32 



SCIENCE. 



[N. S. Vol XII. No. 



that which is united with the metal through 

 the medium of one to four ammonia groups 

 is dissociated. Led by a consideration of 

 these seeming inconsistencies, Werner has 

 proposed his theory of co-ordinated groups 

 within the molecules ; a theory which seems 

 to possess at least elements of truth, even if 

 not expressing the whole truth. It is pos- 

 sible, too, that Werner's theory may ex- 

 plain some of the difftculties of the theory 

 of electrolytic dissociation, and harmonize 

 it with the hydrate theory of solution. 



The constitution is, however, not the only 

 problem of these bases. To my mind their 

 connection or rather lack of connection 

 with the periodic system is one of the most 

 inexplicable facts in chemistry. It makes 

 it apparent that while the periodic law ex- 

 presses a truth without doubt the greatest 

 generalization of modern chemistry, yet 

 even this is 'jin its present statement not 

 the whole truth. We find a marvel- 

 ously full development of these bases in 

 connection with cobalt, platinum, and 



chromium. Manganese and iron which lie 

 between chromium and cobalt form no 

 bases. The higher members of the chrom- 

 ium group, that is, molybdenum, tungsten, 

 and uranium, form no bases, while the 

 higher members of the iron series, that is, 

 ruthenium and osmium do. Of nickel, 

 which stands next to cobalt and resembles 

 it so closely, no bases are known, and yet 

 it is the lowest member of the series which 

 contains platinum. It is true that bivalent 

 cobalt forms perhaps like nickel, no bases, 

 but as trivalent cobalt forms so many bases, 

 trivalent iron would seem likely to form 

 many, instead of none. If indeed manga- 

 nese and iron are capable of forming these 

 bases, it seems strange that no one has yet 

 happened upon the proper conditions. It 

 is the consideration of a subject like that of 

 these inorganic bases, which forces upon us 

 a realization of how much there is after all 

 which we do not know about chemistry. 



We turn now to a short consideration of 

 the eighth group from a theoretical stand- 



Periodic Table By F. P. Venable — Modified. 



* Possible + Series elements. 



t Possible — series elements. 



' Eka-manganese. 



