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



Heat observed . _ 8957° 11525° 



" of oxidation of iron — 64 c — 64 c 



" " oxygen taken up — 90 c 



8893 c 11371° 



For 1 gram of tin .. 1112 c 1125 c 



The mean of the five results is 1124 ; the average for 119 

 grams of tin is 133756°. Evidently the tin from the sodium- 

 tin alloy is the common modification. 



Amorphous stannic oxide used in the next two experiments 

 was made by heating metastannic acid over a ring burner until 

 the weight was constant. Sulphur was used to give the tem- 

 perature requisite and to reduce the sodium peroxide to oxide. 



Stannic oxide, amorphous. .. 



" " -unchanged. . 



" " combined _ . . 

 Water equivalent of system. 

 Temperature interval . 



Heat observed . 



" of oxidation of iron _ . 

 " " " " sulphur. 



" " oxygen set free .... 



• 16 





17 



9-955 gi 



rams 



7-907 grams 



1-204 



u 



0-583 " 



8-701 



i( 



7-324 " 



2987- 



a 



2987' " 



2-500° 





2-337° 



7467 c 





6961 c 



— 48 c 





— 48° 



— 5271° 





— 527l c 



+ 75° 





+ 75 c 



2223 c 



1717 C 



255 c 





237 c 



For 1 gram of stannic oxide . 



The mean is 246 c and for 151 grams of amorphous stannic 

 oxide it is 37100°. 



Summary of results. 



Sn + 2 = Sn0 2 (crystalline) + 137200° 



Sn (crystalline) + O = SnO(crystailine) + ... 66200 c 



SnO(crystalline) + O = SnO.. (crystalline) + __ 71000° 



Sn0 2 (amorphous) = Sn0 2 (crystalline) + . 1700° 



2Na 2 2 + Sn = Na 2 Sn0 3 + Na.O + -- 133800° 



2Na 2 + 20 = 2Na 2 + . 38800° 



Na 2 + Sn + 20 = Na 2 Sn0 3 + 172600° 



Sn + 2 = Sn0 2 (crystalline) + .'_ 137200° 



Na 2 4- Sn0 2 (crystalline) — Na 2 Sn0 3 + 35400° 



Na 2 + Sn0 2 (amorphous) = Na 2 Sn0 3 + 37100° 



