86 CHEMICAL PHYSICS. 



state of stability or equilibrium, in which state they cannot be sepa- 

 rated by our ordinary chemical operations, and thus appear as single 

 units or atoms. In radium and in other radio-active bodies these 

 complexes of corpuscles are in unstable equilibrium and possess 

 potential energy which has a tendency to diminish in quantity, thus 

 causing the state of unrest exhibited by radio-active bodies. The 

 potential energy becomes kinetic in the form of heat, light, etc., and 

 meantime the complexes are transformed to stable forms which do not 

 possess radio-activity and which act like the chemical atoms. 



This would involve the transformation of one element into a new 

 element. And that is exactly what has been found to take place in 

 the case of radium, namely, that the emanation from radium contains 

 helium. (For the manufacture of radium compounds, see the article 

 on Radium.) 



QUESTIONS. Name some conductors and non-conductors of electricity, and 

 explain their behavior in connection with electrical phenomena. What is 

 meant by positive and negative, and by static and current electricity ? Describe 

 three methods for generating electricity. Name the three principal units used 

 in the measurement of electrical currents, and explain the methods employed. 

 Explain the construction and action of a galvanic cell. What is a permanent 

 magnet, and what is an electromagnet ? How are they made, and what are their 

 characteristic properties? Define the following terms: Anode, cathode, circuit, 

 electric current, induction, and electromotive force. Describe construction of 

 the electric furnace, and explain its action. How may electricity be used in 

 the generation of heat, light, mechanical motion, and chemical action? 



