OP ARTS AND SCIENCES. 445 



first, — and appears in the description to be long and tedious, may in 

 reality be carried out with ease and rapidity, the operations being 

 generally short and not of a difficult nature. 



In most cases in which titanium is to be separated from aluminum, 

 it is necessary to effect the removal of iron as well. Some experi- 

 ments looking to the separation of titanium and iron, by boiling the 

 acetates in presence of a large excess of acetic acid, were unsuccessful ; 

 for, though an excess of acetic acid amounting to eleven per cent of 

 absolute acid in the solution is enough to prevent the deposition of a 

 basic ferric acetate, it appears, unexpectedly, that in presence of ferric 

 acetate in solution the titanium shows a very marked tendency to 

 remain dissolved. Thus, an amount of iron alum the equivalent of 

 0.2 grra. of ferric oxide, together with 10 grm. of sodic acetate and 

 seventeen per cent of absolute acetic acid, in a total volume of 400 cm.^, 

 held 0.06 grm. of titanic oxide coH)pletely in solution during 

 boiling prolonged a quarter of an hour. In an experiment the coun- 

 terpart of this, excepting only the addition of sodic acetate, the 

 titanium began to deposit at once on boiling ; and Streit and Franz,* 

 in proposing the ebullition of the sulphates in presence of a large ex- 

 cess of acetic acid as a means of procuring titanic oxide free from iron, 

 claim a complete precipitation under these conditions. The behavior 

 of the suljihates of titanium and zirconium when in solution together 

 appears to be analogous to this action of the acetates of iron and 

 titanium, and iron in the ferric condition is generally supposed to 

 influence somewhat the precipitation of titanium from the solution of 

 the sulphates. 



When iron and titanium appear together in solution, and are to be 

 separated, the choice lies between Stromeyer's application of Chancel's 

 hyposulphite method,! which yields milky filtrates, — always undesira- 

 ble, — and that process which involves the precipitation of iron by 

 amnionic sulphide in presence of ammonic tartrate to hold up the 

 hydrates which would be precipitated in its absence. This latter 

 method has been regarded as an undesirable one chiefly on account ot 

 the inconvenience involved in the evaporation of the filtrate from the 

 ferrous sulphide and the ignition of the residue to remove the tartaric 

 acid, and so to permit the recovery of bases. The difficulty in question 

 may be obviated, however, by destroying the tartaric acid by potassic 

 permanganate added gradually to the hot solution containing enough 

 free sulphuric acid to leave some excess after the conversion of all the 



* Jour, prakt. Chem., cviii. G5. t Ann. Ch. Pharm., cxiii. 127. 



