206 THE ATOMIC WEIGHTS. 



1.2425 grm. gave .400 SO 3 . (1.1656 grm. BaSO 4 .) 



1.138 " .366 " (1.0665 " ) 



.734 .2306 ( .6720 ) 



The figures in parentheses are reproduced by myself from Delafon- 

 taine's results, he having calculated his analyses with O = 100, S = 200, 

 and Ba = 857. These data may be reduced to a common standard, so 

 as to represent the quantity of 2Th(S0 4 ) 2 .9H 2 0, equivalent to 100 parts 

 of BaS0 4 . We then have the following results : 



106.597 

 106.704 

 109.226 



Mean, 107.509, .585 



Delafontaine was soon followed by Hermann,* who published a single 

 analysis of the lower hydrated sulphate, as follows : 



Th0 2 52.87 



S0 3 32.11 



H 2 15.02 



IOO.OO 



Hence, from the ratio between S0 3 and Th0 2 , Th0 2 = 262.286. Prob- 

 ably the S0 3 percentage was loss upon calcination. 



Both Hermann's results and those of Delafontaine are affected by one 

 serious doubt, namely, as to the true composition of the lower hydrated 

 sulphate. The latest and best evidence seems to establish the fact that 

 it contains four molecules of water instead of four and a half,f a fact 

 which tends to lower the resulting atomic weight of thorium consid- 

 erably. In the final discussion of these data, therefore, the formula 

 Th(S0 4 ) 2 .4H 2 will be adopted. As for Hermann's single analysis, his 

 percentage of Th0 2 , 52.87, may be included in one series with Delafon- 

 taine's, giving a mean of 52.535, .0473. 



The next determinations to consider are those of Cleve,J whose results, 

 obtained from both the sulphate and the oxalate of thorium, agree ad- 

 mirably. The anhydrous sulphate, calcined, gave the subjoined per- 

 centages of thoria : 



62.442 



62.477 



62.430 



62.470 



62.357 

 62.366 



Mean, 62.423, .014 



* Journ. fur Prakt. Chetn., 93, 114. 



t See Hillebrand, Bull. 90, U. S. Geol. Survey, p. 29. 



I K. Sveuska Vet. Akad. Handling., Bd. 2, No. 6, 1874. 



