272 THE ATOMIC WEIGHTS. 



of Berzelius and von Hauer were employed, with various rigid precau- 

 tions in the way of testing balance and weights, and to ensure purity of 

 material. In the first series of experiments tellurium was oxidized by 

 nitric acid to form Te0 2 . The results gave figures ranging from Te = 

 125.64 to 128.66 : 



2.21613 grm. Te gave 2.77612 grm. TeO 2 . 79.828 per cent. Te. 



1.45313 1.81542 " 80.044 " 



2.67093 " 3-33838 " 80.007 



477828 " 5.95748 " 80.207 " 



2.65029 " 3-3I33 1 " 79-989 



Mean, 80.015, .041 



In the second series tellurium was oxidized by aqua regia to Te0 2 , with 

 results varying from Te == 127.10 to 127.32 : 



2.85011 grm. Te gave 3.56158 grm. TeO 2 . 80.024 per cent. Te. 



3.09673 3-86897 " 80.040 " 



5-93 6 5 " 6.36612 " 80.012 " 



3.26604 4.08064 " 80.037 " 



Mean, 80.028, .004 



By von Hauer's process, the analysis of TeBr 4 .2KBr, Will's figures give 

 results ranging from Te = 125.40 to 126.94. Reduced to a common 

 standard, 100 parts of the salt yield the quantities of AgBr given in the 

 third column : 



1.70673 grm. K 2 TeBr 6 gave 2.80499 grm. AgBr. 164.349 



1.75225 " 2.88072 " .164.398 



2.06938 " 3-40739 " 164.657 



3.29794 5-43 22 8 " 164.717 



2.46545 " 405742 " 164.571 



Mean, 164.538, .048 



Combined with von Hauer's mean, 164.408, .045, this gives a general 

 mean of 164.468, .033. Hence Te = 126.502. 



The next determinations in order of time were those of Brauner.* 

 This chemist tried various unsuccessful methods for determining the 

 atomic weight of tellurium, among them being the synthetic preparation 

 of -silver, copper, and gold tellurides, and the basic sulphate, Te 2 S0 7 . 

 None of these methods gave sufficiently concordant results, and they 

 were therefore abandoned. The oxidation of tellurium to dioxide by 

 means of nitric acid was also unsatisfactory, but a series of oxidations 

 with .aqua regia gave data as follows. The third column contains the 

 percentage of tellurium in the dioxide : 



* Journ. Chem. Soc., 55, 382. 1889. 



