OF ABTS AMD SCIENCES. 435 



XX. 



ON THE SEPARATION OF TITANIUM AND ALUMINUM, 

 WITH A NOTE ON THE SEPARATION OF TITANIUM 

 AND IRON. 



By F. A. GoocH. 



Communicated May 13, 1885. 



In attempting to separate titanium and aluminum it is usual to resort 

 to that method which depends upon the action of the slightly acid 

 solution of the sulphates when submitted to prolonged boiling. The 

 faultiness of this method, however, becomes apparent when solutions 

 of aluminum and titanium are compared as to behavior under the 

 conditions. To secure the complete precipitation of titanium the 

 excess of sul{)huric acid must be kept small, while to prevent the 

 deposition of alumina the acid must be more than enough to dissolve 

 the same amount freshly precipitated as hydrate, in the cold. Thus, 

 upon boiling solutions containing the equivalent of 0.06 grm. of 

 titanic oxide, 2.5 grm. of free sulphuric acid, beside alkaline sul- 

 phates, in 800 cm.^ of water, it was found that at the end of an 

 hour 0.003 grm. of titanic oxide in one case, and 0.006 grm. in 

 another experiment, had escaped precipitation ; but that, when the 

 solution of titanium had first been precipitated by ammonia and then 

 made just acid by sulphuric acid, every trace of dissolved titanium 

 was tlirown out on boiling. The experiment, on the other hand, 

 of boiling a gram of alum — roughly speaking 0.1 grm. of alumina 

 — in 800 cm.** of water shows almost immediately the deposition 

 of some alumina, and the same thing happens when the alumina 

 is first precipitated by ammonia and then dissolved by just enough 

 sul[)huric acid to effect the solution. The difficulty of so adjusting 

 the acidity of the solution that no alumina shall be deposited and 

 no titanium held up, is obvious. Test paper is of no aid in the 

 case, since the reaction of alum itself and aluminic sulphate is 

 acid. Under the circumstances it is hardly surprising that Knop* 

 should revert from the troublesome, and only under remote con- 



* Jahrb. f. Slin. 187G, p. 750; Zeit. f. Kryst. u. Min., i. 58. 



