Bayley — On the Development of Chemical Elements. 793 



XCVII. SUSGESTIONS OK THE DEVELOPMENT OF THE CyCIIC LaAV OF 



THE Chemicai Elements. By Thomas Batlet, Assoc. K.C.Sc.I. 

 (Plate XXI.) 



[Eead, February 26, 1883.] 



In a paper published in the Philosophical Magazine, Jan., 1882, in 

 discussing the law, originated by JSCewlands, and called by him the law 

 of octaves, and subsequently developed by Mendelejeff and L. Meyer 

 under the name of the periodic law, the author pointed out that '' the 

 increments of atomic weight which, starting from hydrogen, succes- 

 sively give the points where the atomic volume is a minimum are 

 members of the geometric series (see note, p. 795) : 



a, a y. h, a x h^, a x h^ . . . a x h^, 



where a = 10, and i ~ — ." 

 6 



In the same Paper it was shown that the colour properties of the 

 elements when associated as bases with colourless acids are periodic, the 

 metals in the first and second cycles forming no coloured solutions, and 

 in succeeding cycles those metals only forming coloured solutions which 

 occupy the region of low atomic volume. In accordance with this fact, 

 it was argued that uranium, which is a metal having strongly coloured 

 solutions, a high melting point, and great density, must occupy the 

 mediate position in a cycle, and the atomic weight, 180, was suggested 

 as probable because agreeing with these conditions. Since the Paper 

 was written, however, investigation of the density of uranium tetra- 

 chloride and tetrabromide by Zimmennann has shown that the atomic 

 weight of uranium cannot be less than 240, and other researches — that 

 of Setterberg on caesium and that of I^ilson on thorinum in particular 

 — have afforded material for the further development of the cyclic law. 



The successive terms of the geometric series 



«, a X h, ax h^, a x h^ . . . a x 5,„ 



where «5 = 10 and i = -r-, are 

 6 



10, 16-6, 27-5, 45-7, 75-9, 126-0, 

 and the atomic weights are 



11, 27-6, 55-1, 100-8, 176-7, 302-7. 



It is therefore probable that the sixth cycle attains to its minimum 

 of atomic volume in the neighbourhood of the atomic weight 300. The 

 progression of atomic weight in the first two cycles is 1 G, and in the 

 second and third approximately Ihi-ee times sixteen, or 46-4 and 47-5 



