ATOMIC WEIGHTS 



275 



Mean, 130.3910,±.00034 



Hence Tl = 204.041. 



Lepierre's ' deterrainations were published in 1893, and represented 

 several distinct methods. First, thallous sulphate was subjected to elec- 

 trolj'sis in presence of an excess of ammonium oxalate, the reduced metal 

 being dried and weighed in an atmosphere of hydrogen. The corrected 

 weights, etc., are as follows: 



1.8935 grm. TLSO4 gave 1.5327 Tl. 80.945 per cent. 

 2.7243 " 2.2055 " 80.957 



2.8112 " 2.2759 " 80.958 



Mean, 80.953, ± .0030 



Hence Tl = 204.150. 



Secondly, weighed quantities of crystallized thallic oxide were con- 

 verted into thallous sulphate by means of sulphurous acid, and the 

 solution was then subjected to electrolysis, as in the preceding series. 



3.2216 grm. TLO3 gave 2.8829 Tl. 89.487 per cent. 



2.5417 " 2.2742 " 89.475 



Mean, 89.481, ± .0040 



Hence Tl = 204.158. 



In the third set of experiments a definite amount of thallous sulphate 

 or nitrate was fused in a polished silver crucible with ten times its weight 

 of absolutely pure caustic potash. Thallic oxide was thus formed, which, 

 with various precautions, was washed with water and alcohol, and finally 

 weighed in the original crucible. One experiment with the nitrate gave — 



2.7591 grm. TINO3 yields 2.3649 TLOs- 85.713 per cent. 



Hence Tl = 204.037. 



1 Bull. Soc. Chim. (3), 9, 166. 



