TELLURIUM. 117 



R. Hermann : 



Hermann made many analyses of tantalium salts to 

 which, however, he ascribea quite incomprehensible for- 

 mulas. Marignac has shown that his methods were utterly 

 inadequate to produce pure preparations. He assumes two 

 atoms of tantalium and three atoms of oxygen in the acid 

 and gives the atomic weight as 645. (O = 100.) {Erd- 

 mann's Journ.fUr Prak. Chem., 70, 1857, 193.) 



C. Marignac : 182 (0 = 16). 



Berzelius', Rose's and Marignac's analyses of the double 

 fluoride of tantalium and potassium show that the fluorine 

 is combined with Ta and potassium in proportions of two 

 to Ave. The salt has also exactly the crystal form of the 

 niobium salt. Hence the acid is a ditantalic pentoxide. 

 Four experiments were made on this salt by drying at 

 100°, moistening with sulphuric acid and heating grad- 

 ually till the excess of acid was driven off". The potassic 

 sulphate was leached out, evaporated, melted and weighed, 

 and the tantalic acid heated to redness and weighed. The 

 mean potassic sulphate contents was found to be 44.29 per 

 cent; extreme difterence, 0.15. The mean amount of tan- 

 talic acid obtained was 56.59; extreme difference, 0.25. If 

 K = 39, these data give Ta =: 182.3. Four analyses were 

 also made of the ammonium salt. This contained traces 

 of potassium which were determined and allowed for in 

 each case. The mean amount of tantalic acid obtained was 

 65.25 per cent; extreme difference, 0.34. This gives Ta = 

 182, the number which Marignac adopts. The salts were 

 obtained by dissolving tantalic acid, which had not been 

 heated to redness, in fluohydric acid, adding potassic or 

 ammonic hydrate and purifying by recrystallization. These 

 salts are much less soluble than the corresponding niobium 

 and titanium salts. {Liebicfs Ann., S. 4-, 1866, 234.) 



TELLURIUM. 



Regnault and Kopp have each determined the specific 

 heat of tellurium and found it in accord with an atomic 

 weight of about 128. [Gmelin- Kraut, I. c.) 



