24 W. G. Mixter — Polymerization of Oxides. 



15"5 + 19*4: = 34*9 for the heat of combination of sodium 

 oxide with water. Beketoff, however, found that ]STa 2 4- aq 

 — 55'5 and Rengade, 56*5. The mean 56 — 19*9 (the heat of 

 solution of 2NaOH), = 36-1 for the heat effect of Na s O + 

 H 2 0. It is impossible to say which is the better one of the 

 two values, but 36 - l accords best with the results obtained with 

 gypsum and brucite and is the one used in this paper. 

 When a combustible substance, such as sulphur or carbon, is 

 mixed with the peroxide and an hydroxide, and the mixture 

 ignited, sodium oxide is formed thus : 



S + 3Na 2 2 = Na 2 S0 4 + 2¥a 2 



and the sodium oxide unites with the combined water to form 

 hydroxide. If the mixture contains brucite the reaction 

 then is 



S + 3Na 2 2 + MgO.H 2 = Na 2 S0 4 + MgO + 2NaOH + Na 2 

 and the heat effect in excess of that due to the sulphur is 

 (Na 2 + H„0) - (MgO + H 2 0) 



The method of fusion with sodium peroxide on hydrates was 

 first tried with hydrous calcium sulphate because Thomsen 

 found the heat of combination of water with anhydrous calcium 

 sulphate. For the work CaS0 4 .2H 2 was precipitated from a 

 cold solution of calcium chloride by sulphuric acid. After 

 standing a day it was washed and dried over oil of vitriol in a 

 vacuum. It lost on heating 20 - 9 per cent ; calculated for 

 2H 2 0, 2G"9 per cent. The anhydrous sulphate used in experi- 

 ments 1 and 2 was obtained by heating the hydrous salt at 160° 

 until the weight was constant, while that used in experiment 3 

 was heated to 200°. In experiments 4 and 6 the CaS0 4 .2H 2 

 made was used, and in 5 a good specimen of selenite. It 

 was impossible to mix thoroughly by shaking together in the 

 bomb, sulphur, the precipitated CaS0 4 .2H 2 and sodium perox- 

 ide. The fine sulphur apparently was electrified, for some of 

 it adhered to the bomb and did not burn completely when the 

 fusion occurred. In some experiments a little free sulphur 

 remained, and in all cases where the mixtures were made in the 

 bomb the results were low and considerable silver sulphide was 

 formed. The mixture for experiments 3 and 5 were made in a 

 mortar. In 3 and 6 lampblack was used in place of sulphur 

 and the mixing was made by shaking the ingredients in the 

 bomb closed by a glass plate. The experimental data are 

 given in Table I. 



The mean of 1, 2 and 3 for CaS0 4 is 323 cal., which gives 

 437 Cal. for 1 gram molecule. It was found that calcium 



