320 Mr. W. Sutherland on a New Periodic 



as Cu and Ag to the first, have periods '32 and '47, again as 

 2 to 3, and involving a fundamental constant very close to 

 that of the main family. In the next main family the only 

 members for which data are available are Al and La, for 

 which we get *20 and '56, which are nearly as 2 to 6, that is, 

 nearly as Na to Cs or Mg to Ba, as they ought to be. But 

 the subsidiary members Ga and In give '54 and *57, which 

 are not related in the same way as Cu and Ag or Zn and Cd; 

 so that here complete analogy between the families breaks 

 down when we reach the family that marks the transition to 

 the non-metallic families. The following three groups of 

 values are worth notice : — 



Mn. Fe. Co. Ni. Ru. Rh. Pd. Os. Ir. Pt. 



•16 -16 -16 -17 -21 -20 -23 -23 -25 -27 



The following values of (M/d)* M*A/T are added ; though 

 not of much use, because in many cases we know aTM^ not 

 to be near enough to '045. 



Au. Hg. TL Sn. Pb. P. As. Sb. Bi. 

 •35 -94 -65 -55 '63 -33 -36 *49 -71 



S. Se. Te. CI. Br. I. 

 •41 -50 -50 -68 -80 -75. 



' It is interesting now to pass on to the case of compounds 

 extending to them the formula p = (M/d)$M?/ s /T, taking M 

 as the ordinary molecular weight, and remembering now that 

 MC is constant only for similarly constituted molecules, being 

 proportional to the number of atoms in the molecule. Car- 

 nelley has given the melting-points of many compounds (Phil. 

 Mag. [5] xviii.). Let us consider first the compounds of the Li 

 family with the halogens ; the study of the numbers tabulated 

 below shows that the period p of any such compound is the 

 sum of two periods characteristic of each of its atoms. These 

 characteristic periods are as follows : — 



Li. Na. K. Rb. 



•075 -150 -225 -375 



F. CI. Br. I. 



•116 -232 -348 -464. 



For the lithium family these numbers run as 1, 2, 3, 5, 

 almost the same as the series for them in the free state. For 

 the halogens the numbers run as 1, 2, 3, 4. The soundness 

 of these conclusions is shown in the following Table, where 

 the values of p or (M/d)~ s M.z/\/T, obtained from experiment 



