Existence of Titanic Acid in Hessian Crucibles, 115 



6. The alumina was next obtained by boiling the alkaline 

 solution with an excess of muriate of ammonia for some time: 

 the resulting gelatinous precipitate was washed, ignited, and 

 weighed. 



7. The liquor (3.) from which the titanic acid, alumina, and 

 peroxide of iron were separated, contained traces of magnesia 

 and manganese. 



The results obtained by examining several specimens, dif- 

 fered very considerably, as may be seen by comparing together 

 the following results of four analyses : 



Silicic acid 



Titanic acid 



Alumina 



Ptroxide of iron 



^^agnesia 



Oxide of raansanese 



Loss 



In a very few specimens we have found the titanic acid to 

 be present in very minute quantities, and in one or two only 

 we could not succeed in detecting any. It is a very difficult 

 matter to free the titanic acid from the peroxide of iron, the 

 last traces of which adhere exceedingly obstinately to the acid; 

 the process recommended by Berzelius, viz. adding tartaric 

 acid to the acid solution of the mixed oxides and the subse- 

 quent precipitation of the iron by hydrosulphuret of ammonia, 

 by no means succeeding perfectly. The use of oxalic acid for 

 the purpose of precipitating the titanium and leaving the iron 

 in solution is not more efficient, as the precipitate is found to 

 be contaminated with a considerable quantity of peroxide of 

 iron. The following is the process we prefer for the purpose 

 of obtaining the titanium, free from iron. Ignite a mixture 

 of carbonate of potass and powdered Hessian crucibles; 

 digest the mass thus obtained in warm water for some 

 time: this aqueous solution yields a very slight grass-green 

 tinge with hydrosulphuret of ammonia. Dissolve the portion 

 insoluble in water in hydrochloric acid, with the assistance 

 of a gende heat ; dilute and filter the acid solution and wash 

 the residue on the filter ; when the acid has almost entirely 

 passed the filter, the washings become opaline. The filtered 

 fluid is then to be nearly neutralized with ammonia, and hy- 

 drosulphuret of ammonia added: a deep green precipitate 

 falls, which is to be collected on a filter and washed with a di- 



Q2 



