46 Brown — Work on the Interaction of Hydrochloric Acid. 



Here it is shown, as with ferric chloride in the previous 

 paper, that the chlorine held in solution is responsible for the 

 low indications of the amount of permanganate apparently- 

 reduced during digestion when no means are used to remove 

 this chlorine. With cadmium chloride and chlor-auric acid the 

 same amount of permanganate is here shown to be reduced as 

 when the permanganate is digested with hydrochloric acid 

 alone, and it is further seen that the maximum eifect is accom- 

 plished by thirty minutes heating. In all experiments in 

 which chlor-platinic acid was used the oxides of manganese, 

 noticeable in those experiments in which ferric, cadmic, and 

 chromic chlorides were used, were entirely reduced, and the 

 liquid at the close of the digestion was perfectly clear, showing 

 only the color due to the chlor-platinic acid ; when the chlorine 

 is removed in these experiments the permanganate required to 

 bring about final coloration is substantially equal to the oxalic 

 acid added, the slight excess over this value being due probably 

 to difficulty of distinguishing the end color. In the last two 

 experiments the values are a little below that corresponding to 

 the oxalic acid ; this may be due to a slight residue of man- 

 ganese oxides which appeared not to be entirely reduced at the 

 end of the half hour's digestion. This point, however, has not 

 been sufficiently investigated to be definitely decided. With 

 chromic chloride we find a variety of phenomena. In all ex- 

 periments shown in Tables I and II the permanganate is 

 entirely reduced and the chromic chloride is partially oxidized, 

 leaving at the end of the digestion a clear liquid greenish- 

 yellow in color. When the oxalic acid is added the chromic 

 acid is reduced totally or in part, tending to restore the origi- 

 nal green color to the solution, but the chromic chloride does 

 not seem to be oxidized to any noticeable extent on running in 

 permanganate to color, the end reaction showing a green liquid 

 colored faintly by the permanganate. In an experiment show- 

 ing such a variety of reactions, most of which are indefinite, 

 concordance of results is not to be expected even when the 

 chlorine is removed, and the experiments of Tables I and II, 

 in which chromic chloride were used, show wide variation. 



Wagner* has noted the separation of hydrated oxides of 

 manganese with all his " catalyzers " except gold and platinum. 

 The exception holds for platinum but not for gold, in my ex- 

 perience, as with the latter the same residual oxides of man- 

 ganese are noticeable as with ferric and cadmic chlorides. 

 With chromic chloride I found no residual oxides, as already 

 stated, Wagner's statement to the contrary notwithstanding. 



It will be seen by a comparison of the results of Table I of 

 this paper with those of Table I of the previous paper, that 

 although in both tables the " KMn0 4 apparently reduced dur- 

 ing digestion " is greater in the presence of the metallic chlor- 



* Loc. cit., page 87. 



