ATOMIC WEIGHTS 317 



error. These need not be rediscussed here, as the discussion would have 

 no value for present purposes; suffice it to say that in the series repre- 

 senting the oxidation of SboOg with the dichromate and chlorate, the 

 material used was found to be impure. Upon estimating the impurity 

 and correcting for it, the earlier value of Sb = 123.80 becomes Sb = 122.36, 

 according to Kessler's calculations. 



In the paper now under consideration four series of results are given. 

 The first represents experiments made upon a pure antimony trioxide 

 which had been sublimed, and which consisted cf shining colorless needles. 

 This was dissolved, together with some potassium chlorate, in hydro- 

 chloric acid, and titrated with dichromate solution. Six experiments 

 were made, but Kessler rejects the first and second as untrustworthy. 

 The data for the others are as follows : 



From these figures Kessler deduces Sb = 122.16. 



These data, reduced to a common standard, give the following quanti- 

 ties of oxygen needed to oxidize 100 parts of SbgOg to SboOg. Each cubic 

 centimetre of the KoCroO- solution corresponds to one milligranime of : 



10.985 

 10.939 

 10.951 

 10.936 



Mean, 10.953, ± .0075 



Hence Sb = 122.08. 



In the second series of experiments pure antimony was dissolved in 

 hydrochloric acid with the aid of an unweighed quantity of potassium 

 chlorate. The solution, containing both antimonious and autimonic 

 compounds, was then reduced entirely to the antimonious condition by 

 means of stannous chloride. The excess of the latter was corrected with 

 a strong hydrochloric acid solution of mercuric chloride, then, after 

 diluting and filtering, a weighed quantity of potassium chlorate was 

 added, and the titi-ation with dichromate was performed as usual. Cal- 

 culated as above, the percentages of oxygen given in the last column 

 correspond to 100 parts of antimony: 

 21 



