OF ARTS AND SCIENCES. 5 



whose atomic weights he redetermined, his process consisted in analyz- 

 ing the chloride (SbCl.j) and weighing the chlorine as argentic cliloride. 

 The antimonious chloride was prepared by the action of dry chlorine 

 on pure antimony, — " de I'antimoine tres-pur et du chlor sec," — and 

 purified by repeated distillations over the metal in fine powder. A 

 weighed amount of this chloride was added to a solution of tartaric 

 acid in water, and the chlorine directly precij^itated in the usual way. 

 Dumas adds: "Je n'ai entrevu ni apparence de cause d'erreur particu- 

 liere, ni irregularite dans les resultats." He gives four determina- 

 tions as follows : — 



1. 1.876 of SbClg correspond to 2.660 Ag; hence Sb = 122.00 



2. 4.336 „ „ 6.148 „ „ =122.00 



3. 5.065 „ „ 7.175 „ „ =122.20 



4. 3.475 „ „ 4.930 „ „ =121.94 



The first three were from the same, but the last from a different 

 preparation. From these results, Dumas deduces as the most probable 

 value of the atomic weight of antimony the whole number 122, and 

 this differs from the extreme value obtained by only 0.2. It will be 

 noticed that the method of Dumas is essentially the same as that of 

 Rose, only the former did not separate the antimony from the solution 

 before precipitating with argentic nitrate. This, however, may be an 

 important difference ; for, as we shall show hereafter, an excess of 

 argentic nitrate, added to a solution containing antimonious chloride 

 and tartaric acid, above the amount necessary to precipitate the chlo- 

 rine, determines the formation of argento-antimonious tartrate, which 

 slowly crystallizes out from the solution on standing, and is almost 

 wholly insoluble in cold water. The occlusion of this material bv 

 the precipitated argentic chloride on the one hand, and on the other 

 hand the slight solubility which we also noticed of this precipitate 

 in the resulting menstruum, gave us a very different impression of 

 the accuracy of the process from that obtained by Dumas. Rose, 

 however, does not mention these possible sources of error. It seems 

 probable that Weber, under his direction, aimed to estimate tlie anti- 

 mony as well as the chlorine of the compound analyzed, and for this 

 reason precipitated the antimony first. Moreover, the chief of the 

 causes of error we have noticed would tend to lower the observed 

 atomic weight of antimony ; and our experience would lead us to ques- 

 tion whether the previous precipitation of the antimony would not 

 occasion more error than it prevents. 



The only other determination of the atomic weight of antimony 



