RICHARDS. — RETENTION AND RELEASE OP GASES. 411 



average, to less than twenty per cent in the third. The small amount 

 of carbon dioxide present was absorbed almost completely by the boiled 

 water over which the gases were collected ; hence it need not be con- 

 sidered.* The actual volumes of nitrogen in the five averages were 

 respectively 0.138, 0.133, 0.130, in the first series, and 0.152 and 0.127 

 in the second series ; while the actual amounts of oxygen were respect- 

 ively 0.235, 0.087, 0.030 in the first series, and 0.191 and 0.065 in the 

 second. No better proof could be desired of the fact that zincic oxide 

 allows its oxygen to depart more easily than its nitrogen. These 

 results are wholly confirmatory of the results of Richards and Rogers 

 already mentioned; but of course they do not explain how Morse and 

 Arbuckle, working at nearly constant temperature, obtained inconstant 

 results. To accomplish this explanation, the other possible causes 

 affecting the retention of gases must be considered. 



The Effect of Time of Ignition on the Amount of Gas 



RETAINED BY ZiNCIC OxiDE. 



First Series : Just above the Melting Point of Thallous Sulphate. 



(44) 1 gram of ZnO, heated at 660^ for 1 liour, gave 46 c.c. gas. 



(34) 1 gram of ZnO, heated at 660° for 3 hours, gave 0.36 c.c. gas. 



(35) « « " 0.38 " 



Average 0.37 c.c. gas. 



Second Series : Just above the Melting Point of Potassic Chloride. 



(45) 1 gram of ZnO, heated at 750° for 10 minutes, gave 0.27 c.c. gas. 



(46) 1 gram of ZnO, heated at 750° for 20 minutes, gave 0.35 c.c. gas. 



(40) 1 gram of ZnO, heated at 750° for 30 minutes, gave 0.37 c.c. gas. 



(41) " " « 0.32 " 



Average 0.35 c.c. gas. 



(47) 1 gram of ZnO, heated at 750° for 60 minutes, gave 0.30 c.c. gas. 



(48) " " " 0.32 " 



Average 0.31 c.c. gas. 



(36) 1 gram of ZnO, heated at 750° for 180 minutes, gave 0.21 cc. gas. 



(37) " " « 0.25 " 



Average 0.23 c.c. gas. 



* Tiiese Proceedings, XXVIII. 205, 209. In a number of cases where pains 

 was taken to measure the carbon dioxide, its volume never exceeded three or 

 four per cent, and was usually about two per cent. 



