I spent some time in studying the way of making good measurements of
the uranium rays, and then I wanted to know if there were other
elements, giving out rays of the same kind. So I took up a work
about all known elements, and their compounds and found that uranium
compounds are active and also all thorium compounds, but other
elements were not found active, nor were their compounds. As for the
uranium and thorium compounds, I found that they were active in
proportion to their uranium or thorium content. The more uranium or
thorium, the greater the activity, the activity being an atomic
property of the elements, uranium and thorium.
Them I took up measurements of minerals and I found that several of
those which contain uranium or thorium or both were active. But then
the activity was not what I could expect, it was greater than for
uranium or thorium compounds like the oxides which are almost
entirely composed of these elements.
Then I thought that there should be in the minerals some unknown
element having a much greater radioactivity than uranium or thorium.
And I wanted to find and to separate that element, and I settled to
that work with Professor Curie. We thought it would be done in
several weeks or months, but it was not so. It took many years of
hard work to finish that task. There was not one new ,lenient, there
were several of them. But the most important is radium, which could
be separated in a pure state.
Now, the special interest of radium is in the intensity of its rays
which several million times greater than the uranium rays. And the
effects of the rays make the radium so important. If we take a
practical point of view, then the most important property of the
rays is the production of physiological effects on the cells of the
human organism. These effects may be used for the cure of several
diseases. Good results have been obtained in many cases. What is
considered particularly important is the treatment of cancer. The
medical utilization of radium makes it necessary to get that element
in sufficient quantities. And so a factory of radium was started to
begin with in France, and later in America where a big quantity of
ore named carnotite is available. America does produce many grams of
radium every year, but the price is still very high because the
quantity of radium contained in the ore is so small. The radium is
more than a hundred thousand times dearer than gold.
But we must not forget that when radium was discovered no one knew
that it would prove useful in hospitals. The work was one of pure
science. And this is a proof that scientific work must not be
considered from the point of view of the direct usefulness of it. It
must be done for itself, for the beauty of science, and then there
is always the chance that a scientific discovery may become like the
radium a benefit for humanity.
The scientific history of radium is beautiful. The properties of the
rays have been studied very closely. We know that particles are
expelled from radium with a very great velocity near to that of the
light. We know that the atoms of radium are destroyed by expulsion
of these particles, some of which are atoms of helium. And in that
way it has been proved that the radioactive elements are constantly
disintegrating and that they produce at the end ordinary elements,
principally helium and lead. That is, as you see, a theory of
transformation of atoms which are not stable, as was believed
before, but may undergo spontaneous changes.
Radium is not alone in having these properties. Many having other
radio-elements are known already, the polonium, the mesothorium, the
radiothorium, the actinium. We know also radioactive gases, named
emanations. There is a great variety of substances and effects in
radioactivity. There is always a vast field left to experimentation
and I hope that we may have some beautiful progress in the following
years. It is my earnest desire that some of you should carry on this
scientific work and keep for your ambition the determination to make
a permanent contribution to science.
Marie Curie Speech
Discovery of Radium