ATOMIC WEIGHTS 391 



it exists as an impurity. This difference of origin in tlie material studied 

 gives the chief interest to the investigation. The data are as follows : 



Mean, 103.633, ± .0023 

 Brauner found, 103.644, ± .0018 



General mean, 103.640, ± .0014 



From Chikashige's mean, Te = 127.43. 



Metzner ' determined the atomic weight of tellurium by two methods, 

 using tellurium which had been prepared from the hydride. First, 

 tellurium was treated with sulphuric acid and converted into the basic 

 sulphate, TCaSO^. I give his weights, and also the percentage of tellurium 

 in the compound : 



Mean, 63.978, ± .0040 



Hence Te = 127.94. 



Secondly, Metzner prepared tellurium dioxide by hydrolysis of the 

 tetrachloride, and reduced it to tellurium by heating in a current of 

 carbon monoxide. The reduction was effected in presence of silver, in 

 order to avoid volatilization. His data follow, with the usual percentage 

 of Te in TeOj stated in the third column : 



TeO„. 



743.2 

 1106.7 



988.5 

 1312.5 



Mean, 80.004, ir: .0165 



Hence Te = 128.032. 



The determinations by Heberlein ' represent three distinct methods, 

 starting with crystallized telluric acid, H^TeOe. First, the acid was 

 treated with hydrochloric acid, by which chlorine was liberated. The 



^ Compt. Rend., 126, 1716. 1898. Metzner fails to state what his weiglits- mean. Are they 

 milligrammes? 

 - Inaug. Diss., Basel. Printed at Strassburg, 1898. — !i:iti 



