RADIUM PRODUCES HEAT 49 



EXPERIMENTS FOR THE TEACHER 



Obtain a five-pound tank of carbon dioxide and a small 

 flannel bag. Tie the bag over the outlet of the tank, tipping 

 the tank so that the outlet is lower than the rest of the tank. 

 Open wide the stopcock for half a minute. If there is not 

 enough solid, repeat. Put some mercury in a test tube and 

 place the test tube in a beaker half full of ether, containing 

 the carbon dioxide. When the mercury is frozen, break the 

 test tube and drop the solid mercury on the table like any 

 common metal. 



33. RADIUM PRODUCES HEAT 



Radium was for some time one of the curiosities of the 

 chemical world. Since it produced elements different from 

 itself, it seemed to be an exception to general rules governing 

 elements. We now know that other elements act in a similar 

 manner, although not to such a marked degree. 



Radium can produce chemical changes in a covered photo- 

 graphic plate, and excite fluorescence in some substances. 

 This is accomplished by the emission of rapidly moving par- 

 ticles and by some rays which are similar to Rontgen, or 

 X-rays. The particles form a gas called helium. 



Since heat is due to the motion of the molecules, the libera- 

 tion of rapidly moving particles produces so much heat that 

 the temperature of radium is always 5 F. or 2.7 C. higher 

 than its surroundings. The amount of heat liberated by one 

 gram of radium is 100 calories per hour. Thus radium can 

 melt one and one fourth of its own weight of ice every 

 hour. It is not possible to utilize this heat for practical 

 purposes. 



