386 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



TELLUEIUM. 



Particular interest attaches to the atomic weiglit of tellurium on ac- 

 count of its relations to the periodic system. According to that system, 

 tellurium should lie between antimony and iodine, having an atomic 

 weight greater than 120 and less than 126. Theoretically, Mendeleef 

 assigns it a value of Te = 125, but all of the best determinations lead to 

 a mean number higher than is admissible under the currently accepted 

 hypotheses. 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 = 100, Te = 802.121. The three separate experiments give Te = 

 801.74, 801.786 and 802.838, whence we can calculate the following per- 

 centages of metal in the dioxide : 



80.057 

 ■ 80.036 



80.034 



Mean, 80.042, ± .005 



Hence Te = 128.34. 



The next determinations were made by von Hauer,° wlio resorted to 

 the analysis of the well crystallized double salt TeBr^.2KBr. In this 

 compound the bromine was estimated as silver bromide, the values 

 assumed for Ag and Br being respectively 108.1 and 80. Eecalculating, 

 we get from von Hauer's analyses, for 100 parts of the salt, the quantities 

 of AgBr which are put in the third column : 



2.000 grm. K.TeBrs gave 69.946 per cent. Br. 1C4.4G0 



6.668 " 69.8443 " 164.221 



2.934 " 69.9113 " 164.379 



3.697 " 70.0163 " 164.626 



1.000 " 09.901 " 164.355 



Mean, 164.408, ± .045 

 Hence Te= 127.64. 



Dumas,* by a method for which he gives absolutely no particulars, 

 found Te = 129. 



' Poggend. .■Xnnalen, 28, 395. 1833. 

 - Sitzungsb. Wien. Akad., 25, 142. 

 'Ann. Chim. Pliv*. rS). 55, 129. 1859. 



