186 THE ATOMIC WEIGHTS. 



Lepierre's* determinations were published in 1893, and represented 

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

 trolysis in presence of an excess of ammonium oxalate, the reduced 

 metal being dried and weighed in an atmosphere of hydrogen. The cor- 

 rected weights, etc., are as follows: 



J - 8 935 grm. T1 2 SO 4 gave 1.5327 Tl. 80.945 per cent. 



2.7243 " 2.2055 " 80.957 



2.8112 " 2.2759 " 80.958 " 



Mean, 80.953, =t .0030 



Secondly, weighed quantities of crystallized thallic oxide were con- 

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

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



3.2216 grm. T1 2 O 8 gave 2.8829 Tl. 89.487 per cent. 



2.5417 " 2.2742 " 89.475 



Mean, 89.481, =h .0040 



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. T1NO 3 yields 2.3649 T1 2 O 3 . 85.713 per cent. 



Two experiments were made with the sulphate, as follows : 



3.1012 grm. T1 2 SO 4 gave 2.8056 T1 2 O 3 . 90.468 per cent. 



2.3478 " 2.1239 " 90-463 " 



Mean, 90.465, .0020 



Finally, crystallized thallic oxide was reduced by heat in a stream of 

 hydrogen, and the water so formed was collected and weighed. 



2.7873 grm. T1 2 O 3 gave .3301 H 2 O. 11.843 P er cent - 



3.9871 " .4716 " 11.828 " 



4.0213 " .4761 " 11-839 " 



Mean, 11.837, d= .0029 



Iii a supplementary notef Lepierre states that his weights were all 

 reduced to vacuum standards. 



Some work by Wells and Penfield, J incidentally involving a deter- 

 mination of atomic weight, but primarily intended for another purpose, 

 may also be taken into account. Their question was as to the constancy 

 of thallium itself. The nitrate was repeatedly crystallized, and the last 

 crystallization, with the mother liquor representing the opposite end of 



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

 fBull. Soc. Chim. (3), n, 423. 1894. 

 J Amer. Journ. Sci. (3), 47, 466. 1894. 



