TANTALIC ACID. 6*47 



tantalite and yttrotantalite. Their metal was fully studied by 

 Berzelius; and columbium, which had been imperfectly ex- 

 amined by Hatchett, was found by Dr. Wollaston, in 1809, to 

 be the same metal. Tantalum has since been observed in two 

 or three other minerals, but all of them among the rarest 

 species. 



Tantalum is not reduced by carbon, but Berzelius obtained 

 it by decomposing the double fluoride of silicon and potassium 

 by potassium. It was a black powder, which could be washed 

 and dried, and assumed an iron grey metallic lustre under the 

 burnisher. It took fire in air below a red heat and burned 

 with much vivacity, yielding tantalic acid. No acid has a sen- 

 sible action upon tantalum except hydrofluoric acid. Tantalum 

 combines with oxygen in two proportions, forming tantalic 

 oxide, Ta O 2 , and tantalic acid, Ta O 3 . 



Tantalic oxide, Ta O 2 , 2507.4 or 200.9. This oxide is ob- 

 tained on exposing tantalic acid in a charcoal crucible to the 

 heat of a wind furnace, for an hour and a half. With the ex- 

 ception of the external film immediately in contact with the 

 charcoal, which is metallic tantalum, the mass of acid is con- 

 verted into tantalic oxide. This oxide is of a dark grey colour, 

 its particles are so hard as to scratch glass ; it is soluble in no 

 acid, not even in aqua regia or hydrofluoric mixed with nitric 

 acid. The name tantalum was applied to the metal by Ekeberg, 

 on account of this insolubility of its oxide in acids, in allusion 

 to the fable of Tantalus. Heated to low redness in air, it burns 

 slowly, and is converted, although not entirely, into tantalic 

 acid. 



Tantalic acid, Ta O 3 , 2607-4 or 208.9. It is in the state of 

 tantalic acid that tantalum exists in most of its minerals, com- 

 bined with the oxides of iron and manganese in tantalite, or with 

 yttria in yttrotantalite. The acid may be obtained by fusing 

 the mineral with carbonate of potash, and decomposing the tan- 

 talate of potash formed, by an acid, and also by fusion with 

 bisulphate of potash (Berzelius, Traite, I, 392). It presents 

 itself as a white powder, which reddens litmus paper; when 

 distilled in a retort, it parts with its water, which amounts to 

 11| per cent, Ta O 3 -f 3HO, and loses the latter property. The 

 density of the ignited acid is 6.5, in this state it is attacked by 

 alkalies only. Tantalic acid dissolves by fusion in bisulphate 

 of potash, and when hydrated in binoxalate of potash by the 



