Intelligence and Miscellaneous Articles. 411 



non-volatile residue on its production, or rather on its volatilization, 

 at a high temperature. This residue consists principally of the acid 

 which may be obtained from the yellow chloride by decomposition 

 with water. 



In the preparation of the yellow chloride from the columbite of 

 Bodenmais, there is formed along with it an oxychloride, which is 

 decomposed by heat into chloride and acid, just like the tungstate 

 of the chloride of tungsten. The formation of the oxychloride can 

 be prevented by placing a long layer of charcoal in the anterior 

 portion of the glass tube, in which the mixture of acid and charcoal 

 is to be treated with chlorine. While the chlorine is passing through 

 the tube, this charcoal is first raised to a strong red heat, and then 

 the mixture. 



The acid of the yellow chloride from the Bodenmais mineral, which 

 is contained in it along with the niobic acid, I have named Pelopic 

 acid, and the metal Pelopium, from Pelops the son of Tantalus and 

 the brother of Niobe ; to point out, at the same time, by this name, 

 not only its simultaneous occurrence with the oxide of niobium, but 

 more particularly the very great resemblance of pelopic acid to the 

 tantalic acid from the Finland tantalites. This similarity is indeed 

 more perfect than exists between the combinations of any other two 

 simple metals ; it is so great, that it was only after a long-continued 

 and most minute investigation that I could decide upon publishing 

 the results I had obtained. The combinations of niobium are, on 

 the contrary, very different from those of pelopium or tantalium. 



I will here describe the most important properties by which the 

 compounds of tantalium differ from the corresponding compounds 

 of pelopium, and at the same time enumerate those of niobium. 



In its properties pelopic acid is intermediate between tantalic and 

 niobic acids, just as strontia between baryta and lime. And in the 

 same way as we are able to explain many properties of strontia, by 

 assuming it to be a mixture of the two last-mentioned earths, we 

 are able to determine a priori most of the properties of pelopic acid, 

 by admitting it to be a mixture of a large proportion of tantalic acid 

 with a small quantity of niobic acid ; and as was the case with 

 bromine, which, on its discovery, was considered to be a combi- 

 nation of chlorine and iodine, I myself was long of opinion that the 

 pelopic acid was nothing more than tantalic acid still contaminated 

 by a certain quantity of niobic acid, which I had not succeeded in 

 separating. It was only by an uninterrupted investigation of this 

 subject for several years that I became convinced of the distinctness 

 of pelopic acid. 



The chlorides of the three metals dissolve in cold concentrated sul- 

 phuric acid without any evolution of heat, but with disengagement 

 of hydrochloric acid ; but if the solution of the chloride of tantalium 

 and pelopium is boiled, it solidifies to a jelly. Water then does 

 not dissolve any of the tantalic acid, but a large quantity of the 

 pelopic acid. The solution of the chloride of niobium in sulphuric 

 acid is not rendered turbid by boiling ; it even remains clear on 

 dilution with water, but if it be now boiled, the whole of the niobic 

 acid is precipitated from the solution. 



