170 



Investioation ()F Till-; AriroN I^KTWEEN' Man(;anese Dioxide and 



I'OTASSrU.M CilEORATE I.V THE 1*R0DUCTI0N OF OxY(;E.V. 

 Edwakd G. Mahin. 



The method for preparing oxygen by heating mixtures of potassium 

 chlorate and manganese dioxide lias lieen used ))y ch.'mists for some time. 

 Since, howevci'. the manganese dioxide comes out uncliaiig<'d at the end 

 of the process, yet consideralily lowers the tem])erature necessary for de- 

 composition of potassium chlorate, its exact function has been and is yet 

 imperfectly understood. 



There is not inly a practical, bul also a vci'v interesting theoretical 

 (pU'stion inyolve<l in tlic cxplaiialion of tlic i-eaclion taking place in this 

 jirocess. and it was tlie desire for obtaining fintlier liglit on certain 

 points that led I'rofesscu' Kansom and the writer, at the suggestion 

 of the fornuM-. to jointly undei-taice a study of the facts. Some questions, 

 the settienient of wliicli was to 1ie attempted, \\-ere: 1. Doi's variation in 

 proportion of potassium chlorate and manganese dioxide affect the tem- 

 l>eratui'e at which oxygen is evolved, and. if so. what ndxture yields it at 

 the lowest temjierature? 2. Is tlie action continuous wlien the mixture 

 is heated for a long period at or .just above tlie decomposition tempera- 

 ture, and what are the products? '.\. Heating foi' .i period just below this 

 temperature, are any intermediate products foi'iued and what are they? 

 4. To notiic any new facts Iircnight out by tlie experimental work. 



Search of tlie literature sliows that tlu' men who have performed the 

 most imjiortaiit work uixui this part iculai' phase of the subject are INIc- 

 I-eod. P.runck and Sodeau. .Mcl.eod li.nj noticed the well-known fact that 

 a gas resembling chlorine was evolved with oxygen, and in 1S80, pub- 

 lished a statement of experim.Mital work, deducing the following reactions: 



2 Mn O2 + 2 K CI Or, = K2 Mn2 Os + CI2 -|- ()2. 

 K2 Mn2 Ok = K2 Mn O4 -f Mn O2 + O2. 

 K2 Mu O4 + Cl2 = 2 KCl I Mn O2 f O2. 



T'pon this basis he explained the sujiposed fact that free chlorine is 

 evolved only at the beginning of the process, since chlorine is liberated by 

 the first reaction and at the lowest temperature, and that corresponding to 

 this free chlorine, there was a certain amount of undecomposed potassium 

 mansanate at the end. In IS!).". Brunck argued that if these reactions 



