130 H. D. Newton — Volumetric Estimation of Titanium. 



Art. XYII. — A Metliod for the Volumetric Estimation of 

 Titanium / by H. D. Newton. 



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



About forty years ago, F. Pisani* stated that titanic acid 

 could be estimated by reduction with zinc in hydrochloric acid 

 solution, the action being hastened by gentle heat, and, after 

 the reduction was complete, pouring off the undissolved zinc, 

 washing and titrating with potassium permanganate. Pisani, 

 while stating that the above procedure gave excellent results, 

 gave no test analyses. Marignacf applied Pisani's method, 

 shortly after its publication, to the estimation of titanic acid in 

 the presence of niobic acid. Marignac's procedure differed 

 slightly, however, from Pisani's, in that the titanic acid was 

 reduced out of contact with the air, by means of a long bar of 

 zinc extending well up into the neck of the flask, the zinc 

 being removed after the reduction was completed and the solu- 

 tion titrated directly in the flask. The test analyses given are 

 good, though the results are low, especially when large quanti- 

 ties of titanic acid are used. 



Somewhat later, Wells and Mitchell:}; modified Pisani's 

 method, as improved by Marignac, by using sulphuric acid 

 solutions and protecting the solution from oxidation during 

 cooling and titration by means of a stream of carbon dioxide. 

 The experimental results are still below the theory, the greater 

 portion of the error being attributed by the authors to the 

 oxidizing action of the air, which gained access to the liquid 

 in spite of the precautions taken. 



The work to be described is a result of an attempt to elimi- 

 nate the oxidizing action of the air by reducing and cooling 

 under an atmosphere of hydrogen, and converting the equiv- 

 alent of titanium sesquioxide to ferrous sulphate by intro- 

 ducing an excess of ferric salt. A cold solution of a ferrous 

 salt, as is well known, is very slowly acted upon by atmospheric 

 oxygen. § 



The reaction between the salts of titanium and iron takes 

 place according to the following equation : 



_ Ti 2 (S0 4 ) 3 + Fe 2 (S0 4 ) 3 = 2Ti(S0 4 ) 2 + 2FeS0 4 



For this work, the titanium solutions were made by treating 

 recrystallized potassium titanofluoride with concentrated sul- 

 phuric acid, evaporating the mixture to the fuming point of 

 the acid, and diluting to a known volume. The resulting solu- 

 tions were standardized by the basic acetate method, || slightly 

 modified in the present case, owing to the absence of any iron 

 in the solutions used. 



*Compt. Rend, lix, 298. \ Zeitsehr. Anal. Chem., vii, 112. 



% Jour. A. C. S. xvii, 878. § Peters & Moody, this Journal, xii, 367. 



I Gooch, Amer. Chem. Jour., vii, 283. 



