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



In preliminary experiments it was found that the violet color 

 of the solution containing the titanium compound produced by 

 the action of zinc upon the titanium sulphate was discharged 

 by adding a little cupric sulphate to the solution and heating, 

 and, after filtering, a drop of potassium permanganate gave its 

 characteristic rose tint to the solution. It was found also that 

 when cupric oxide was added to a similarly reduced solution of 

 the titanium salt the characteristic color vanished on shaking the 

 solution. The following table contains the results obtained in 

 titrating with potassium permanganate the ferrous salt left 

 after reducing by zinc in small flasks carefully measured 

 amounts of ferric sulphate and titanium sulphate, treating the 

 mixture thus obtained with cupric sulphate or with cupric 

 oxide, and filtering off the reduced copper and cuprous salt. 







Table I. 





Fe 2 3 

 taken 

 grm. 



Ti0 2 

 taken 

 grm. 



Fe 2 3 



found 

 grm. 



Error 



0-1375 

 0-1375 

 0-1375 



o-i 

 o-i 

 o-i 



0-1378 

 01374 

 0-1377 



+ 0-0003 



—o-oooi 



+ 0-0002 



0-1375 

 0-1375 

 0-1375 



o-i 

 o-i 



•0-2 



0-1378 

 0-1378 

 0-1382 



+ 0-0003 

 -J 0-0003 

 + 0-0007 



Treated 

 with CuS0 4 



Treated 

 with CuO 



So it appears that either cupric sulphate or cupric oxide may 

 be used to reoxidize the salt of titanium reduced by zinc, with- 

 out affecting appreciably the ferrous salt in solution. 



Similar experiments in which bismuth oxide was substi- 

 tuted for the copper oxide are recorded in Table II. To 

 the measured amount of ferric sulphate and titanium sul- 

 phate contained in a small flask, provided as usual with the 

 funnel valve, zinc was added and the reduction effected in the 

 ordinary manner. The titanium salt appears to act catalyti- 

 cally in this process, so that reduction goes on more easily and 

 with less expenditure of zinc than in the similar reduction of 

 the ferric salt taken by itself. After the zinc had disappeared, 

 the solution, of characteristic violet color, was cooled in the 

 flask, treated with a little bismuth oxide, gently shaken, 

 filtered from the excess of bismuth oxide and the precipitated 

 bismuth into about a liter of cold water, and titrated with stand- 

 ard potassium permanganate. 



In Table III are given the results obtained when reduction 

 was effected by passing the ferric sulphate solution through a 

 column of amalgamated zinc, 20-30 mesh, used in the simple 



