180 THE ATOMIC WEIGHTS. 



TELLURIUM. 



Particular interest attaches to the atomic weight of tellu- 

 rium, on account of the speculations of MendelejefF. Ac- 

 cording to the " periodic law " of that chemist, tellurium 

 should lie between antimony and iodine, having an atomic 

 weight greater than 120, and less than 127. Theoretically, 

 Mendelejeff assigns it a value of Te = 125; but all the 

 published determinations lead to a mean number higher 

 than would be admissible under the aforesaid " periodic 

 law." Whether theory or experiment is at fault remains to 

 be discovered. 



The first, and for many years the only, determinations of 

 the constant in question, were made by Berzelius.* By 

 means of nitric acid he oxidized tellurium to the dioxide, 

 and from the increase in weight deduced a value for the 

 metal. He published only his final results ; from which, if 

 O = 100, Te = 802.121. The three separate experiments 

 give Te = 801.74, 801.786, and 802.838 ; whence we can cal- 

 culate the following percentages of metal in the dioxide : 



80.057 

 80.036 

 80.034 



Mean, 80.042, i .005 



The next determinations were made by von Hauer,t who 

 resorted to the analysis of the well crystallized double salt 

 TeBr4.2KBr. In this compound the bromine was estimated 

 as silver bromide, the values assumed for Ag and Br being 

 respectively 108.1 and 80. Recalculating, with our newer 

 atomic weights for the above named elements, we get from 

 V. Hauer's analyses, for 100 parts of the salt, the quantities 

 of AgBr which are put in the third column : 



* Poggend. Annal., 28, 395. 1833. 

 f Sitzungsb. Wien Akad., 25, 142. 



