174 



_ It seemed, therefore, of interest to investigate the sublect. and espe- 

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

 sults might throw .ome light on the action between it and the chlorate 



The substances chosen for the preliminary work were potassium ni- 

 trate and potassium bichromate. AMu-u potassium nitrate is heated to 

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

 It molecular proportions of the nitrate and manganese dioxide are mixed 

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

 2So C. Between that temperature and .350° C. there is a constant, though 

 not rapid, evolution of a gas which give-s the usual test for oxvgen The 

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

 brown oxides of nitrogen. In the same bath was a tube containing the 

 same weight ..f pure dric.l potassium nitrate bur there was no evidence of 

 <iuy decomposition. Dnring the heating some moisture collected in the 

 <^older part of the tube, but whether this had any effect in causing the 

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

 has not yet been determined. 



When potassium bichromate is heated alone in a fn'o bunsen tiame 

 little or no oxygen is evohed even at the highest temperature obtainable. 

 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 i;,pi,nty up to 850°. The tempera- 

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

 the same that a similarity of action is suggested. A^'hether the oxyo-en 

 comes from the oxide, the other substaiH-e .)r from I,oth has not vet been 

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

 of oxygen is certain. The investigation will be continued along this and 

 related lines and the nature of the acti..ns will be thoroughlv 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. 8uch a sub- 

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

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



