Multiple Proportions of the Atomic Weights. 83 



Two of these elements in my table, Sc = 42 and Ge = 72, 

 have been discovered since my paper was published by the 

 Society. This paper is, consequently, entitled to some notice 

 in connexion with the history of these elements. I have, 

 moreover, good reason for thinking, from the multiple 

 relations of scandium to the other members of the series, 

 that my determination of its atomic weight = 42 is correct, 

 as against 44, the value given in the table of Mcndeleeff. 



I have also shown that Sc, Ga, In, Tl, are analogues of 

 the even series H3n, and form triads homologous with K, 

 Rb, Cs, in the series Hn. 



The simplicity of the spectral reactions of Tl, In, Ga,. 

 Sc, which I have recently investigated and compared,* con- 

 firm the positions of these elements in relation to their 

 homologues in Hn. Mendeleeff has, however, placed Ga in 

 the uneven series (Gruppe III.), homologous in position with 

 Cu, Zn, and made Sc the analogue of Y; also, In, homologous 

 with Ag Cd — positions which will not be admitted by philo- 

 sophical chemists — and his atomic weight of gallium = 68, 

 as I have shown, is still open to revision, and will be found 

 ultimately to be =96, as in my table. 



A peculiar feature of the chemical philosophy of 

 Mendeleeff is his intolerant rejection of all theories of 

 the nature of the elements, and his entire ignorement of the 

 multiple relations subsisting among them.-f- 



* Proc. Roy. Soc, vol. 53, 1893. 



+ Faraday Lecture delivered before the Fellows of the Chemical Society in 

 the Royal Institution, June 4th, 1889. Chetn. Soc. foumaZ, Vol. LVL, 

 pp. 634 — 656, 1889. J rans actions, 1889. The utterances of the Russian 

 chemist on this occasion are in striking contrast to the thoughtful opinions 

 expressed by Faraday in the same Institution in a course of six lectures delivered 

 in the year 1852, in which he sets forth, with admirable lucidity, the reasons, 

 for his belief in the compound nature of certain groups of elements. He 

 showed at the same time the multiple relations involved in the triads of 

 Dumas, who, as is well known, shared the views of Faraday on the nature of 

 the elements. 



