94 ATOMIC WEIGHT DETERMINATIONS. 



ings are reduced to vacuum. CI = 35.457 ; Ag = 107.93. 

 {Stas, Unters. uber Cheni. Prop. Leipzig, 1867.) 



OSMIUM. 



Regnault has determined the specific heat of osmium. It 

 corresponds to an atomic weight of about 199. [G-melin- 

 Kraut, I. c.) 



J. J. Berzelius : 199.04, (O = 16). 



Berzelius analyzed potassium chloro-osmate by reduction 

 in a current of hydrogen and solution of the potassium 

 chloride from the residue. 1.3165 grammes of the double 

 salt lost 0.3805 in reduction and the residue was composed 

 of 0.401 potassium chloride and 0.535 osmium. The atomic 

 weight may be calculated either from the chlorine lost or 

 from the relation of the chloride to the metal in the residue. 

 Berzelius preferred the latter as more probably accurate. 

 [If K = 39.137; 01 = 35.457 (Stas;) this relation gives 

 199.04.] According to W. M. Watts, (Ohem. News, 19, 

 302) the loss of chlorine gives for Stas's values Os =: 199.42. 

 Hyperosraic acid was separated from iridium compounds by 

 distilling at a gentle heat. The first portion is perfectly 

 pure. The metal was precipitated from chlorhydric acid 

 solution of hyperosmic acid by mercury and subsequently 

 purified by heating in a current of hydrogen. Potassium 

 chloro-osmate was formed by heating comminuted metal 

 and KCl in a current of chlorine. {Foggend. Ann., 13, 1828, 

 530 ; Kongl. Vet. Acad. HandL, 1828.) 



E. Fremy : 199.65 (0 = 16) ; 1247.8 (0 = 100). 



Pure osmium was burned in a current of oxygen and 

 the fumes led over potassic hydrate, by which they are 

 absorbed. An additional potash tube did not increase in 

 weight. Oorks were avoided. Number of experiments not 

 given. {Erdmann's Journ. fiir Prak. Chem., 83, 1844, 409 ; 

 Journ. de Pharm. et Chim., 1844, 241.) 



Deville and Debray : 198 (O = 16). 



These chemists determined the vapor density of hyper- 

 osmic acid by Dumas' method, finding it 8.89 at 246°, 



