36 Brown — Hydrochloric Acid and Potassium 



Here again ma} T be noted the concordance of results when the 

 chlorine is all removed before the addition of oxalic acid, as 

 well as the fact that under these conditions substantially the 

 same amount of permanganate is required to bring about the 

 end reaction, whether ferric chloride is present or not ; and 

 that consequently as much permanganate is reduced during the 

 digestion in the latter case as in the former. Also by a com- 

 parison of experiments YIII-X and XVIII-XX, in which a 

 slight trace of chlorine remained, with experiments I-YI and 

 Xl-XYI, in which the chlorine was entirely removed, we 

 again see the oxidizing effect of the residual chlorine on the 

 oxalic acid ; for even in the former sets of experiments, in which 

 the digestion was carried on only fifteen or thirty minutes, the 

 permanganate color had entirely disappeared at the end of the 

 digestion. The variations in the amount of permanganate 

 apparently reduced during the digestion in the experiments 

 recorded in Table I are, therefore, doubtless due to the interfer- 

 ing action of the residual chlorine held in solution. The 

 " KMn0 4 apparently reduced during digestion " in the experi- 

 ments of Table II, and in those of Table III in which the 

 chlorine was entirely removed during the digestion, represents 

 the amounts of permanganate entirely reduced to manganous 

 chloride, while the differences between these amounts and the 

 '• KMn0 4 before digestion" represent the residual oxides of 

 manganese. Similar differences in the experiments of Table I, 

 and in those of Table III in which the chlorine was only par- 

 tially removed, represent the residual oxides of manganese 

 and the chlorine retained in solution. 



The amount of chlorine held in solution when no means are 

 employed to remove it, depends largely on the form and size 

 of the flask used to contain the solutions during digestion, 

 also on the dimensions of the return-condenser, and will vary 

 according to the greater or less amount of shaking to which 

 the flask is subjected during the entire course of the experi- 

 ment. It is, therefore, evident that Wagner's experiments are 

 in no way indicative of the relative amounts of potassium per- 

 manganate reduced in the presence or absence of ferric chloride 

 other conditions being constant, but are an indication simply of 

 the greater or less retention of chlorine in solution in the form 

 of apparatus used by him ; for it has been shown that in all 

 experiments conducted within the limits proposed by Wagner 

 the permanganate is entirely destroyed and that any variations 

 in the amount of permanganate apparently destroyed during 

 digestion disappear when the chlorine is entirely removed from 

 the sphere of action. The possibility of any interfering action 

 of ferric chloride in titrations of oxalic acid by potassium per- 

 manganate is excluded by the results of the experiments of 



