414 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Siuce so many circumstances regulate both the amount of gas and 

 its composition, one is not surprised that Morse and Arbuckle obtained 

 varying mixtures with eight different preparations of zincic oxide. It 

 is true tliat their expulsion of the gases continued until it had become 

 so slow that two successive weighincrs with intermediate heating nave 

 constant weight ; but the same causes of change must still have been 

 at work, although far more slowly. 



In the light of these interesting results, it seemed worth while to 

 make a more elaborate investigation of the relation of the composition 

 of the gases held by cwpric oxide to the temperature used in its ignition. 

 The material used in the following determinations was the soft powder 

 made by the decomposition of cupric nitrate at 280°. 



The Effect of Temperature of Igxition on the Composition 

 OF Gases retained by Cupric Oxide. 



Time of Ignition^ 1 hour. 



(63) 0.32 c.c. gas from 1 gr. CuO heated at 520^ contained 18 per cent oxygen. 



(64) 034 " " " " 15 



Average 15.5 per cent oxygen. 



(65) 0.49 c.c. gas from 1 gr. CuO heated at 660° contained 6 per cent oxygen. 



(66) 0.48 " " " " 5 



Average 5.5 per cent oxygen. 



(67) 0.47 c.c. gas from 1 gr. CuO heated at 750° contained 3 per cent oxygen. 



Average 3.5 per cent oxygen. 



0.05 c.c. gas from 1 gr. CuO heated at 1000° ± contained to 4 per cent oxygen, 

 according to Alexander Scott. 



It is evident that the cupric nitrate remaining in the cupric oxide had 

 not been wholly decomposed by heating for an hour at 500° (experi- 

 ments No. 63 and 64) and that we are dealing here with an increasing 

 total, and a maximum similar in every respect to that already noted 

 in the case of zinc,* except that in the present case more nitrogen 

 is held, while the oxygen escapes at a much lower temperature. 



* See page 412. 



