OF ARTS AND SCIENCES: MAY 24, 1864. 813 



chemistry; others, of a more general nature, and extending in series 

 through one or more volumes of the Annals, are researches upon the 

 composition of, or the reactions which characterize, different groups of 

 chemical compounds. So various, indeed, are these subjects, that there 

 is hardly an element for some portion of our knowledge of which we 

 are not indebted to Heinrich Rose. It is therefore impossible to give 

 an analysis of works whose mere titles would require more space than 

 is allotted by custom to the memory of our distinguished associates. 

 Much of what was afterwards arranged in its proper place in his 

 Analytical Chemistry, appeared originally as contributions to the 

 Annals. 



The most remarkable of these papers is a series which extends, with 

 interruptions, through more than fifteen years, and contains the history 

 of his discovery of the metal Niobium. The points of interest of this 

 investigation are obscured by its great detail, and by the repetitions, 

 and sometimes inconsistencies, inevitable in a work prosecuted at long 

 intervals. From the different specific gravities of the several varieties 

 of the mineral called Tantalite, as well as of the metallic acids contained 

 in them. Rose was led to believe that these acids were the oxides of 

 different metals. He at first assumed the existence of two new metals, 

 which he called Niobium and Pelopium, and which, by uniting with 

 oxygen, gave rise to the niobic and pelopic acids. Further examina- 

 tion showed, however, that these acids contained but one metal, which 

 was combined in them with different proportions of oxygen. But the 

 one of these acids could in no way be directly converted into the other ; 

 they comported in so many respects like the oxides of two similar but 

 different metals, that for a long time he so regarded them. The metal 

 obtained from these acids is the same, whether the one or the other of 

 them has been employed ; but when the metal is again oxidized, there 

 is formed always the one, never the other, of the two acids. When the 

 metal from either of the acids is made to combine with sulphur, which 

 it does in several proportions, and the resulting sulphuret is reconverted 

 by oxidation into acid, the acid is invariably the same as that from 

 which the sulphuret was formed. " This is a phenomenon," says Rose, 

 " to which there is no analogy in chemistry. For the two acids act, 

 not like the oxides of one and the same metal, but like oxides of two 

 different metals. The tendency to the formation of the one or the other 

 of the acids must have existed beforehand in the metal itself. The 

 inquiry had touched upon ground which is as yet hidden ft-om us by 



