so-called Meta-Elements. 109 



they merely point to the possible existence of such bodies. 

 When chemists are called upon to so entirely change their old 

 views upon the constitution of the elements, surely they have 

 a right to expect the most unrefutable proofs why they should 

 do so. 



It is w r ith the purpose of examining these proofs for the 

 existence of meta-eleinents, and of seeing wdiether they are 

 valid, that this paper has been brought forward. 



What is it, then, that we are requested to believe ? It is 

 that oxides of certain metals, notably of certain rare earths, 

 are capable, by suitable methods of fractionation and differen- 

 tiation, of being split up into several other earths, all of which 

 differ from each other and from the original earth, and each 

 of which we are requested to look upon, if not as the oxide of 

 a different element, at least as something approaching to this. 

 That is, w r e are required to look upon these fractionated 

 earths as oxides of bodies which cannot be formed by the 

 union of other bodies, and which therefore should earn the 

 title of elements. 



Let us, then, take an instance of the fractionation of a single 

 earth. 



Crookes started with an earth which a few years ago w T ould 

 have been pronounced by every one to be simply yttria, that 

 is, the oxide of the element yttrium. This oxide was dissolved 

 in acid, and enough ammonia added in dilute solution to pre- 

 cipitate only half the base. The precipitate obtained was 

 treated in a similar manner, and so on for several times, the 

 precipitate being collected, dissolved in acid, half of it pre- 

 cipitated again, and so on. The filtrate obtained from the 

 first precipitation was treated in a similar manner. The 

 filtrates and precipitates between these extreme fractions were 

 also made to yield their share to the final products. In this 

 manner, after a very large number of fractional precipitations, 

 a series of earths was obtained which presumably varied gra- 

 dually in their degree of basicity as they passed from one 

 extreme fraction to the other. In this way Crookes con- 

 sidered he had separated the original yttria into nine new 

 bodies, or oxides of meta-elements, to which he provisionally 

 gave the symbols 



S y , G a , Gp, Gy, G s , G e , S$, Gz, G,,. 



In what way, then, was it proved that these nine earths were 

 different ? 



Some, but not all, of the earths of this class, when sealed 

 up in tubes in which a high degree of exhaustion has been 



Phil. Mag. S. 5. Vol. 31. No. 189. Feb. 1891. K 



