146 REPORTS ON INVESTIGATIONS AND PROJECTS. 



sulphate gave 0.6001 gram oxide, atomic weight 227.3 ; 0-9745 gram sul- 

 phate gave 0.5973 gram oxide, atomic weight 221.5. If the four results 

 obtained by this method be compared, it is evident that it does not give satis- 

 factory results and that it can not be used for atomic weight determinations. 



The third possible method was used by Meyer and Gumperz. These 

 authors expressly state that only a crystallized sulphate gives exact results, 

 and that even among the various crystallized sulphates of thorium only those 

 with 8 and with 9 molecules of water of crystallization are suitable for the 

 determination, whereas the tetrahydrate yields unsatisfactory results. The 

 octo- (or ennea-) hydrate must be dried at 400° C, whereby neutral anhy- 

 drous sulphate is obtained. This is then converted into oxide and the calcu- 

 lations are made from the relation Th (SOJ, : ThO,. The authors say : ' ' Our 

 experiences have shown us that the method described here is the only one 

 which can be used for the preparation of a neutral anhydrous sulphate. ' ' 



In order to control this statement also in a positive way, crystallized 

 sulphate was prepared according to the directions given by Mej^er and 

 Gumperz. The evaporation of the sulphate solution was carried out at 

 ca. 35° C. in a round flask, constantly drawing dry air through the liquid, 

 in order to accelerate the evaporation. After about two-thirds of the liquid 

 had evaporated, a mass of very small, fine crystals separated out, which 

 were dried in the air without heating. 



The determination made with this substance gave the following results : 



1.4893 gram hydrate gave 1.2136 gram anhydride and 0.9326 gram oxide. 



The small quantity of water, which corresponds to only 18.51 percent, 

 shows that the substance obtained could not be the one which should have 

 been expected. The atomic weight of the element contained in it, assuming 

 the formula M(SO02 for the anhydrous sulphate, would be as high as 499. 

 Such a figure is altogether out of question. The compound must, there- 

 fore, have a different composition. Assuming 256 as atomic weight of the 

 metal contained in it, a simple formula can not be constructed, but on the 

 basis of 232 for that figure the formula ThSO^O ; 4.5H,,0 is found. 



The compound, according to the figures given above, contains 62.62 per 

 cent ThO,, 18.86 per cent SO,, 18.51 per cent H^O. By dividing these 

 numbers by the molecular weights respectively, we obtain the relation 

 0.237 : 0.237 : 1.028, which is equivalent to i.oo : i.oo : 4.34. The quantity 

 of water found by this analysis is, therefore, a little smaller than required 

 by the formula given above. 



The correctness of the formula was confirmed by a direct analysis, made 

 in the following way : 0.5453 gram of the substance was dissolved in water, 

 the thoria precipitated with ammonia and the sulphuric acid determined in 

 the filtrate by means of barium chloride 0.3353 gram ThO^ and 0.3015 gram 

 BaSOi were thus obtained. 



