173 



The tubes were kept at loo'-JJU^ for four and a bait' lioiirs: no gas was 

 over beyond that due to simple expansion, and not the sliglitest trace of 

 either chlorine or ozone was found in any generator tube. No oxygen 

 could be discovered. The mixtures upon testing were found to contain a 

 considerable amount of clilorides. The temperature was raised to and 

 kept at 150° for tiiree hours and no chlorine or oxygen was produced. 

 The quantity of chlorides seemed to be increased. At 17o° all of the tubes 

 began to evolve oxygen and so long as this temperature was maintained 

 a steady but slow stream of oxygen was produced. No trace of chlorine, 

 chlorine oxide or ozone was produced as high as 180°. 



At this point the work was stopped for lack of time. Thus far a few 

 conclusions may be provisiouallj- advanced: 



The conditions under which oxygen is ordinarily produced are not 

 ideal, and the moisture always present materially intinences the reactions. 

 This moisture makes possible the production of oxygen at a lower tempera- 

 ture than in the case of dry materials, also the formation of chlorine or 

 chlorine oxide, or both, as low as 125° and lief ore oxygen is evolved. This 

 may be due to hydrolysis of the potassium chlorate or chloride, thus allow- 

 ing oxidation by the manganese dioxide. It is possible and even probable 

 that no chlorine would be evolved at any temperature within the ordinary 

 range of heating, if the materials were entirely free from moisture. In 

 such a case, McLeod's explanation must fail, since if it be true, the forma- 

 tion of free chlorine is a necessary step in the evolution of oxygen. 



This point, witii others mentioned, will be more fully investigated by 

 future Avork. and it is hoped that some facts of interest may be brought 

 out during the investigation. 



AcTiox OF Heat i»x Mixtcres of Manganese Dioxide With 

 Potassium Nitrate and With Potassium Ukiiromate. 



J. H. Kaxsom. 



The fact that different metallic oxides mixed with potassium chlorate 

 cause the latter to evolve oxygen at considerably lower temperatures than 

 when heated alone has long been known, though the natttre of the chemi- 

 cal action involved is not with certainty established. No work has been 

 done, so far as I am aware, to see what the effect of these oxides might 

 be on other sulistances decomposable )jy heat. 



