ATOMIC WEIGHTS 40:3 



It has already been stated that several of the more important investi- 

 gations relative to the atomic weight of tellurium, have had for their 

 purpose the establishment of its homogeneity. Up to this point all the 

 evidence has gone to show that it is not a mixture of two elements. 

 Tellurium from widely different sources, as in Lenher's recent work, 

 gives one and the same value for its atomic weight. Fractionations by 

 different methods have also given constant results, and it seemed as if 

 the question had been definitely settled. Very recently, however, even 

 since this chapter was in great part written. Browning and Flint ' have 

 secured evidence upon the other side, which deserves some attention. 

 When tellurium tetrachloride is mixed with water and hydrolyzed, a 

 large part of it is precipitated as tellurium dioxide. A part, however, 

 remains in solution, from which it can be thrown down by ammonia 

 and a slight excess of acetic acid. Carefully purified tellurium was 

 treated by the process thus briefly suggested, and converted, with all due 

 precautions, into the basic nitrate. The portion precipitated by hydrolv- 

 sis gave, on analysis of the nitrate, a mean value of Te = 136.53. From 

 the portion afterwards thrown down the value 128.97 was obtained. 

 Otlrer determinations, by other methods, gave similar results. The alplia, 

 or first precipitate, gave mean values, in two additional series, of 126.64 

 and 126.31. The heta portion, that not precipitated during hydrolysis 

 of the chloride, gave Te = 128.77 and 128.81. Browning and Flint intend 

 to continue their research; but until that is finislied it is not practicable 

 to discuss their atomic weights in connection with previous determina- 

 tions. Their fractionations are evidently not perfect, but preliminary; 

 and their atomic weights are not given as being anything more than 

 approximations. So far they have established a reasonable probability; 

 nothing more. 



1 Amer. Joiirn. Sci. (4), 28, 347. 1909. 



