Gooch and Newton — Method for the Estimation of Iron. 365 



Art. XXXV. — A Method for the Estimation of Iron in 

 presence of Titanium,' by F. A. Gooch and H. D. 

 Newton. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — clvi.] 



Fob analytical purposes, a ferric salt in solution is most easily 

 and conveniently reduced to the ferrous condition by the action 

 of zinc ; and where many determinations of iron are to be 

 made, the use of the well known reductor, first proposed by 

 Jones* and described in simple form by Blair,f yields accurate 

 results very rapidly. The use of zinc, whether in the flask or 

 in the reductor, has, however, been precluded when the ferric 

 salt is accompanied by titanic acid, for this substance is reduced 

 with the iron and subsequently oxidized by the permanganate 

 in the titration process. When, therefore, titanium is present 

 with the iron, it has been customary to have recourse to other 

 methods of reduction. In this event, either hydrogen sulphide 

 or sulphur dioxide is substituted for the zinc to bring about 

 the reduction of the ferric salt, while titanic acid is not reduced 

 by these reagents ; but the removal of the excess of hydrogen 

 sulphide or of sulphur dioxide from solution without oxidation 

 of the ferrous salt is not an easy or rapid process. 



The present investigation was undertaken for the purpose 

 of adapting the ordinary convenient process of reducing the 

 ferric salt by zinc to the estimation of iron in presence of tita- 

 nium. It is obvious that to solve this problem it is only neces- 

 sary to find and employ some reagent which shall be neutral 

 toward the ferrous salt but capable of reoxidizing the titanium 

 compounds formed by the reducing action of the zinc and with- 

 out action on the permanganate. Compounds of silver, copper, 

 or bismuth oxidize very easily the reduced titanium salt ; but 

 the use of a compound of silver is precluded by the fact that it 

 oxidizes also the ferrous salt to some extent as well as the tita- 

 nium salt. Cupric salts and pure bismuth oxide prove, how T - 

 ever, to be without action upon the ferrous salt. 



For the work to be described, ferric oxide was prepared 

 from pure ferrous oxalate and converted to ferric sulphate, and 

 a solution of this salt was made up of convenient strength and 

 standardized by reducing the iron with zinc in a small flask, 

 as recommended by Blair,;}: and titrating with potassium per- 

 manganate. Titanium sulphate was prepared in solution by 

 digesting pure titanic acid in concentrated sulphuric acid and 

 diluting the filtered solution to known volume. 



* The Chemical Analysis of Iron, Blair, 2d edition, p. 203. 



flbid., 6th edition, p. 94. 



% The Chemical Analysis of Iron, Blair, 6th ed., p. 225. 



