TELLURIC ACID. (J25 



Bitellurite of potash, KO, Te 2 O 4 , is obtained by fusing two 

 atoms of tellurous acid with one atom of carbonate of potash. 

 It appears to be capable of existing in a hot solution, and of 

 crystallizing in certain circumstances ; but it is decomposed by 

 cold water, which resolves it into the neutral salt, which dis- 

 solves, and a quadritellurite of potash, KO, Te 4 O 8 + 4HO. The 

 latter salt cannot be redissolved again in water, without decom- 

 position. In losing its water when heated, it swells up like borax. 



Telluric acid, TeO 3 ; 1101.8 or 88.25. This acid is obtained 

 in combination with potash, on fusing tellurous acid with nitre. 

 It may then be transferred to barytes, and the insoluble tellu- 

 rate of barytes decomposed by sulphuric acid. The solution of 

 telluric acid gives bulky hexagonal prismatic crystals. Its 

 taste is not acid, but metallic, resembling that of nitrate of 

 silver. Indeed, it appears to be a feeble acid, reddening litmus 

 paper, although with difficulty, when the solution is diluted. 

 The crystallized acid contains 3 HO, of which it loses 2HO by 

 efflorescence, a little above 212. It thereafter appears insoluble 

 in cold water, but may be redissolved completely by long diges- 

 tion, particularly with ebullition, and is not permanently altered. 

 Telluric affects the same multiples in its salts as tellurous acid. 

 The neutral tellurate of potash is KO,TeO 3 + 5HO, bitellarate 

 of potash, KO, Te 2 O 6 +4HO, quadritellurate of potash, 

 KO,Te 4 O 12 + 4HO. All these salts may be obtained directly, 

 in the humid way, by dissolving the proper proportions of 

 hydrated acid and carbonate of potash together, in hot water. 

 A portion of the combined water, in the last two salts, is un- 

 questionably basic, but how much of it is so has not been deter- 

 mined. They cannot be made anhydrous by heat without being 

 essentially altered in properties. 



Alphatelluric acid. The crystals of hydrated telluric acid 

 lose all their water at a heat under redness, and become a mass 

 of a fine orange yellow colour, without changing their form. 

 This yellow matter, which is distinguished as alphatelluric acid 

 by Berzelius, is remarkable for its indifference to chemical 

 reagents, being completely insoluble in cold or boiling water, in 

 hot hydrochloric and nitric acids, and in potash ley. At a high 

 temperature it is decomposed, losing oxygen, and leaving tellu- 

 rous acid white and pulverulent. The salts of telluric acid are 

 also converted into tellurites, at a red heat, by the loss of 

 oxygen. 



s s 2 



