ATOMIC WEIGHTS 



479 



II. By electrohjsis. 



2KCI. 

 3792 

 7898 

 3355 

 4167 

 5298 

 6147 

 6356 

 3908 

 5927 

 7355 

 8364 



Per cent. Pt. 

 40.092 

 40.063 

 40.126 

 40.103 

 40.104 

 40.081 

 40.117 

 40.112 

 40.065 

 40.080 

 40.108 



Per cent. KCl. 

 30.695 

 30.667 

 30.668 

 30.730 

 30.545 

 30.652 

 30.755 

 30.629 

 30.589 

 30.681 

 30.691 



Mean of nineteen experiments, 40.098, ±.0031 30. 663, ±.0080 

 Seubert found, 30.682, ±.0090 



General mean, 



30.671, ±.0060 



Hence Pt= 194.78 and 195.36, from Halberstarlt's data alone. 



The work of Dittmar and M' Arthur ' on the atomic weight of platinum 

 is difficult to discuss and essentially unsatisfactory. They investigated 

 potassium platinchloride, and came to the conclusion that it contains 

 traces of hydroxyl replacing chlorine and also hydrogen replacing potas- 

 sium. It is also liable, they think, to carry small quantities of potassium 

 chloride. In their determinations, which involve corrections indicated 

 by the foregoing considerations, they are not sufficiently explicit, and 

 give none of their actual weighings. They attempt, however, to fix the 

 ratio 2IvCl : Pt, and after a number of discordant, generally high results, 

 they give the following data for the atomic weight of platinum based 

 upon the assumption that 2KC1 = 149.182 : 



195.54 

 195.48 

 195.60 

 195.37 



Mean, 195.50, ± .0330 



This ratio can also be computed from Seubert's and Halberstadt's analy- 

 ses, and also the ratio 2KBr : Pt. It has not seemed necessary to do so, 

 in view of the overwhelming weight of Archibald's more recent \\ork. 



Dittmar and M'Arthur also discuss Seubert's determinations, seeking 

 to show that the latter also, properly treated, lead to a value nearer to 

 195.5 than to 195. Seubert at once replied to them," pointing out that 



1 Trans. Roy. Soc. Edinburgh, 33, 561. 1887. 

 2Ber. Deutsch. chem. Gesell., 21, 2179. 1888. 



