I9 o S .J HALL AND SMITH— C0LUMB1UM. 1 ( J5 



excess of the reagent to form columbates. This class while show- 

 ing pronounced difference of behavior is useless as a means of 

 separation, for upon treating a solution containing both titanium 

 and columbium with one of these reagents the titanium was found 

 both in the soluble and in the insoluble portion. Columbium was 

 also found in the titanium precipitate. The probable explanation 

 for this is that a columbate was formed which dissolved the freshly 

 precipitated titanium hydrate to a salt of a complex titanoso- 

 columbic acid, which was soluble, and also a small amount of an 

 acid salt or a free acid containing an excess of titanium, which was 

 insoluble. 



2. To the second class of reagents belong those which precipi- 

 tate the hydrates of the two elements and are not sufficiently basic 

 to dissolve the columbium hydrate and form columbates. Those 

 reagents which are sufficiently basic to completely precipitate the 

 columbium are strong enough to partially precipitate the titanium. 

 Quinoline seemed the most promising of all the reagents which were 

 tried. 



3. Those reagents which gave only a partial precipitation with 

 columbium and no precipitation with titanium solutions did not 

 precipitate columbium hydrate free from titanium, from a solution 

 containing both titanium and columbium. The hydrate pre- 

 cipitated always gave a strong test for titanium after dissolving it 

 in oxalic acid. This may have been due in part to the extreme 

 difficulty encountered in washing the precipitate free from mother 

 liquor. 



4. The remaining reagents precipitated neither titanium nor 

 columbium. 



REACTIONS OF THE DOUBLE FLUORIDES OF COLUMBIUM, TITANIUM, 



TANTALUM, TIN AND TUNGSTEN WITH VARIOUS REAGENTS IN 



CONCENTRATED SULPHURIC ACID. 



A small amount of the reagent was dissolved in eight to ten 

 drops of concentrated sulphuric acid on a glazed porcelain sur- 

 face and the crystalline double fluoride introduced into this acid 

 solution. In most cases the color was destroyed upon diluting 

 with water. No color was imparted to tin solutions by any of the 

 reagents which appear below. 



