ATOMIC WEIGHTS 335 



Popper's figiires give in mean Sb = 121.15. 



The recent investigations by Cohen and Strengers ' seem to prove 

 that these electrolytic determinations are worthless. They effected the 

 simultaneous precipitation of silver and antimony, using solutions of 

 SbClg, and found that the apparent atomic weight of antimony increased 

 with the concentration of the solutions. They give the results of 24 

 determinations, with full details, but only the end results need be cited 

 here: 



With 2.3 grm. SbClj in 100 cc. of solution, Sb = 120.84 to 120.87 

 " 83.3 " Sb = 121.81 to 121.92 



These values are calculated with old values for CI and Ag, but they 

 show the failure of the process to yield trustworthy figures. In any 

 final discussion of the atomic weight of antimony, therefore, the work 

 of Pfeifer and Popper must be disregarded. 



The work done by Bongartz "" in 1883 was quite different from any of 

 the determinations which had preceded it. Carefully purified antimony 

 was weighed as such, and then dissolved in a concentrated solution of 

 potassium sulphide. From this, after strong dilution, antimony trisul- 

 phide was thrown down by means of dilute sulphuric acid. After 

 thorough washing, this sulphide was oxidized by hydrogen peroxide, by 

 Classen's method, and the sulphur in it was weighed as barium sulphate. 

 The ratio measured, therefore, was 2Sb : 3BaS04, and the data were as 

 follows. The BaS04 equivalent to 100 parts of Sb is the ratio stated: 



Mean, 290.306, ± .0436 



Hence Sb = 120.61. 



^ Proc. Amsterdam Acad., Section of Sciences, 5 (2), 543. 1903. See also Cohen, Collins am 

 Strengers, Zeitsch. phys. Chem., 50, 291. 

 = Ber. Deutsch. chem. Ges., 16, 1942. 1883. 



