Multiple Proportions of the Atomic Weights. 81 



shown in his table, is equivalent to renouncing the idea of 

 periodicity altogether. 



In the conflict between the distinct ideas of periodicity, 

 and the arrangement of the elements in natural groups, 

 Mendeleeffhas found himself in the same dilemma as New- 

 lands in having to decide whether an element should be placed 

 at the head or bottom of a series. This will be seen in 

 Mendeleeff's table where he places copper, silver, and gold 

 in both the first and eighth groups, and he has not ventured 

 to state in his memoir to which of the groups these 

 elements belong. No philosophical chemist would admit 

 Au in the first group as the analogue of Ag and Cu ; and 

 the latter elements are equally inadmissible in the eighth 

 group as analogues of iron and palladium. Moreover, the 

 relation of gold to the platinum metals is too well estab- 

 lished to permit of its separation from them, and the 

 exclusion of gold from the first group would leave a place 

 unoccupied by any element of high atomic weight in which 

 Hg falls naturally as the analogue of Ag and Cu in my 

 table, as well as in that of Roscoe and Schorlemmer. 



Besides attributing in his table an excessive atomic 

 weight to gold, Mendeleeff has reversed the well-established 

 order of the atomic weights of the platinum metals, notwith- 

 standing that their specific gravities are in accordance with 

 the law which correlates these properties of the elements. 



The requirements of the assumed periodic law also 

 necessitate the anomalous grouping of boron with alumin- 

 ium ; mercury with zinc ; and the separation of iron from 

 manganese ; the latter standing alone as a metallic element 

 in group VII. Excepting manganese, this group consists 

 of monatomic halogens only ; while the intensely negative 

 elements of the oxygen series have no analogues in group 

 VI., either in their chemical or physical relations. The 

 atomic weight of tellurium = 125 in this group has also 

 been reduced abnormally to make it fall into the system. 



