INAUGURAL ADDRESS. H 



atoms. Or, if it was thought (as some certainly did think) that 

 the process of ionisation is preceded or accompanied by the forma- 

 tion of complexes in which solvent molecules play a part, there 

 were then no quantitative data by which this idea could be tested, 

 and it was best to set it aside till the main question of ionisation 

 itself could be settled. That having been done, however, by 

 chemical and electrical investigations which leave no room for 

 doubt, it is natural, and altogether satisfactory to find experi- 

 menters reopening the older question in its newer form, and gradu- 

 ally accumulating evidence that the ions themselves do contain 

 solvent molecules as well as those material and electrical atoms 

 of which I have spoken. Satisfactory, I say, for since the same 

 solid dissolves well in one liquid and badly in another, and the 

 same liquid acts as a good solvent to one solid and a bad one to 

 another, it is obvious on the face of it that we have to deal at the 

 outset with specific affinities, or, in other words, that some chemical 

 ■combination does occur between solvent and solute. The theory 

 of this " hydration of the ions " is still very incomplete, but our 

 interest in it is increasing. It must, however, be pointed out that 

 it supplements, but in no way contradicts, the ionic theory as 

 originally set out by Arrhenius. 



From a totally different line of experimental work, ionic ideas 

 have received verification that was certainly not looked for by 

 chemists. I refer to the brilliant series of researches on the con- 

 duction of electricity through gases at low pressures which we 

 associate chiefly with the names of Crookes, Lenard, Rontgen, and 

 Sir J. J. Thomson and his school at the Cambridge Cavendish 

 Laboratory. For the outcome of this is the proof that electrical 

 atoms, of the same magnitude as that deduced from the study of 

 solutions, can exist in so-called vacuum tubes, either combined 

 with material atoms in the form of gaseous ions or actually moving 

 in the free state. And we have even definite information about 

 the distinguishing characteristics of the negative and the positive 

 electrical atoms and about their masses relatively to the material 

 atoms of the chemist. The negative electrical atom — or, to use its 

 proper name, the " electron " — is of the order one-thousandth of 

 the mass of the hydrogen atom, while the positive one is a much 

 bigger entity, and possibly has no real existence apart from matter. 

 Work in this direction and in the allied field of radio-activity (to 

 which I shall refer again) has not only established beyond dispute 

 the existence of ions and electrons, but opened up the most far- 

 reaching enquiries and speculations as to the constitution and 

 true relations of ions, electrons, and material atoms. 



