128 Randall — Ferric Chloride in the Zinc Reductor 



Akt. YIII. — The Behavior of Ferric Chloride in- the Zinc 

 Reductor; hy D. L. Randall. 



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



The column of amalgamated zinc as applied in the earlier 

 form of the Jones reductor* or the simpler form now gener- 

 ally employed^ has proved very effective in the reduction of 

 ferric sulphate preparatory to the estimation of the ferrous 

 salt by potassium permanganate. The impression has pre- 

 vailed, however, that the salt of iron acted upon by the amal- 

 gamated zinc must be the sulphate and that chlorides and 

 nitrates must not be present even in small amounts. 



The following work was undertaken to see whether ferric 

 chloride might not be treated effectively in the reductor and 

 the reduced solution successfully titrated with standard per- 

 manganate. For this work a solution of ferric chloride was 

 made up and standardized by evaporating known amounts 

 with 10 cm3 of sulphuric acid to the fuming point of the acid, 

 passing the solution thus freed from chlorides through the 

 reductor, and titrating with standardized permanganate. In 

 general the procedure was to first run 100 cm3 of warm dilute 

 2*5. per cent sulphuric acid through the reductor, next to pass 

 in the iron solution diluted with 100 tm3 of the warm 2*5 per 

 cent acid and then to wash down with 200 cm3 of the warm 

 dilute acid followed by 100 cm3 of hot water. The receiving 

 flask of the reductor was kej>t in a vessel containing; running 

 tap water, so that the solution was cooled as fast as it was 

 reduced ; and in some of the early experiments carbon dioxide 

 was passed in at the beginning of the reduction to drive out 

 the air and at the end of the reduction before titration, a prac- 

 tice which was found to be unnecessary and so was discon- 

 tinued. In this work a column of amalgamated 20-mesh zinc 

 was used in the reductor. 



In the preliminary experiments there was some evidence in 

 the high results that chlorine was evolved, even in dilute solu- 

 tions, but this tendency was overcome by adding 1 gram of 

 manganous sulphate in solution to the receiving flask before 

 starting the reduction, according to the suggestion of Keissler^; 

 and Zimmermann§ to apply to titrations of ferrous salts by 

 permanganate in the presence of chlorides. 



Table I shows the results obtained under the varying condi- 

 tions detailed. 



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



flbid,, 4th edition, p. 94. 



\ Ann. Phys., cxviii, 41 ; cxix, 225-226. 



§Ber. Dtsch. Chem. Ges., xiv, p. 779. 



