144 Palmer — Potassiuiu Ferricyanide in Alkaline Sohttion, 







Tauli 



III. 





, 





CrOs 



KoFeCoN,, 



KOH 



CrOn 







taken 



\ised 



used 



found 



Error 





grin. 



giiu. 



grm. 



grm. 



grm. 



(1) 



0-1010 



ll> 



15 



0-1016 



+ 00006 



(2) 



0-1010 



16 



15 



0-1014 



+ 0004 



(") 



0-1010 



16 



15 



0-1013 



+ 0-0003 



(-t) 



0-050,5 



10 



15 



0-1514 



+ 0-0009 



(5) 



0-0505 



16 



15 



O-OoOO . 



+ 0-0001 



Estimation of Vanadium and Chromium when present together. 



For the estimation of botli vanadinin and chromium when 

 present together, tlie foUowina; method was worked out : The 

 sohitioii contafning the vanadium and chromium, both in t,he 

 higher condition of oxidation, was divided into two portions. 

 Into one portion of the solution, made sliglitly acid with liydro- 

 chloric acid, sulphur dioxide was passed until tlie reduction of 

 the vanadium and the chromium was complete ; the solution 

 was then boiled in a current of carbon oxide until the last 

 traces of sulphur dioxide were expelled. To the cooled solu- 

 tion a sufficient excess of ])otassium ferricyanide and potassium 

 hydroxide wei-e added in solution. Bj this process the chro- 

 mium was oxidized from the condition of Cr^O, to the condition 

 of CrOg and the vanadium from the condition of Y^0^ to the 

 condition of VjO^. After allowing the solution to stand a few 

 minutes, a solution of barium hydroxide was added to complete 

 precipitation. The combined precipitates of barium chro- 

 inate and barium vanadate were filtered off on asbestos and 

 thoroughly washed ; the filtrate was made acid with dilute 

 hydrochloric acid and titrated with a known amount of per- 



manganate in excess, and the excess titrated with— potassium 

 "= ' 20^ 



ferrocyanide, according to the method given above. 



In the other portion of the solution the vanadiiim was deter- 

 mined as follows : The solution, about 100 cubic centimeters 

 in volume, was made acid with from 10 to 15 cubic centimeters 

 of glacial acetic acid, and hydrogen peroxide was added. The 

 solution was then heated to boiling and boiled for a few min- 

 utes ; by this process the perchromie acid and the pervanadic 

 acid, which were first formed in the cold, were decomposed, 

 the chromium being reduced to the condition of Cr^O^, while 

 the vanadium remained in the condition of Y.,0,,. The solution 

 was diluted somewhat, and a solution of lead acetate was added 

 to complete precipitation of the lead vanadate ; the chromium, 

 being in the condition of Cr.,03, was not precipitated. The 

 solution was stirred vigorously to coagulate the precipitate, and 



