PLATINUM. 333 



//. By Electrolysis. 



General mean, 40.101, ± .0026 30.671, =b .0060 



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

 is difHcult 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 

 potassium. 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 ex- 

 plicit, and give none of their actual weighings. They attempt, however, 

 to fix the ratio 2KC1 : Pt, and after a number of discordant, generally 

 high results, they give the following data for the atomic weight of plati- 

 num based upon the assumption that 2KC1 = 149.182 : 



195-54 

 195.48 

 195.60 

 195-37 



Mean, 195.50, ± .0330. 



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,t pointing out that 

 the concordance between his determinations by very different methods 

 (a concordance verified by Halberstadt's investigation) precluded the 

 existence of errors due to impurities such as Dittmar and M'Arthur 

 assumed. 



* Trans. Roy. Soc. Edinburgh, 33, 561. 1SS7. 

 tBer. Deutsch. Chem. Gesell., 21, 2179. 18S8. 



