302 Gooch and Danner — Points in the Interaction of 



oxalic acid and the permanganate in whatever way the condi- 

 tions were varied — whether there was excess of oxalic acid or 

 of permanganate, whether the solutions were strong or dilute, 

 whether acid was present or not — in every case oxygen was 

 obtained as a product of the reaction. The action between 

 the permanganate and ferrous salts, in presence or absence of 

 acids, in dilute or strong solutions, was said to yield oxygen 

 similarly. In the discussion which followed the reading of 

 this paper before the Chemical Society (London) some adverse 

 comment seems to have been developed.* 



More recently,t in developing his excellent volumetric 

 methods for the estimation of tellurium, Professor B. Brauner 

 has noticed a similar effect in the action of potassium per- 

 manganate upon tellurous oxide dissolved in sulphuric acid, 

 and has shown, further, that in this particular case the evolu- 

 tion of oxygen is proportional to the amount of sulphuric 

 acid employed, and that in working with alkaline solutions 

 little evidence of such action appears. 



The production of permanganic acid, and secondarily of 

 free oxygen and ozone, by the action of strong sulphuric acid 

 upon a permanganate is one of the commonest of phenomena, 

 and the formation of a precipitate consisting largely of 

 hydrated manganese dioxide by the action of hot dilute sul- 

 phuric acid upon the permanganate in aqueous solution is 

 likewise well-known. It seemed desirable to us, therefore, to 

 study further the action of sulphuric acid of different strengths 

 upon the permanganate in solution, with a view to determin- 

 ing how far such action may be responsible directly or indi- 

 rectly for the liberation of free oxygen in oxidations brought 

 about in the presence of the acid. In the first set of experi- 

 ments directed to this end we determined the amount of potas- 

 sium permanganate remaining after exposure to the action of 

 sulphuric acid during different intervals of time and under 

 varying conditions of strength and temperature. The per- 

 manganate was used in approximately decinormal solutions 

 (3 - 16 grms. to the liter) the exact strength of which was 

 determined relatively to an approximately decinormal solution 

 of oxalic acid. In fixing the standard small portions (usually 

 10 cm 3 ) of the oxalic acid were diluted to a volume of 100 cm 3 

 by means of sulphuric acid of two per cent strength by vol- 

 ume, the solution was heated to 70° C. or 80° C., and the 

 permanganate was added as usual until the first permanent 

 blush of color appeared. 



The general mode of proceeding in the test experiments 

 was, in brief, to mix the solution of permanganate with the sul- 



*Ber. d. d. Chem. GeselL, 1878, p. 257. 

 f Jour. Chem. Soc, 1891, p. 238. 



