A NEW SOURCE OF HEAT: RADIUM. 63 



perimentcrs 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 disen- 

 gaged 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 modifi- 

 cation of the atom itself; if so, such a change must be very slow. As 

 a matter of fact, Demargay 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, with- 

 out 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 eventu- 

 ally 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. 



