120 ATOMIC WEIGHT DETERMINATIONS. 



203.026.] The salts were purified by recrystallization. 

 {LieUg's Ami., 134, 1865, 11.) 



W. Crookes : S04-.155 (0 = 16). 



Determined by experiments on the solution of metallic thal- 

 lium in nitric acid and evaporation to dryness. The number 

 is the mean of ten experiments; extreme difference, 0.038. 

 The balance stood in a partial vacuum, and the weighings 

 were made at two different pressures and calculated for 

 vacuum. Very elaborate precautions were taken through- 

 out. Crookes also mentions determinations made with 

 barium nitrate, but gives no data. The thallium was pre- 

 pared in seven different lots by the reduction of as many 

 different salts which had been purified by recrystallization 

 &c. The metal was fused in lime. The reagents were ex- 

 pecially prepared by methods similar to those of Stas. 

 Crookes took N = 14.009, = 15.96, and calculated for Tl 

 the value 203.642. [If O = 16, the value becomes 204.155.] 

 {PhU. Trans., 163, 1873, 277.) 



THOEIUM. 



From the isomorphism existing between thorium, tin, 

 and titanium, and from the similarity of thorium to zir- 

 conium, Delafontaine and Marignac believe the oxide to 

 contain two atoms of oxygen. {Llebig's Ann., 131, 100.) 

 Neither the specific heat of this element nor the vapor 

 density of any of its compounds has been determined so 

 far as I know. 



J. J. Berzelius; ^38 (P = 16); 1887.72 (0 = 100). 



From the sulphate, precipitated by heating a solution of 

 the salt and redissolved in cold water, Berzelius got the 

 values 748.493 and 735.713 by precipitating with barium 

 chloride, lie also analysed the double sulphate of potas- 

 sium and thorium. From the relation between the sul- 

 phuric acid and the thorium oxide found, the atomic weight 

 would seem to be 750.63, while the relation between the 

 potassic sulphate obtained, and the amount of oxide gives 

 740.6. These numbers are calculated on the supposition 

 that the oxide contains a single atom of oxygen. Ba = 



