98 ATOMIC WEIGHT DETERMINATIONS. 



PLATINUM. 



Regnault and Kopp have determined the specific heat of 

 platinum. It answers to an atomic weight of about 197. 



{Grnelin-Kraut, I. c.) 



J. J. Berzelius : 197.19 (0 = 16). 



Determined by the same method as osmium, q. v., from 

 a single experiment on potassium auroplatinate. 2.135 

 potassium chloride accompanied 2.822 platinum. [If KCI 

 = 74.594 (Stas,) this gives the above value.] The salt was 

 prepared by precipitating an alcoholic solution of platinum 

 chloride with potassium chloride, washing with alcohol and 

 heating to redness in a current of chlorine. Berzelius re- 

 marks that the metal used in his former determinations 

 was impure. [Poggend. Ann., 13, 1828, 468, and Lehrbuch, 

 3, 1213.) 



T. Andrews : 197.88 (0 = 16). 



Determined by three experiments on potassium chlo- 

 roplatinate. The salt was dried at 105° in vacuo, decom- 

 posed by zinc, the excess of zinc removed by acetic acid, 

 the solution filtered ofiF, and the chlorine titrated. The 

 number is the mean ; extreme difference, 0.22. The values 

 assumed for Ag and CI are not given. They were most 

 likely Mariguac's. {Brit. Assoc. Rep., 1852, part 2, 33.) 



J. S. Stas made preparations for determining the atomic 

 weight of platinum, but not being able to produce potas- 

 sium chloroplatinate entirely free from water, and being 

 unacquainted with Bunsen's method of accomplishing this 

 end, resigned the attempt. He made, indeed, three analy- 

 ses by the same method employed by Berzelius, but un- 

 fortunately does not communicate the results. {Stas, Unter- 

 such. iiber Chem. Prop., Leipzig, 1867, 265.) 



POTASSIUM. 



Regnault determined the specific heat of potassium. It 

 corresponds to an atomic weight of about 39. {Gmelin- 

 Kraut, l. c.) 



