c. of water

until the solution is decolorized; a precipitate is formed which is

at first brown in color but changes to a lighter shade. Dissolve

the precipitate in hydrochloric acid, filter, and treat the nitrate
with a hot solution of 15 g. of oxalic acid in 120 c.c. of water.
About 26 g. of gray, finely-crystalline uranous oxalate are pre-
cipitated.
To purify the precipitate, dissolve it in a solution of neutral
ammonium oxalate, using 6 g. of the latter salt and 100 c.c. of
water for each 10 g. of uranous oxalate. Reprecipitate the salt
from the filtered solution by adding hydrochloric acid. After

some hours filter off the precipitate, wash it with water and with

alcohol, and dry it in the hot closet. Yield, 9 g. from each 10 g.

of the impure salt.

Ammonium Urano-oxalate, (NH 4 ) 4 [U\G 2 O 4 ) 4 ]. Digest 10 g. of

uranous oxalate with a solution of 5 g. of neutral ammonium oxa-

late in 50 c.c. of water; filter off the excess of uranous oxalate,

and precipitate the double salt from the nitrate by adding alco-
hol a little at a time. Allow the mixture to stand for one or two

days, and then filter off the crystal meal which has by that time

become coarser. Yield, 12 g.

Uranium Tetrachloride, UClt. Uranium tetrachloride is pre-

pared in the apparatus described under No. 166 (c), by passing per-

fectly dry chlorine over a mixture of uranium oxide, U 3 OS, and

one-eighth of its weight of ignited wood charcoal, the whole
being heated as hot as possible in a combustion furnace. The

principle is the same as that outlined under No. 52. Uranium

tetrachloride condenses in the front part of the tube, and is freed

from admixed pentachloride by heating it in a current of carbon

dioxide at about 150°. In this way a very hygroscopic mass of

greenish-black crystals is obtained. The tetrachloride dissolves

in water with evolution of heat, and yields a green solution (cf.

Uranous Oxalate).

170. Thorium Compounds from Monazite.

Thorium was first discovered by Berzelius in the rare Scandinavian min-
erals thorite and orangite. When the oxide of thorium became of industrial
importance through its use in the Welsbach incandescent mantles, a more