Brown — Work on the Interaction of Hydrochloric Acid. 41 



Art. III. — Further Work on the Interaction of Hydrochloric 

 Acid and Potassium Permanganate in the Presence of 

 Various Inorganic Salts ; by James Brown. 



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



In a previous paper* I have shown that the effect attributed 

 by "Wagnerf to the catalytic action of ferric chloride in the 

 reaction between hydrochloric acid and potassium permanga- 

 nate is in reality due to oxidation of oxalic acid, added to 

 reduce the residual oxides of manganese, by the chlorine 

 formed during the reaction. Wagner's results of a similar 

 nature with the chlorides of chromium, cadmium, gold, and 

 platinum, from which he argues that these salts also act cataly- 

 tieally in the reaction under consideration, have recently been 

 investigated, and it has been found that with the chlorides of 

 gold and cadmium the assumed catalytic effect is due entirely 

 to the chlorine retained in solution, while with the chlorides of 

 platinum and chromium the observed differences are largely 

 due to the chlorine retained in solution, but partly also to an 

 excessive reduction of the permanganate, as will be shown. 



Care was taken in this work to use pure salts, and for this 

 purpose chromic chloride, platinic chloride, and anric chloride 

 were especially prepared and purified. The chromic chloride 

 was prepared by totally reducing potassium dichromate with 

 strong hydrochloric acid, precipitating chromic hydroxide with 

 ammonium hydroxide, filtering off and washing the precipitate 

 until free from all soluble material. The chromic hydroxide 

 was then dissolved in dilute hydrochloric acid and the excess 

 of the acid removed by evaporating several times to small 

 volume, replacing the water as it evaporated. In this way a 

 solution was obtained showing slight excess of chlorine over 

 that corresponding to the chromic chloride. The platinic 

 chloride provided commercially was found to contain a con- 

 siderable quantity of ferric chloride. This was removed by 

 precipitating the platinum as the chlor-platinate with a concen- 

 trated solution of ammonium chloride and alcohol, filtering off 

 and washing with alcohol until free from all iron. The 

 ammonium chlor-platinate was then ignited to spongy platinum, 

 the latter dissolved in aqua regia, the excess of nitric acid 

 volatilized by continued heating with hydrochloric acid, and 

 the large excess of hydrochloric acid in turn removed by evap- 

 orating to small volume several times. The commercial auric 



* This Journal [41, vol. xix, 31. 



f Maassanalytische Studien, Habilitahonsschrift, Leipzig. 1898. 



