Chemistry and Physics. 423 



believed in an electrochemical theory of combination; and hence 

 considered it desirable to ascertain whether molecules capable of 

 combining are at different potentials and whether this difference 

 of potential increases as they are brought nearer to the point of 

 union. Moreover, whether also the conditions which affect chemi- 

 cal change affect in the same direction the passage of electric dis- 

 charge. A mixture of dry hydrogen chloride and dry ammonia in 

 equal volumes was introduced into a glass tube about a meter long, 

 divided in the middle by a threeway tap, and provided at the 

 ends with electrodes of platinum plate. On opening the tap and 

 connecting the electrodes with the terminals of a Wimshurst 

 machine giving 3 inch sparks in air, for three hours, it was found 

 that a separation of the gases had taken place; the gas surround- 

 ing the anode reddening litmus and that about the kathode blueing 

 it. Air, dried over sulphuric acid, showed after electrification 

 1*8 per cent more oxygen at the anode end of the tube; and a 

 mixture of dried hydrogen and oxygen showed 2-3 per cent excess 

 of oxygen at this end. Since then mixed gases can be partially 

 separated by the attraction of their molecules for oppositely 

 charged plates, it seems probable that the molecules themselves 

 are charged. Moreover experiment showed that the electric dis- 

 charge takes place more readily in moist than in dry air ; and 

 further that the electric glow obtained by shaking mercury in 

 different rarefied gases gradually diminishes as the gas is dried by 

 phosphorus pentoxide and finally disappears altogether. Hence 

 the author concludes that with regard to the presence of moisture, 

 electric discharge is affected in the same way as chemical com- 

 bination. If it can be regarded as proved that substances which 

 are capable of chemically combining are electrically charged, the 

 great significance of this result is obvious. — J. Ghem. ISoc, lxv, 

 611-624, July 1894. G. F. B. 



4. On the Production of free Fluorine by Chemical means. — 

 The isolation of fluorine by Moissan it will be remembered, was 

 effected by means of electrolysis. Brattnek has now succeeded 

 in obtaining this gas by a method purely chemical. He had 

 observed twelve years ago, that the compounds CeF 4 H 2 and 

 (KF) 3 (CeF 4 ) 2 (H 2 0) 2 when heated, first evolve water and then a 

 gas having the odor of hypochlorous acid and possessing the 

 property of setting iodine free from potassium iodide. He now 

 describes a new series of analogous salts, the fluorplumbates, 

 derivations of fluorplumbic acid; the first member of the series 

 having the composition (KF) 3 . HF. PbF 4 , and being produced in 

 one of three ways: (1) by treating the oxide Pb B 7 . (H 2 0) 3 

 freshly precipitated, with a mixture of hydrogen-potassium fluor- 

 ide and hydrogen fluoride and crystallizing from hydrogen fluor- 

 ide ; (2) by fusing lead dioxide with potassium hydroxide in the 

 proportion (KOH) 3 : Pb0 2 in a silver crucible, dissolving the 

 moistened mass in excess of hydrogen fluoride and crystallizing ; 

 and (3) by dissolving three gram-molecules of KF . HF in excess of 

 hydrogen fluoride and adding one gram-molecule of lead tetrace- 



