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CHAP. XIIL " FRACTIONATION " EVIDENCE. 



IN the three previous chapters I have endeavoured to show that new 

 methods of inquiry in the physical field all support the dissociation 

 hypothesis. I have next to show that similar confirmation may be 

 expected when the present ineffective chemical methods of analysis and 

 determination are replaced by more stringent ones, such as those exem- 

 plified and foreshadowed by Sir William Crookes's patient fractionation 

 work on yttria. 



For the first definite chemical confirmation of my work I had to 

 wait till 1883. In that year Sir William Crookes gave an account, in 

 a Bakerian Lecture to the Royal Society, of his beautiful researches 

 on yttria. In the lecture he gave a sketch of the train of reasoning by 

 which he had been led to the opinion that systematic fractionation had 

 split up this stable molecular group into its " constituents," and these 

 were not yttrium and oxygen, as they should have been. 



Subsequently in an address to the British Association at the Bir- 

 mingham meeting in 1886, he gave an account of the method of frac- 

 tionation which had led to these results. 



The importance of the work on yttria in relation to the question of 

 dissociation lies in the fact that by the variation in intensity of the 

 various lines of the phosphorescence spectrum of yttria, Sir William 

 Crookes was led to the view that more elements than one were in 

 question that the ordinary chemical processes had been quite unable 

 to make anything but an element out of a mixture. As a result of his 

 work he found five components "by a veritable splitting up of the 

 yttrium molecule." This obviously strengthens the view that if our 

 chemical resources were much greater than they are, the demonstration 

 that other similar changes of intensity in the spectra of other elements 

 would also be achieved. 



I now quote Sir William Crookes on his method, which constitutes 

 a veritable new engine of chemical research. 



" Broadly speaking, the operation consists in fixing upon some 

 chemical reaction in which there is the most likelihood of a difference 

 in the behaviour of the elements under treatment, and performing it 

 in an incomplete manner, so that only a certain fraction of the total 

 bases present is separated : the object being to get part of the material 



