ATOMIC WEIGHTS 321 



saturated solution in bisulphide of carbon. The portions analyzed 

 were dissolved in concentrated aqueous tartaric acid, and precipitated 

 by silver nitrate, many precautions being observed. The silver chloride 

 was collected by reverse filtration, and dried at temperatures from 110° 

 to 120°. In one experiment the antimony was first removed by 11,8. 

 Seventeen experiments were made as follows. If we reduce to a common 

 standard, Cooke's analyses give, as proportional to 100 parts of AgCl, 

 the quantities of SbClg stated in the third column : 



1.5974 grm. SbClg gave 3.0124 grm. AgCl. 53.028 



1.2533 " 2.3620 " 53.061 



.8876 " 1.6754 " 52.978 



.8336 " 1.5674 " 53.184 



.5326 " 1.0021 " 53.148 



.7270 " 1.3691 " 53.101 



1.2679 " 2.3883 " 53.088 



1.9422 " 3.6646 " 52.999 



1.7702 " 3.3384 " 53.025 



2.5030 " 4.7184 " 53.048 



2.1450 " 4.0410 " 53.081 



1.7697 " 3.3281 " 53.175 



2.3435 " 4.4157 " 53.072 



1.3686 " 2.5813 " 53.020 



1.8638 " 3.5146 " 53.030 



2.0300 " 3.8282 " 53.028 



2.4450 " 4.6086 " 53.053 



Mean, 53.066, ± .0096 

 Hence Sb = 121.82. 

 This mean may be combined with that of Kessler's series, as follows : 



Kessler 53.623, ± .015 



Cooke 53.066, ± .0096 



General mean 53.2311, ± .008 



The results thus obtained with SbCls confirmed Dumas' determination 

 of the atomic weight of antimony as remarkably as the syntheses of SbjSg 

 had sustained the work of Schneider. Evidently, in one or the other 

 series a constant error must be hidden, and much time was spent by 

 Cooke in searching for it. It was eventually found that the chloride of 

 antimony invariably contained traces of oxychloride, an impurity which 

 tended to increase the apparent atomic weight of the metal under con- 

 sideration. It was also found, in the course of the investigation, that 

 hydrochloric acid solutions of antimonious compounds oxidize in the air 

 during boiling as rapidly as ferrous compounds, a fact which explains 

 the high values for antimony found by Kessler.^ 



1 In Amer. Journ. Sei. (3), 21, 220, Ciooke pointed out the errors due to the solubility of silver 

 chloride, and gave two series of analyses of SbCl^ to illustrate their magnitude. 



