THE DISTRIBUTION OF CHEMICAL 



ELEMENTS 



By INGO W. D. HACKH, 



Professor of Chemistry, College of Physicians and Surgeons, San Francisco, Cal., U.S.A. 



Science has reached another milestone on its road toward an 

 understanding of nature. This mark is the completion or near 

 completion of the system of matter as expressed in the periodic 

 law of the chemical elements. Perhaps no other natural law, 

 save some astronomical laws, has been so fully established. 

 From its early conception about fifty years ago by Newlands, 1 

 MendeleefiV and Lothar Meyer, 3 it has had various fortunes, 

 enthusiastically supported by some, and despised by others 4 

 on account of its fragmentary nature. There have been three 

 great discoveries of recent decades which have helped to perfect 

 the system and eliminate the many gaps appearing in the 

 original table. 



The discovery of the rare gases of the atmosphere 6 revealed 

 a group of elements which are entirely inert and enter into no 

 chemical combination. After several years of discussion they 

 were finally placed into a zero-group of the periodic system. 6 

 In this position they revealed themselves as a missing link 

 between a strongly negative halogen and a strongly positive 

 alkalimetal, for their electro potential is assumed to be ± cc « 

 Thus a continuous line or series of the elements was formed 

 when they were arranged according to increasing atomic weight. 



The discovery of the radio-active elements 7 established 



1 Chem. News, 1864, vol. x, pp. 59, 94 ; 1866, vol. xiii, pp. 113, 130. 



2 Journ. Russ. Chem. Ges., 1869, vol. i, pp. 60, 229 ; Ber. ii, p. 553, 1869. 



3 Ann. Chem. Pharm., 1870, vol. vii, p. 354. 



4 E.g. Ostwald, Lehrbitch, 2 Aufl., Bd. 1, pp. 137 and 11 17 ; Wyrouboff, 

 Chem. News, 1896, vol. lxxiv, p. 31 ; Wilde, Compt. Rend., 1898, vol. cxxvii, 

 p. 613. 



5 Ramsay, Rayleigh, Travers, Cleve, and others. 



6 Thomson, Zeit. Anorg. Chem., 1895, vol. ix, pp. 190, 283 ; Deeley, Chem. 

 News, 1895, vol. lxxii, p. 297 ; Wilde, Chem. News, 1895, vol. lxxii, p. 317 ; 

 1896, vol. lxxiii, p. 35 ; Sperber, Zeit. Anorg. Chem., 1897, vol. xiv, p. 164 ; 

 Chem. News, vol. lxxvii, p. 87 ; Ramsay, Ber., 1898, vol. xxxi, p. 3111 ; 

 Crookes, Zeit. Anorg. Chem., 1898, vol. xviii, p. 72 ; Howe, Chem. News, 1899, 

 vol. lxxx, p. 74. 



7 Curie, Schmidt, Debierne, Rutherford, Soddy, Marckwald, Fajans. 



602 



