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

WORKING UP OF PITCHBLENDE. 231

Tungsten Trioxide, WO 3. This oxide can be obtained by heat-

ing either of the above acids, or it can be formed directly from

ammonium tungstate by heating the salt in a porcelain crucible

at first over a Bunsen flame and finally over a blast lamp. The

oxide is a lemon-yellow powder which in the Sunlight acquires a

greenish tinge.

(c) Tungsten Hexachloride, WCle.

First prepare metallic tungsten, as a grayish-black powder, by

reducing the trioxide in an atmosphere of hydrogen at the highest

temperature obtainable in the combustion furnace. (Cf. the prep-
aration of molybdenum under Molybdenum Pentachloride, p. 224.)
Prepare tungsten hexachloride from the metallic tungsten

according to the directions for obtaining molybdenum penta-
chloride from molybdenum (p. 224). Here also it is important

to exclude moisture and atmospheric oxygen with the greatest

care. On passing chlorine over the metal some yellow tungsten

oxychloride is formed at first; expel this by heating the tube with
a free flame, and allow the vapors to condense only when they

have become dark colored. The hexachloride is a dark-violet,

very hygroscopic, crystalline powder, which must be preserved

in a sealed tube. Light and air change it to yellow tungstyl
chloride, WO 2 C1 2.

168. Working Up of Pitchblende and Testing of the Components

for Radioactivity.

Becquerel discovered in 1896 that pitchblende and uranium preparations
send out peculiar radiations which, like the Roentgen rays, can be detected
by their action upon photographic plates, and by their ability to make the
air through which they pass a conductor of electricity. These radiations
are called Becquerel rays, and the substances emitting them are said to be
radioactive. By separating pitchblende into its constituents and by testing
each for its radioactivity, M. and Mme. Curie (1898) established the fact
that the ability to emit Becquerel rays becomes concentrated in certain
definite constituents; the barium sulphate, which they prepared from the
barium residues obtained in the technical working up of the ore, was found
to be particularly active; and from this they succeeded in isolating a new
element, radium, which showed to the very highest degree the property of
radioactivity. The lead, bismuth, uranium, and rare earths obtained from
pitchblende are also radioactive, although to a lesser degree.