142 Palmer — Potassitim Ferrioyanide in Alkaline Solution. 



ponnani>-aiiate, as, if not removed, it would form a precipitate 

 with the ferrocyanide. The removal of the vanadium was 

 effected by means of a solution of barium hydroxide, which 

 completely precipitated the vanadium as barium vanadate ; this 

 precipitate, after settling, was filtered off on an asbestos felt, 

 and the filtrate and washings were acidified with hydrochloric 

 acid and titrated with permanganate. Titration in sulphuric 

 acid solution was unsatisfactory on account of the difficulty in 

 noting the end point in the presence of the precipitate of 

 barium sulphate which was formed by the action of the sul- 

 phuric acid on the excess of the barium salt, and it has been 

 found, in connection with the previous work, that, unlike the 

 case of ferroiis salts, ferrocyanide may safely be titrated by 

 permanganate in the cold in dilute hydrochloric acid solution. 

 The results of the determinations are recorded in Table I. 







T. 



\BLE I. 









V.Os 



KaFeCoNo 



KOH 



VaOr. 







taken 



used 



used 



found 



Error 





grm. 



grm. 



grm. 



grm. 



grm. 



<1) 



0-0960 



4 



6 



0-0959 



-0-0001 



(2) 



0-0960^ 



4 



6 



0-0954 



— 0-0006 



(3) 



0-0960* 



4 



6 



00956 



— 0-0004 



(4) 



0-0960 



4 



6 



0-0962 



+ 0-0002 



(5) 



0-0960 



4 



6 



0-0956 



-0-0004 



(6.) 



0-0960 



4 



6 



0-0959 



— 0-0001 



(7) 



0-0960 



4 



6 



0-0961 



+ 0-0001 



(8) 



0-0960 



4 



6 



0-0961 



+ 0-0001 



(9) 



0-0960 



4 



6 



0-0960 



±0-0000 



(10) 



0-0960 



4 



6 



0-0961 



+ 0-0001 



Estimation of Chromium. 



As Bollenbaeh and Luchmann have recently shown,* chro- 

 mium may be quantitatively oxidized from the condition of 

 Cr^Oj to the condition of CrOg by potassium ferricyanide in 

 alkaline solution, and a measure of the oxidation obtained by 

 titrating with permanganate the ferrocyanide formed. 



According to their method an excess of at least 4 to 6 times 

 the theoretical amount of potassium ferricyanide and 40 to 50 

 cubic centimeters of a 2-normal solution of sodinm hydroxide 

 were added to the solution containing the chromium to insure 

 complete oxidation of the chromium. The oxidized chromium 

 was i-emoved by precipitation as barium chromate by means 

 of barium hydroxide solution, and filtration. The filtrate was 

 then acidified with hydrochloric acid and titrated with perman- 

 ganate according to BoUenbach's modification of De Haen's 

 method,! designed to overcome the difficulty involved in 



* Zeitschr. fiir anorg. Chem., Ix, 446. 

 f Zeitschr. fiir anal. Chem., xlvii, 687. 



