June 29, 1900.] 



SCIENCE. 



1013 



num and iridium are considered by him 

 analogous elements, each occupying the first 

 place in the octave to which it belongs ; 

 iron, rhodium, ruthenium and gold are 

 analogous elements, each occupying the 

 seventh place in its octave; while osmium 

 is included with copper and silver as the 

 second members of their octaves. There 

 was here an easily recognized inconsistency 

 which was not cleared up till many years 

 later Seubert was led by the study of the 

 periodic law to revise the atomic weights of 

 these metals. 



In his first summing up of the principles 

 of the periodic law in 1869, Mendeleefi" con- 

 cludes that "elements which are similar as 

 regards their chemical properties have 

 atomic weights which are either of nearly 

 the same value (e." g., platinum, iridium, 

 osmium) or which increase regularly (e. g., 

 potassium, rubidium, cesium)"*. So in 

 most schemes for representing the periodic 

 system, each triplet of these elements is 

 considered as a single element, and because 

 even then they do not seem to fall into reg- 

 ular periodic arrangement, they are cast 

 out, Ishmael-like, into an anomalous eighth 

 group. This is doubtless the reason they 

 have been relatively so much neglected by 

 chemists, and possibly it is not incorrect to 

 say that the chemistry of these metals is 

 less known than that of any other group of 

 well characterized elements. Yet there are 

 certainly no nine nearly related elements 

 which present so many interesting chemical 

 problems, whose solution will so much 

 further our knowledge of chemistry in 

 general. It is the purpose of this address 

 to attract the attention of the members of 

 this Section to this group and some of its 

 many problems. 



The ordinary division of these nine 

 metals is into three groups, viz, the com- 

 mon metals, iron, cobalt, and nickel, with 

 an atomic weight of from 56 to 59 and a 



*Jour. Phys. Chem. Soc. Buss., 1 (1869), 60. 



specific gravity of 7.8 to 8.9; the lighter 

 platinum metals, ruthenium, rhodium and 

 palladium, with an atomic weight 101.5 to 

 106.5 and a specific gravity of about 12 ; 

 and the heavy platinum metals, osmium, 

 iridium and platinum, of atomic weight 

 191 to 195 and specific gravity 21.5 to 22.5. 



Of these metals, iron alone can be con- 

 sidered abundant and was the only one 

 known until the eighteenth century. The 

 ores of cobalt and nickel have been known 

 for over two centuries, but the probable 

 presence of a new metal in cobalt ore was 

 first pointed out by Brandt* in 1735, and 

 nineteen years later Cronstedt f determined 

 the existence of nickel. Both of these dis- 

 coveries were several decades after con- 

 firmed by Bergman J. 



It is, however, a curious and interesting 

 fact that a coin of Bactria § of a date more 

 than two centuries before Christ has been 

 found containing twenty per cent, of nickel 

 and hence quite similar in composition to 

 our modern ' nickels.' There seem, how- 

 ever, to be no references in ancient litera- 

 ture which would indicate that attention 

 was ever attracted by nickel or any of its 

 compounds. 



Turning to the platinum metals, the first 

 recognized mention of platinum seems to 

 be in the ' Relacion historica ' of Don An- 

 tonio de UUoa (vol. 1, lib. vi, cap. 10, p. 

 606) published first in 1748, the book being 

 an account of the French expedition of 1735 

 to the western coast of South America to 

 measure an arc of the meridian on the 

 equator. The passage reads : " In the dis- 

 trict of Choco (Columbia) which contains 

 many placer mines, are also found some, 

 the gold of which, occurring mixed with 

 other substances as metals and rocks, or 



"^Akta Beg. Soe. Sci. Upsala (1735), 33. 

 t K. Svenska Vet. ATcad. Handl. (1751), 293. 

 XOpusc. Diss. 20 (1775), 24 (1780) 13 and 14, 25 

 (1779) 31 and 33. 



§ Ann. der Phys. (Pogg.), 139, 507 (1870). 



