perimenters found that one gramme of active barium chloride emits about fourteen small calories per hour. The specimen contained only about one sixth its weight of radium chloride, but on testing 0.08 gramme of purer material they obtained identical results, from which it can be calculated that one gramme of radium would emit 100 small calories per hour, or one atom-gramme (225 grammes) would emit each hour 22,500 calories, an amount comparable with the heat disengaged by the combustion in oxygen of one atom-gramme of hydrogen.
The continuous emission of such a large quantity of heat can not be explained by any chemical action, and must be due to some modification of the atom itself; if so, such a change must be very slow. As a matter of fact, Demarçay observed no change in the spectrum of radium examined at intervals of five months.
An English writer, commenting on the figures given by M. Curie, says that a radium salt in a pure state would melt more than its own weight of ice every hour; and half a pound of radium salt would evolve in one hour an amount of heat equal to that produced by burning one third of a cubic foot of hydrogen gas. And the extraordinary part of this is that the evolution of heat goes on without combustion, without chemical change of any kind, without alteration of its molecular structure, and continuously, leaving the salt at the end of months of activity just as potent as in the beginning. Yet this state of things must have a cause, for it must not be imagined that perpetual motion has been at last attained.
Persons who are not practically familiar with the work carried on in the laboratories of physics and chemistry are in danger of drawing unwarrantable conclusions from the statements made by imaginative reporters in the daily press, and of concluding that radium will eventually replace gas for illuminating purposes as well as anthracite for heating. Such persons do not realize the great scarcity of the raw material yielding this substance, nor the exceedingly minute quantities used in the experiments which have furnished these astounding results. A tea spoon would probably hold all the pure radium as yet prepared, and its price would amount to thousands of dollars.
And what may be expected from future researches? Do the other rare bodies, polonium, actinium and thorium, that behave in many respects like radium, also share its most recently discovered power of emitting heat? Will not scientists be compelled to revise some of the theories of physics that they regard at present as cardinal? And what are the conditions in the earth beneath our feet, when inert matter manifests energy to such an amazing extent without a known cause? The future opened to students and to philosophers is fraught with mysteries, the solution of which will be eagerly awaited by the rest of the world.
