200 Mixta' — Formation of the Oxides of Cohalt and Nickel. 



Dulong 84-37= 



Andrews 87'20 



Favre and Silbermann j ^^."^'J 



Murignac 85-23 



f 88-16 



!>'- \v:. 



[83-22 



The mean is 85*06''. DeForcrand found for ZnO prepared at 

 125° 82-97' and for oxide made at the temperature of burning 

 zinc 84-7^ Ditte also worked with preparations of zinc oxide 

 which had been subjected to different temperatures. The 

 results of the two investigators are essentially 83-0'^ for ziije 

 oxide prepared at a low temperature. Since the combustion 

 of zinc with sodium peroxide gives only 87-0'^ it is evident that 

 the heat effect of Na^O + ZnO is very small, only i-Q large 

 calories. 



Manganese. 



7. Heat of reaction of tnanganese with sodium peroxide. — 

 Manganese for the work was prepared by the Goldschmidt 

 method. It was free from aluminum and contained a trace of 

 silicon. Three combustions of the following mixtures were 

 made: 



12 3 



Manganese 3-000 5-000 5-116 grams 



Sulphur. 1-000 1-000 0-500 " 



Sodium peroxide 17- 30- 30- " 



Result for 1 gram of manganese.. 2237"= 2043° 1985= 



The fusions were green. Number 1 gave little gas when 

 placed in water, the other two considerable gas. Tlie solutions 

 of all were green and much brown powder remained. In 1 

 the amount of sodium peroxide used was not sufficient to 

 oxidize all of the manganese to MnOg, and since the result is 

 higher than the others the inference is that MnOg is formed 

 from MnO^ with absorption of heat. 



The mean of the second and third results is 2014° and for 55 

 grams of manganese it is 110,770°. Hence, for the heat of the 

 oxidation of manganese to MnOj plus the combination of the 

 trioxide with sodium oxide we have 



Mn + 3Na,0, = Na,MnO, + 2]Sra,0 = iio-8° 



3Na O + 30 = 3Na O, + 58-2<= 



Mn + 30 + Na,0 = Na^MnO, + 169-0° 



