CHEMISTRY. 399 



tliird, which finally removed all doubts as to the nature of the gas 

 separated in the experiments. 



Moissan prepared anhydrous hydrofluoric acid after the method of 

 Fremy, taking great precautious to eliminate water. This acid was 

 placed in a phitinum (J-tube, cooled to —50° 0. and submitted to the 

 action of an electric current from fifty Bunsen cells. Under these con- 

 ditions hydrogen was set free at the negative pole, and at the positive 

 pole a gas was obtained in a continuous current and having the follow- 

 ing properties: In the presence of mercury it is completely absorbed, 

 with formation of mercury fluoride of a light yellow color ; the gas 

 decomposes water, liberating ozone: phosphorus is ignited by it ; sul- 

 phur is heated, melting rapidly; carbon seems to be without action; 

 melted potassium chloride is attacked with an escape of chlorine ; crys- 

 talline silicou, purified by treatment with nitric and hydrofluoric acids, 

 takes fire iu contact with this gas and burns brilliantly, forming silicon 

 flu(»ride. The electrode of platiniridium forming the positive pole is 

 strongly corroded, while that of the negative pole is untouched. 



Moissan pointed out that the simplest explanation of these reactions 

 is that they are due to elementary fluorine, but he deferred decision 

 until he could show that the phenomena were not due to hydrogen per- 

 fluoride or to a mixture of ozone and hydrofluoric acid. 



In the second memoir Moissan details the precautions observed in pre- 

 paring the anhydrous hydrofluoric acid and gives additional data con- 

 cerning the behavior of the gas. The anhydrous acid is made by heating 

 to redness in a platinum vessel very carefully dried double fluoride of 

 potassium and hydrogen (HF KF), the liquid being condensed in a re- 

 ceiver cooled with a mixture of ice and salt. The anhydrous acid boils 

 at 11P.5, is very hygroscopic, and fumes abundantly in moist air. For 

 electrolysis the acid was cooled with chloride of methyl to —23^', and a 

 current of twenty Bunsen cells sufficed. Absolutely anhydrous hydro- 

 fluoric acid will not conduct electricity, therefore a small quantity of 

 fused double fluoride of potassium ,and hydrogen is added. 



The gas liberated at the positiv^pole not only attacks silicon in the 

 cold, but adamantine boron as well. 



Sulphur takes fire iu the gas, as do arsenic and antimony. The 

 metals are attacked with less energy ; organic bodies, however, are vio- 

 lently attacked; alcohol, ether, benzene, petroleum, etc., take fire on 

 contact. 



When the experiment has lasted several hours and the gases are no 

 longer separated by liquid hydrofluoric acid in the bend of the tube, 

 the gases H and F recombine in the cold with violent detonation. 



In the third memoir the author shows that the same gas can be ob- 

 tained by the electrolysis of carefully dried and fused double fluoride 

 of hydrogen and potassium. The temperature maintained is 110°. 

 He also describes experiments showing conclusively that the gas in 

 question is free fluorine; under certain conditions the gas was absorbed 



