Professor Berzelius on Thorina, 93 



then, with sulphuric acid, a determined weight of the sulpho-* 

 salt, thrown down by boiling, and afterwards evaporated over a 

 lamp till fumes ceased to be given off. In the greater number 

 of experiments, fumes ceased to be given off at a point which 

 denoted an increase of one half in the quantity of acid contained 

 by the salt ; but this quantity was by no means precise : some- 

 times a little more was obtained, sometimes less ; but, in the 

 last case, a portion of the salt did not immediately dissolve in 

 water. In every case, I found an anhydrous salt formed by the 

 presence of more sulphuric acid. 



To get out of this labyrinth, I prepared and analyzed a por- 

 tion of anhydrous chloride of thorium. This analysis gave for 

 the atomic weight of thorina, .838. I regard this number, 

 however, as less worthy of credit than the formerly obtained 

 mean, since in this case the earth was coloured by some foreign 

 substance, probably iron. 



If we take the mean of the results obtained from the sulpho- 



salts, as nearest the true atomic weight, then thorina in 100 



parts will consist of 



Thorium 88.16i,^^ 

 Oxygen 11.84/'"" 



And the hydrate of thorina will consist of 



Thorina 88.25 1,^^ 

 Water 11.75j'"" 



The symbol for an atom of thorium =744.9 may be Th, for 

 thorina Th, and for its hydrate Th H. 



Thorina is distinguished generally from the other earths by 

 its forming with sulphuric acid a compound which, by boil- 

 ing, lets fall a while salt, dissolving again, though slowly, on be- 

 coming cold. In applying this test, however, it must be re- 

 marked that this precipitation is prevented by the presence of 

 those bases with which thorina forms double salts, from which 

 by boiling no appreciable quantity falls. 



From alumina and glucina it is distinguished by its being 

 insoluble in caustic potash, by which these earths are taken up. 



From ytfria, by its forming with sulphate of potash a 

 double salt insoluble in a saturated solution of sulphate of 

 potash, by which means it may sometimes be separated quan^ 

 titively from yttria. 



From zirconiaj by these two circumstances, that zirconia pre- 

 cipitated hot by sulphate of potash becomes afterwards, in a 



