220 THE ATOMIC WEIGHTS. 



Per cent. O. 



1.8576 grm. SbCl 3 needed .5967 grm. K 2 Cr 2 O 7 and 33.4 cc. sol. 7.0338 

 1.9118 " .3019 " KC1O 3 " 16.2 " 7.0321 



4.1235 " .6801 " KC1O 3 " 23.2 " 7.0222 



Mean, 7.0294, .0024 



The fourth set of experiments was gravimetric. The solution of Sb01 3 

 mixed with tartaric acid, was first precipitated by hydrogen sulphide, 

 in order to remove the antimony. The excess of H 2 S was corrected by 

 copper sulphate, and then the chlorine was estimated as silver chloride 

 in the ordinary manner. 100 parts of AgCl correspond to the amounts 

 of SbCl 3 given in the third column. 



1.8662 grm. SbCl 3 gave 3.483 grm. AgCl. 53-58o 



1.6832 3.141 " 53.588 



27437 5-IH5 " 53-677 



2.6798 5.0025 " 53.569 



5.047 9.411 53.629 



3.8975 " 7.2585 " 53.696 



Mean, 53.623, =b .015 



The volumetric series with'SbC! 3 gave Kessler values for Sb ranging 

 from 121.16 to 121.47. The gravimetric series, on the other hand, yielded 

 results from Sb = 124.12 to 124.67. This discrepancy Kessler rightly 

 attributes to the presence of oxygen in the chloride; and, ingeniously 

 correcting for this error, he deduces from both sets combined the value of 

 Sb = 122.37. 



The several mean results for antimony agree so fairly w r ith each other, 

 and with the estimates obtained by Dexter and Dumas, that we cannot 

 wonder that Kessler felt satisfied of their general correctness, and of the 

 inaccuracy of the figures published by Schneider. Still, the old series 

 of data obtained by the titration of tartar emetic with dichromate con- 

 tained no evident errors, and was not accounted for. This series,* if 

 we reduce all of Kessler's figures to a single common standard, gives a 

 ratio between K 2 Cr 2 7 and C 4 H 4 KSb0 7 .H 2 0. 100 parts of the former 

 will oxidize of the latter : 



336.64 



338.01 



336.83 



337-93 



338.59 



335 ; 79 



Mean, 337.30, .29 



From this, if K,Cr 2 7 = 292.271, Sb = 118.024. 



The newer atomic weights found in other chapters of this work will 



*Poggend. Annalen, 95, 217. 



