M. Delafontaine on Thorium and its Oxide. 229 



centrated and heated in the water-bath to 100°, by which a sul- 

 phate of thoria little soluble in hot water was deposited. This 

 operation was repeated several times, and the precipitate was 

 considered to be pure when, on heating*, it left a perfectly white 

 residue. The mother-liquor from all these crystallizations, on 

 the addition of sulphate of potash, yielded the thoria in them in 

 the form of double salt. 



The sulphate of thoria thus obtained is heavy, white, and 

 caseous ; it consists of a large number of very small interlaced 

 needles, which gave to it a porcelain-like appearance. In no 

 case could distinct crystals be seen ; but when on this salt was 

 poured a quantity of water insufficient for its solution, it became 

 converted into clear colourless crystals in the form of 6 to 8-sided 

 prisms with pointed ends. 



These two compounds differ in the quantity of water they 

 contain. The water in them was determined by heating them 

 from 400° to 450°, and the thoria by heating the salt to redness 

 until the weight remained constant. To determine the sulphuric 

 acid, the thoria was first precipitated as oxalate, and in the 

 filtrate the sulphuric acid was precipitated by chloride of barium, 

 hydrochloric acid having been previously added. 



The results of Delafontaine ; s analysis show that if thoria is to 

 be considered as a base, ThO, the salts must have respectively 

 the improbable formulae 4RO S0 8 + 9Aq and 2 ThO S0 8 + 9Aq. 

 But some time ago* Norclenskiold and Chydenius showed that 

 crystallized thoria prepared in the dry way had the same form 

 and angles as stannic and titanic acids. This, then, seems to show 

 that thoria, likezirconia, which it so much resembles, consists of 

 one atom of metal and two of oxygen; if, then, this is the case, 

 the above salts have the formulae 



2Th0 2 S0 3 + 9Aq 

 and 



Th0 2 S0 3 + 9Aq. 



The objection that the water in the first salt is expressed by a 

 fraction, it shares with the sulphates of uranium, cadmium, 

 yttrium, and didymium. The atomic weight of thorium is then 

 231-5. 



St. -Claire Deville and Troostf have made the following expe- 

 riment, which shows that iron is permeable to hydrogen gas at 

 a high temperature. A tube of cast steel was taken containing 

 so little carbon that it could not be hardened, and so soft that it 

 could be drawn out in the cold to a tube of 3 to 4 millimetres in 



* Phil. Mag. vol. xx. p. 375 

 t Comptes Benches, vol. lvii. 



p. 9GG. Liebig's Annalen, May 1864. 



