276 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



Two experiments were made with the sulphate, as follows: 



3.1012 grm. TLSO^ gave 2.8056 TI2O3. 90.408 per cent. 

 2.3478 " 2.1239 " 90.4C3 



Mean, 90.465, ± .0020 



Hence Tl = 304.021. 



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. Tl^Oj gave .3301 HjO. 11.843 per cent. 



3.9871 " .4716 " 11.828 



4.0213 " .4761 " 11.839 



Mean, 11.837, ± .0029 



Hence Tl = 204.300. 



In a supplementary note^ Lepierre states that his weights were all 

 reduced to a vacuum standard. 



Some work by Wells and Penfield,'' 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 

 the series, were both converted into chloride. In the latter the chlorine 

 was estimated as silver chloride, which was weighed on a Gooch filter, 

 with the results given lielow, which are sensibly identical. The TlCl 

 equivalent to 100 parts of AgCl is stated in the last column. 



TlCl. AgCl. Ratio. 



Crystals 3.9146 2.3393 167.341 



Mother liquor 3.3415 1.9968 167.343 



Mean, 167-.342 



Hence Tl = 204.41. 



The general mean of Lamy's and Hebberling's determinations of this 

 ratio gave IGG. 555, ±.0865. If we arbitrarily assign Wells and Pen- 

 field's mean equal weight with that, we get a new general mean of 

 166.948, It .0610. 



1 Bull. Soc. Chim. (3), 11, 423. 1S94. 

 «Ainer. Journ. Sci. (3), 47, 466. 1894. 



