644 Original Articles. : [Oct., 
I - Cl yy IE a BU) ee OMI) 
Au — Ag 296°5 — 108 = SIBOR 
Ag — Na 108 — 23 = ib 
Cs - K 133 — 389 = 94 
Te -—- § 129 — 82 = 97 
W — Mo 18st — 96 = 8&8 
V — Cr 137 — 52°5 = 84:5 
Hg — Cd 200 112 = 88 
Cd =) Me 112 =) oe =e 
Ba — Ca 137 — 40 = 97 
Bi — Sb 210 — 122 =. 88 
Sb  -—- P 122 ol = 91 
U —- Al 120 27°53 = 92-5 
Pb — Sn 207 — 118°5 = 88:5 
Sn — Si 118°5 — 28 = 90%5 
Ta - Ti 1388 — 50 = 88 
Pt — Ro 197 — 104 = 93 
Os — Pd 199 — 106°5 = 925 
In about one-half- of the above instances, the two elements 
associated with one another, are known to be the first and third terms 
respectively of certain triplet families; and the discovery of inter- 
mediate elements in the case of some or all of the other pairs, is not 
by any means improbable. Consequent upon the existence of these 
triplet groups, we have a considerable number of pairs of elements, 
also including more than one-half the entire number of elements, 
in which the average difference of atomic weight is about half as 
great as the average difference between the previously cited pairs, 
thus :— 
I - Br or 127 — 80 — ei or 48 
Br —- Cl 80 — 385°5 = 44-5 44 
Cs — Rb 133 — 85 = 48 48 
Rb - K oe) ce BY) =) 946 48? 
Te - Se 129 — 80 = ol 48 
Se - § 80 — 32 — es 48 
Wopocan" Vv 184 — 137 = 48 48 
Vv —- Mo 13 = 96 =. 4 40 
Mo —- Cr 965 = 75255 = 48:5 44 
Cd — Zn 2 — 65 = Ai 48 
Zn — Mg 65 — 24 = alll 40 
Ba — & 137 — 87:5 = 49°5 48 
Sr — Ca 87°5 — 40 a OS 48 
Sb —- As 122 — 75 = 47 48 
AS i (HS Bil = 44 44 
Ta = Zr 138 — 89:5 = 48°56 48 
Ti 89°5 — 50 = ods) 40 
At present there seems no reason to anticipate the existence of an 
intermediate term between any one of these pairs of elements. 
In ten instances we find that more or less analogous elements 
have a difference in atomic weight of 16, or something approximating 
