394 



properties of llio cleiueiils, since almost all iinpoi'taiit plivsical pro- 

 perties are periodic functions of their atomic weights. 



By plottino' Dhwars's vahies of specific heat at about 50° absolute, 

 we get a distinct periodic curve ; evidently at about 50° absolute, 



V-'" 



> Atomic weights of elements 



Fig. 4. 



hpccilic heat, like other pijysical properties of elements, is a periodic 

 function of the atomic weight of the elements. The alkali metals, 

 lilliinm, sodium, potassium, rubidium, caesium etc. lie on a straight 

 line at the top of the curve. The halogen elements lie on a straight 

 line on the ascending portion of the curve near the alkali metals, 

 on the descending portion nearing the alkali metals lie Mg, Ca, Sr 

 etc. S, Se and Te may be connected by a straight line. So also Zn, 

 Cd and Hg. The platinum metals, (Osmium, iridium, platinum, 

 ruthenium, rhodium, and ])alladium) lie on tiie minima of the curves. 



Coefficient of Ilnenv expansion. The researches of Fize.4U show 

 that the volatile elements occurring in the ascending curve possess, 

 almost without exception, a larger coefficient of expansion by heat 

 Itetween 0° and 100° than the not easily fusible elements occupying 

 the Diinimum of Loth.vk Mkykk's curve. 



Similar vague suggestions are collected in Lotiiar Mkyer's "Theories 

 of Chemistry" Eng. Trans, p. J 31 from the works of Carnelly 

 {.lourn. Chem. Soc. J879, 565); Wiebk (Ber. 1878, 2289; 1880, 

 1258); Raoul PicTKT (Compt. rend. 1879 r.XXXVIIl, 855) on the 



