174 



It seenu'd. tluTrforc, of intfrest to investigate the subject. ;nul espe- 

 cially the action of manganese dioxide on various substances, as the re- 

 sults might throw some light on the action l)etween it and the chlorate. 



The substances chosen for the preliminary work were potassium ni- 

 trate and potassium I)ichromate. When potassium nitrate is heated to 

 a high temperature it loses one-third its oxygen and forms the nitrite. 

 If molecular proportions of the nitrate and manganese dioxide are mixed 

 and heated in a metal bath, little if any evolution of oxygen occurs below 

 2Ho° C. Between that temperatiire and 3.50° C. there is a constant, though 

 not rapid, evolution (»f a gas which gives the usual test for oxygen. The 

 amount, however, is not large, and during the heating there are formed 

 brown oxides of nitrogen. In the .same l)ath was a tube containing the 

 same weight of pure dried i)otassium nitrate but there was no evidence of 

 any decomposition. During the heating some moisture collected in the 

 colder part of the tup)e. but whether this had any effect in causing the 

 decomposition of the mixture, as is found in the case of the chlorate, 

 lias not yet been determined. 



When potassium bichromate is heated alone in ;i free bunsen flame 

 little or no oxygen is evohed even at the highest temperature o1)tainable. 

 When mixed with manganese dioxide, however, a steady stream of gas 

 is evolved at a comparatively low temperature. The decomposition begins 

 at 285° but does not increase greatly in rapidity up to 350°. The tempera- 

 tures at which the nitrate and the bichromate decompose are so nearly 

 the same that a similarity of action is suggested. Whether the oxygen 

 comes from the oxide, the other substance or from liotli has not yet been 

 determined. That the oxide has some effect in producing the evolution 

 of oxygen is certain. The investigation will l)e continued along this and 

 related lines and the nature of the actions will be thoroughly studied as 

 soon as time permits. It will also be of interest to know whether such 

 oxides as the one used will lower the temperature at which substances 

 ordinarily decompose, but without the evolution of oxygen. Such a sub- 

 stance would be ammonium nitrate. This subject will also be inquired 

 into. In the meantime I wish to reserve this tield of investigation. 



