234 THE ATOMIC WEIGHTS. 



H^O. SOy La^Oy La^O.^ in anhydrous salt. 



22.570 33-333 44-090 56.947 



22.610 33- 160 44.240 57-150 



22.630 33-051 44-310 57-277 



Mean, 57.021, ± .051 



Erk * found that .474 grm. of La 2 (804)3, by precipitation 

 as oxalate and ignition, gave .2705 grm. of La 2 3, or 57.068 

 per cent. .7045 grm. of the sulphate also gave .8815 grm. 

 of BaS04. Hence 100 parts of BaS04 are equivalent to 

 79.921 of La 2(804)3. 



Last of all, and probabl}'^ best of all, we come to the de- 

 terminations of Cleve.f 8trongly calcined LajOg, spectro- 

 scopically pure, was dissolved in nitric acid, and then, by 

 evaporation with sulphuric acid, converted into sulphate : 



1. 9215 grm. La203 gave 3.3365 grm. sulphate. 57.590 per cent. 



2.0570 " 3-5705 " 57-611 



1.6980 " 2.9445 " 57-667 " 



2.0840 " 3.6170 " 57-617 " 



1.9565 " 3-3960 " 57-612 " 



Mean, 57.619, it .0085 



From the last column, which indicates the percentage of 

 La^Og in La(804)3, we get, if 8O3 = 80, La = 139.15. 



We may now combine the similar means into general 

 means, and deduce a value for the atomic weight of lantha- 

 num. For the percentage of oxide in sulphate we have six 

 estimates, as follows. The single experiments of Czudnowicz 

 and of Erk are assigned the probable error and weight of a 

 single experiment in Hermann's series : 



Czudnowicz 58.668, ±.027 



Erk 57.068, zh .027 



Hermann 57.654, ±.016 



Zschiesche 57.021, it .051 



Marignac _" 57-5475. ± -0115 



Cleve 57.619, ±.0085 



General mean 57.620, it .0059 



* Jenaisches' Zeitschrift, 6, 306. 1871. * 



t K. Svenska Vet. Akad. Handlingar, Bd. 2, No. 7. 1874. 



