MancJicstcr ]\Iei)ioiys, Vol. Hi. (1907), No. \. 3 



Taking the instance of radium chloride, I have 

 estimated its combining weight after the classical method 

 of Marignac^ and Dumas'' in their experimental deter- 

 mination of the atomic weight of barium as follows : — 



1. One part of silver corresponds to viy^ parts of 



radium chloride, or -. 



1-176 



2. The atomic weight of silver being 108, we have 



radium chloride = v\'j6 x 108 = 127 minus 

 CI (35) = 92 the combining weight of radium 

 with chlorine. 



3. Now 2x92=184 is the bivalent atomic weight of 



radium with bivalent oxygen in the positive 

 and negative series H2n, as shown in my 

 general Table, with a possible increase of one 

 unit in the experimental determination, as in 

 the instance of barium (136 — 137). 



I have previously shown that the positive series of 

 elements H2n closes with lead (208), and that if any 

 higher member of the series of alkaline-earth metals 

 exist, it would have an atomic weight of 232, and an 

 approximate specific gravity of ']:' 



Assuming this hypothetical member to be radium, 

 the combining equivalent of its chloride with silver 

 (CI 35 and Ag 108) would be i"399 in accordance with 

 the determinations arrived at with the other members of 

 the same series, and not r37i as determined experi- 

 mentally^for the intermediate atomic weight 226, recently 

 assigned to radium.* 



1 Bibl. Univ. Archives, 1858, p. 81. 

 ^ Ann. Ckiin. Fhys., vol. 55, p. 139, 1859. 

 ' Manchester Memoirs, vol. 51, No. 2, 1906. 

 ^ Coinptcs rendiis, vol. 145, p. 422, 1907. 



