206 THE ATOMIC WEIGHTS. 



1.2425 grm. gave .400 SO3. (1.1656 grm. BaSO^.) 



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(SOJ,.9H20, equivalent to 100 parts 

 of BaSO^. We then have the following results : 



106.597 

 106.704 

 109.226 



Mean, 107.509, =b .585 



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

 analysis of the lower hydrated sulphate, as follows : 



ThO, 52.87 



SO3. 32.11 



H2O 15.02 



100.00 



Hence, from the ratio between SO3 and ThO,, ThO, = 262.286. Prob- 

 ably the SO3 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,t 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(SOJa.4H20 will be adopted. As for Hermann's single analysis, his 

 percentage of ThO.^, 52.87, may be included in one series with Delafon- 

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



The next determinations to consider are those of Cleve,t 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. fiir Prakt. Chem., 93, 114. 



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



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



