W. G. Mixter—Heat of Oxidation of Tin. 233 



For 1 gram of oxygen con- 

 sumed .___ 4423 c 4401° 4443° 



" 1 gram of SnO in sub- 

 stance taken 521 c 522° 521 c 



The average is 4417° for one gram of oxygen and for 16 grams 

 it is 70672° at constant pressure and 71000° at constant volume. 

 The mean for one gram of SnO in the substance taken is 

 521 c ; for 135 grams 70335° at constant volume. Evidently 

 the stannous oxide was nearly all burned to stannic oxide. 

 Andrews' result was 69000 at constant pressure. 



Combustion of Tin with Sodium Peroxide. 



The metal used in the next three experiments was from the 

 same lot taken for experiments 1 and 2 and prepared from the 

 sodium-tin alloy. Carbon was added to the mixture in experi- 

 ment 10 to ensure a high temperature, but it was not required, 

 as the other experiments prove. JSTo metallic tin was found in 

 the residues of the following determinations : 



11 12 13 



Tin... _.. 3-000 5-000 8-000 grams 



Carbon 0-330 " 



Sodium peroxide 10- 10- 18* " 



Water equivalent of system 3060- 3012- 2987" " 



Temperature interval 2-283° 1*871° 3-086° " 



Heat observed . 6986° 5635° 9218° 



" of oxidation of carbon —3663° 



" " " " iron.. —30° —30° —40° 

 " " oxygen set free or 



taken up +46° —48° -f 



! V 



3339° 5617° 9260° 



For 1 gram of tin 1113° 1115° 1157° 



As the tin from the sodium-tin alloy gave more heat when 

 burned with exygen than that known to be the common modi- 

 fication, tin turnings were made by fastening a cylinder of 

 tin in a lathe so that it rattled. Small chips came off which 

 were separated from the coarser process by sifting. The 

 following are the experimental data : 



14 15 



Tin 8*241 grams 10*175 grams 



" not burned 0-243 ". 0-064 " 



" burned ._.„ 7*998 " 10-111 " 



Sodium peroxide 22* " 25* " 



Water equivalent of system. __ 3759* " 3816* " 



Temperature interval 2*383° 3*020° 



