PHYSICAL SCIENCE IN THE NINETEENTH CENTURY 365 



amounts set free at the electrodes are proportional to their 

 chemical equivalents. To him the name electrolysis is due. A 

 closer study of the phenomena of electrolysis led Clausius to the 

 hypothesis that the molecules of salts, acids, and bases, pre- 

 viously regarded as disintegrated only by the passage of the 

 electric current, are already dissociated in ordinary solutions. 

 To these electrically charged part-molecules Faraday gave the 

 name ions. Arrhenius proved that salts in dilute solution are 

 dissociated into then* ions almost completely, instead of only 

 very slightly as Clausius supposed. This theory of Arrhenius, 

 known as the Theory of Electrolytic Dissociation, of which an 

 account would be too technical for the present purpose, co- 

 ordinates and correlates heterogeneous masses of chemical facts, 

 which apparently bore little or no relation to one another, and 

 refers them to a common cause. 



During the latter part of the nineteenth century a study of the 

 rate and equilibrium conditions of chemical reactions led by de- 

 grees to the formulation of the so-called law of mass action and to 

 many important thermodynamic relations. Chemistry thus came 

 to share with physics the possibility of utilizing the calculus, 

 becoming thereby more fully a quantitative science. 



REFERENCES FOR READING 



MERZ, J. T. History of European Thought in the Nineteenth Century. 



POINCARE, H. Science and Hypothesis. 



RAMSAY, WILLIAM. The Gases of the Atmosphere and the History of Their 



Discovery. 



ROSCOE, H. E. John Dalton. 

 SODDY, F. Matter and Energy. 



THOMPSON, S. P. Michael Faraday: His Life and Work. 

 TILDEN, W. A. Progress of Scientific Chemistry in Our Own Time. 

 TYNDALL, JOHN. Faraday as a Discoverer. 



