28 W. G. Mixter — Polymerization of Oxides. 



For this purpose the preparation designated as E was made as 

 follows : a portion of D (which was a soft red powder con- 

 taining 2 - 6 per cent of water) was heated vejy gradually to 

 approximately 1000°* and then kept at this temperature two 

 hours. The oxide resulting was in the form of a dark gray 

 friable mass. It was easily rubbed to a powder and was 

 passed through a mesh less than 1/200 of an inch. The 

 powdered oxide, after heating twice as described, showed no 

 change in appearance and each time formed a coherent mass. 

 It was found not to change weight during the last heating 

 and to be free from ferrous oxide. The dark gray powder 

 turned dark red when finely ground. It was not too coarse 

 for the calorimetric experiments. The mean of the results for 

 E is 361 cal. This does not indicate polymerization of ferric 

 oxide between a dull red heat and 1000°. 



The results obtained with ferric oxide holding various 

 amounts of water are given in considerable detail in Table II, 

 as they show that the experimental errors are probably small. 

 The values obtained for D and A 2 are the best because of the 

 purity of the preparations used, and only these values will be 

 discussed. The mean for D is 425 and for A 2 is 529. The 

 2*6 per cent of water is undoubtedly more firmly held by the 

 ferric oxide than the ll - 6 per cent. If it is assumed that the 

 heat of combination of 1 g. of water in both A and D is the 

 same, the error will not be great, for the proportion of water in 

 D is small. Furthermore, it is assumed that the ferric oxide is 

 in the same molecular state in both D and A 2 . Then if x equals 

 the heat effect of 1 g. of ferric oxide in the fusions and y that 

 of 1 g. of water combined with the ferric oxide, we have 



0-974:*: + 0-026?/ = 425 

 0-884a; + 0*1 16y = 529 



x — 398 Cal. for 1 g. of ferric oxide. The heat of fusion of 

 18 g. of water is 1*44 Cal. and 36-1 - 1-440 -r 18 = 1-9 Cal. for 

 the heat effect of 1 gr. of solid water reacting in the sodium 

 peroxide fusions. Assuming that in D the solid water is not 

 combined with heat effect, we have 



425 — (0-026 X 1-19 Cal. -=-) 0-974 = 385 cal. 



for 1 g. of ferric oxide. Hence, on any assumption the ferric 

 oxide in D which had been heated only to 160° polymerizes at 

 high temperatures. The difference between 398 and 363 is 

 35 cal. and for a gram molecule of ferric oxide, 160 g., it is 

 5-6 cal. 



* Silver, m. p. 960°, melted in the electric furnaces used, but gold, m. p. 

 1060°, did not melt. 



