56 president's address — section b. 



reduction of temperature would be greater. The solution of 

 a salt in water may be regarded as the removal of molecule 

 after molecule in the crystalline architecture, the whole mass 

 finally reaching one uniform state of motion — i.e., equilibrium 

 of temperature and action. The molecules thus dislodged 

 from their recent crystalline structure are free to s])in through 

 the liquid as double stars, having a diminished degree of 

 attraction for each other owing to their approximately similar 

 atomic weight. Thus it comes to pass that we have a stage 

 of incipient dissociation, a large proportion of the atoms being- 

 liberated in the free state or dissociated into their ions, — 

 a conclusion arrived at by Arrhenius in 1887, and quite 

 independently by Planck in the same year. 



The apparent decomposition of a salt solution, i.e., an 

 electrolyte into free ions, is considered by some to be a process 

 of direction and not one of real decomposition ; but I think 

 myself that it is one of oscillation between mere direction on 

 the passage of the current on the one hand, and dissociation 

 on the other. 



In the present controversy between association and dis- 

 sociation there is reason to believe the advocates of both 

 systems to be right, so far as the facts are concerned, the 

 phenomena presented by the hydration of sulphuric acid not 

 being on all fours with the facts brought to light in cases of 

 salt solution. However, the day will soon dawn when the 

 whole subject relating to chemical energy will be fully eluci- 

 dated, and means found for its precise measurement. It is 

 now a veritable mine of intellectual activity, and it is no 

 wonder that new facts are constantly being recorded. 



We may expect that, with such an array of facts such as 

 are now given to the world by Ostwald, Van't Hoff, Glad- 

 stone, Pickering, Arrhenius, Armstrong, and others — facts 

 that slip easily into their proper places in the great fabric of 

 Physical Science — that some master mind must sooner or 

 later arise who shall so co-ordinate, interpret, and arrange 

 them as to deduce therefrom the laws of chemical energy 

 and affinity. Mendelejeff, in recognising this, bids us 

 anticipate such a grand reaUsation. He says,* "the invisible 

 woi'ld of chemical atoms is still waiting for the creator of 

 chemical mechanics. For him our age is collecting a mass 

 of materials, the inductions of well-digested facts, and many- 



* An Attempt to apply to Chemistry one of the Principles of Newton's 

 Natural Philosophy : a Lectui-e delivered at the Royal Institution of Great 

 Britain, May 31, 1889. 



