i9°s ] SMITH— COLUMBIUM AND TANTALUM. 153 



by a known amount of titanium, has been regarded by most 

 analysts as entirely satisfactory. For the determination of the 

 amount of titanium in columbium many methods have been pro- 

 posed, but this is not the place to discuss them or their value. 



As late as 1877, in the last paper published by Hermann, he an- 

 nounced the element neptunium and claimed to have obtained it 

 from the acid mother liquors remaining after tantalum potassium 

 fluoride, ilmenium potassium fluoride and columbium potassium 

 fluoride had been crystallized out. The particular mineral in 

 which he observed it was a columbite from Haddam, Conn.; in 

 other words, the same mineral in which columbium had been orig- 

 inally discovered by Hatchett. 



The existence of neptunium has never been contradicted. This 

 is probably because the majority of chemists thought that the ver- 

 dict in regard to the constitution of tantalites and columbites had 

 been given by Marignac, and that the numerous, unusual reactions 

 of the metallic acids contained in those minerals, noted and com- 

 mented upon at various times by Heinrich Rose, von Kobell, 

 Blomstrand and Hermann, were all due to the contaminating 

 influence of titanium. 



The two elements, columbium and tantalum, in their derivatives, 

 have received comparatively little attention within the last quarter 

 of a century, although at intervals attempts have been made to 

 clear up the mystery which, in a certain sense, surrounds them. 

 In this laboratory, several investigations upon derivatives of them 

 have been made. These being not wholly satisfactory, about three 

 years ago, 50 lbs. of columbite from South Dakota and 25 lbs. 

 from Haddam, Conn., were worked up, with a view of getting an 

 abundant supply of starting-out material ; with the view, also, of 

 studying anew the various derivatives of both columbium and tan- 

 talum. In the year 1903-1904, Dr. R. D. Hall devoted, in this 

 laboratory, much time and labor to the double fluorides of tantalum 

 and columbium. He made a comparative study of the reactions of 

 the same with the reactions of titanium. His results have been 

 published, but from an examination of them it will be observed 

 that he was not able to find any tests, while using the double fluor- 

 ides, which differentiated titanium from columbium so thoroughly 

 that he could expect to obtain a complete separation of these two 

 most interesting elements. It is true that he was able, by precipi- 



