143 



M. Caron on Tin Ore containing Niobium. 



Percentage 



Speci 



fie gravity of aqueous alcohol * 



of alcohol 

 by weight. 











at0°. 



at 10°. 



at 20°. 



at 30°. 







99988 



99975 



99831 



99579 



5 



99135 



99113 



98945 



98680 



10 



98493 



98409 



98195 



97892 



15 



97995 



97816 



97527 



97142 



20 



97566 



97263 



96877 



96413 



25 



95115 



96672 



96185 



95628 



30 



96540 



95998 



95403 



94751 



35 



95784 



95174 



94514 



93813 



40 



94939 



94255 



93511 



92787 



45 



93977 



93254 



92493 



91710 



50 



92940 



92182 



91400 



90577 



55 



91848 



91074 



90275 



89456 



60 



90742 



89944 



89129 



88304 



65 



89595 



88790 



87961 



87125 



70 



88420 



87613 



86781 



85925 



75 



87215 



86427 



85580 



84719 



80 



86035 



82515 



84366 



83483 



85 



84789 



83967 



83115 



82232 



90 



83482 



82665 



81801 



80918 



95 



82119 



81291 



80433 



79553 



100 



80625 



79788 



78945 



78096 



Caronf has discovered the existence of niobium and tantalum 

 in a tin ore found at Montebras, which is now being there worked 

 as a source of tin. The quantity amounts to about 2 or 3 per 

 cent., though in some cases as much as 5 per cent, has been ex- 

 tracted. Of two methods which he describes of extracting the 

 niobium, the following is recommended as the best, though 

 not the most expeditious. 



The mineral, deprived of gangue and levigated, is fused with a 

 mixture of charcoal and carbonate of soda, by which means a 

 button of tin is obtained, the niobium being contained in the 

 slag. This slag is then treated with a small quantity of hydro- 

 chloric acid, which removes the soda and a considerable portion 

 of unreduced tin. The residue, consisting of silica, oxides of tin, 

 niobium, manganese, iron, &c, is dissolved in a mixture of fluoric 

 and sulphuric acids, diluted with water, filtered, and evaporated 

 so as to expel the major part of the fluosilicic acid; it is then 

 mixed with a large quantity of water and boiled, by which all the 

 niobic acid of the liquid is precipitated. This precipitate of 

 niobic acid is far from being pure ; it contains much tin, a little 

 iron, manganese, and perhaps tungsten. A prolonged digestion 

 with hydrosulphate of ammonia removes the tin and the tung- 



* Water at 4°= 100000. 



t Comptes Rendus, December 11, 1865. 



