528 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



To reduce these we have 8 = 32.0667, ±.00075, and H = 1.00779, ± 

 .0001. Hence, giving to the value from ratio 4 the arbitrary weight 

 represented by ±.075 — 



From ratio 3 Sa r= 150.31G, ± .0095 



" 1 150.344, ± .0740 



" 5 150.473, ± .0221 



" 2 150.483, ± .0124 



" 4 150.666, ± .0750 



General mean, Sa = 150.390, ± .0071 



The average from the determinations by Urbain and Lacombe is Sa = 

 150.46. The roiinded-off fignre 150.4 is probably near the truth, with 

 an actual uncertaintv as lars^e as 0.1. 



ETJROPIUM. 



Demargay," the discoverer of europium, found for its atomic weight 

 the approximate number 151. The first detailed determinations, how- 

 ever, were those of Urbain and Lacombe," who analyzed the octohydrated 

 sulphate. I give their weights, and three percentage columns, as follows : 

 A, Eu^CSOJ;; in Eu,(SOj3.8H.,0. B, Eu.Og in Eu,(S0,),.8H„0. C, 

 EuoOg in Eu,,(S04)3. 



Eu,iS0,)^.8HX). Eii.(SO,)s. Eu.O^. A. B. C. 



Jantsch ^ determined the atomic weight of europium by calcination of 

 the hydrous sulphate : 



'Compt. Rend., 132, 14S4. 1900. 

 *Compt. Rend., 138, 627. 1904. 

 ^Coinpt. Rfiul., 146, 473. 1908. 



