232 COMPOUNDS OF THE RARE ELEMENTS.
Uranium compounds are obtained technically from pitchblende by digest-
ing the ore with nitric acid, evaporating to dryness, and extracting the
residue with water; uranyl nitrate is crystallized from the solution. The
insoluble material is then extracted with a large amount of sodium carbonate
solution, whereby the rest of the uranium is dissolved as sodium uranyl car-
bonate. The residues from this treatment form the starting material for
obtaining radium.
This discovery of radium and radioactivity was epoch-making for both
physics and chemistry. So intense has the investigation of radioactivity
become that special journals giving original literature and references to all
work performed in this field are now published both in English and German.Pulverize 10 to 15 g. of pitchblende as finely as possible, and
digest the powder for several hours on the water bath with a
mixture of 20 g. of concentrated nitric acid and an equal amount
of water. Evaporate the mixture to dryness, and treat the resi-
due twice successively with 5 g. of the same acid mixture, evapo-
rating each time to dryness. Extract the dry mass with water
and evaporate the filtrate on the water bath. Place the dry
residue from the aqueous solution in a flask, and extract it several
times with warm ether until nothing more dissolves; evaporate
the ethereal solution of uranyl nitrate, taking care that the
vapor does not take fire. Dissolve the salt in water, precipitate
it with ammonia, and ignite the precipitate to uranium octo-
oxide, U 3 O 8.
Treat with aqua regia the water-insoluble residue from the
nitric acid treatment, and evaporate the mass to dryness. Moisten
the residue with a little concentrated hydrochloric acid, extract
it with hot water, and combine the solution with an aqueous solu-
tion of the residue left from the extraction with ether.
Separate the constituents of the solution thus obtained accord-
ing to the usual procedure of qualitative analysis. The working
up of the hydrogen sulphide precipitate yields: (1) As, Sb, Sn;
(2) Pb; (3) Bi; (4) Cu. Dissolve the ammonium sulphide pre-
cipitate in hydrochloric acid, oxidize the solution, and precipitate
Fe, Al, and the rare earths with ammonia. Treat this pre-
cipitate immediately with concentrated sodium carbonate solu-
tion, whereby the remainder of the uranium dissolves; it can be
precipitated by caustic soda from this solution as sodium pyro-
uranate. Dissolve the residue from the sodium carbonate treat-
ment in as little hydrochloric acid as possible, nearly neutralize