9d Professor Berzelius on Thorina, 



2. Thorina^ which is formed by the union of the metal with 

 oxygen, and seems to be its only state of oxidation, has the 

 following properties : — It is colourless ; heavy ; soluble only in 

 concentrated sulphuric acid, aided by a high temperature. 



Preparation of thorina from thorite. — The mineral is dis- 

 solved in sulphuric acid, in the way stated above in the analysis. 

 The solution is treated with sulphuretted hydrogen, and the 

 earth precipitated by ammonia. The precipitate, collected on 

 the filter and well washed, is dissolved in dilute sulphuric acid^ 

 and the solution evaporated by heat. By this means, there is 

 formed a bulky sulphate, which is separated before the liquid 

 is completely evaporated, washed with boiling water, pressed 

 between folds of paper, dried, and heated to redness : what 

 remains is pure thorina. 



The mother liquor and the washing still contain thorina ; the 

 excess of acid is saturated, as nearly as possible, with caustic 

 ammonia: oxalic acid is then added, so long as any precipitate 

 falls ; and the precipitate, washed with water, slightly acidulated 

 with oxalic acid. By this process, the manganese, iron and 

 uranium remain in solution, and the oxalate of thorina is ob- 

 tained on the filter. This gives, after burning, an earth tinged 

 with yellow, arising from a small taint of peroxide of manganese, 

 which attaches itself more strongly than other substances to 

 this earth. 



Thorina may also be precipitated from this solution by adding 

 dry crystallized sulphate of potash, as long as any is dissolved* 

 The thorina falls in the form of a double salt ; and by this 

 process it is more completely thrown down than by oxalic acid. 



To obtain the hydrate of thorina, the sulphate of thorina, 

 after washing with boiling, is dissolved in cold water. This 

 salt dissolves very slowly, but at length completely: the solu- 

 tion is precipitated by caustic potash, and washed upon the 

 filter ; the precipitate is gelatinous, like the hydrate of alumina, 

 but falls easily ; during washing and drying it absorbs carbonic 

 acid from the air ; dried in the open air, it forms itself into 

 glassy lumps ; in a vacuum over sulphuric acid it is obtained 

 in the form of a white powder ; it loses its water by a low red- 

 heat. The moist hydrate dissolves easily in acids ; when dry, 

 it dissolves with great difficulty and after long digestion ; but, 

 after heating to redness, it becomes altogether insoluble in 

 nitric and muriatic acide, ' 



