410 PROCEEDINGS OF THE AMERICAN ACADEMY. 



The Effect of Temperature on the Total Volume of Gas 



OCCLUDED BY ZlNCIC OxiDE. 



First Series : Heated Three Hours. 



(34) 1 gram of ZnO, after heating 3 hours at 660° ±, gave 0.365 c.c. gas. 



(35) " - " « " 0.380 " 



Average 0.373 c c. gas. 



(36) 1 gram of ZnO, after heating 3 hours at 750^ ±, gave 0.233 c.c. gas. 



(37) " " " " 0.210 " 



Average 0.221 c.c. gas. 



(38) 1 gram of ZnO, after heating 3 liours at 880° ±, gave 0.14 c.c. gas. 



(39) " « " « 0.18 " 



Average 0.16 c.c. gas. 



Second Series : Heated Thirty Minutes. 



(40) 1 gram of ZnO, after heating i Iiour at 750° ±, gave 0.366 c.c. gas. 



(41) " " " " 0.320 " 



Average 0.343 c.c. gas. 



(42) 1 gram of ZnO, after heating \ hour at 880°±, gave 0.192 c.c. gas. 



(43) " " " " 0.192 " 



Average 0.192 c.c. gas. 



Evidently, other conditions being equal, the total amount of gas 

 retained decreases very considerably as the temperature of ignition is 

 raised. Each one of these specimens of gas was anal3'zed, by means 

 of Hempel's apparatus modified for use on a small scale,* with interest- 

 ing results. The actual volume of nitrogen in every gram of material 



Figure 2. 



was found to be almost identical, diminishing only very slightly, if at all, 

 as the temperature increased, and amounting to about 0.14 cubic centi- 

 meters. Thus the lar<ze differences in the total volumes are due almost 

 wholly to oxygen., whicli varied from over sixty per cent in the first 



* The most important modification was the arrangement for connecting pipette 

 to burette. By blowinij and drawing down tlie capillary it maj' be made to fit so 

 perfectly into the fine rubber tube as to malie tlie loss of small bubbles impossible. 

 The diagram will make the idea clear. (Fig. 2 ) 



