radio-active. Pitchblende or uraninite is an intensely black mineral
of a specific gravity of 9.5 and is found in commercial quantities in
Bohemia, Cornwall in England and some other localities. It contains
lead sulphide, lime silica, and other bodies.

To the radio-active substance which accompanied the bismuth extracted
from pitchblende the Curies gave the name _Polonium_. To that which
accompanied barium taken from the same ore they called _Radium_ and to
the substance which was found among the rare earths of the pitchblende
Debierne gave the name _Actinium_.

None of these elements have been isolated, that is to say, separated
in a pure state from the accompanying ore. Therefore, _pure radium_
is a misnomer, though we often hear the term used. [Footnote: Since
the above was written Madame Curie has announced to the Paris Academy
of Sciences that she has succeeded in obtaining pure radium. In
conjunction with Professor Debierne she treated a decegramme of bromide
of radium by electrolytic process, getting an amalgam from which was
extracted the metallic radium by distillation.] All that has been
obtained is some one of its simpler salts or compounds and until
recently even these had not been prepared in pure form. The commonest
form of the element, which in itself is very far from common, is what
is known to chemistry as chloride of radium which is a combination of
chlorin and radium. This is a grayish white powder, somewhat like
ordinary coarse table salt. To get enough to weigh a single grain
requires the treatment of 1,200 pounds of pitchblende.

The second form of radium is as a bromide. In this form it costs $5,000
a grain and could a pound be obtained its value would be
three-and-a-half million dollars.