Professor Berzelius on Thorina, , 81 



crystallized, although, from its being so easily soluble, with 

 great difficulty. 



Bromide of thorium is prepared by dissolving hydrate of 

 thorina in hydro-bromic acid. The solution, which contained 

 an excess of acid, was left to spontaneous evaporation; a 

 tenacious, gummy-like mass, was formed, which, on driving off 

 the excess of acid, became of a deep orange-colour — a hue which 

 was not changed by several days' direct exposure to the solar 

 rays, at a temperature of +30® (Celsius = 86° Fahrenheit*.) 



When a little bromide of potassium is added, a double salt 

 is formed, and the bromine speedily evaporates. 



Fluoride of thorium is insoluble in water, and in hydro- 

 fluoric acid. It is obtained by dissolving the hydrate in fluoric 

 acid. When the supernatant excess of acid is evaporated, 

 there remains almost no residue. The fluoride of thorium is 

 a heavy, enamel-white powder, which is not decomposed by a 

 red heat, and very imperfectly by potassium. 



The fluoride of thorium and potassium is a salt, insoluble 

 in water, which falls when a salt of thorina is mixed with 

 fluoride of potassium. It is not decomposed by heat; but 

 potassium reduces the thorium, though always silently. 



Cyanide of iron and thorium is obtained when a salt of 

 thorina, containing no excess of acid, is mixed with a solution 

 of cyanide of iron and potassium. The slightest trace of tho- 

 rina is discovered by this means. The precipitate is heavy and 

 enamel-white. Acids dissolve it, and alkalies decompose it, 

 separating hydrate of thorina. By the red cyanide of iron and 

 potassium the salts of thorina are not troubled. 



* I have endeavoured to find out the cause of this colouring, and found it to be 

 derived from a property which iodine has in a high degree, bromine in a less, 

 and which chlorine altogether wants, namely, that they give higher degrees of 

 combination than correspond witli those of oxidation (iln som svara emot oxiderna). 

 Iodine has this proj^erty, even with the strongest bases, potassiinn and sodium, 

 and gives very soluble crystalline high degrees of iodic combination, with calcium, 

 magnesium, &c., which, with the earthy hydrates, form insoluble subsalts. Di- 

 gestion, with much water, decomposes these, and separates the earth. Bromine 

 exhibits these high degrees of combination, which are decompose*! by water, with 

 the weaker metallic bases only, of which we have an example in the bromide of 

 calcium. Hydrate of lime, treated with bromine in excess, and afterwards eva- 

 porated in the vacuum of an air-pump, over dry caustic potash, gives a solid, cinna- 

 barred mass, which i^ decomposed by water in such a way, that a yellow powder is 

 separated, and a bleaching liquor formed ; but all colour is speedily lost, and 

 with it the bleaching property. Tlie liquid then contains bromide of calcium and 

 bromate of lime. In an analogous way, the orange bromide of thorium contains 

 a chemical combination of bromine, witn neutral bromide of thorium. 



JAN.— -MARCH, 1830. H 



