CHEMICAL SCIENCE. 241 



Fluoride of mercury does not exist in the anhydrous state ; and when 

 hydrated, it produces, by the action of heat, oxygen and acid vapors. 



We must therefore abandon the attempt to obtain fluorine from these 

 fluorides. I was then led by a series of experiments, which it is impossi-" 

 ble to describe in this abstract, but which are all given in the memoir, to 

 subject the anhydrous fluorides to powerful decomposing agents. 



Guided by some experiments which I am at this time making with M. 

 Ed. Becquerel, in which chloride of calcium, in fusion, is very rapidly de- 

 composed by the battery, I first subjected the fused anhydrous fluorides, 

 such as those of potassium, lead, and calcium, to an electric current. The 

 decomposition was easily effected ; I saw a gas disengaged at the positive 

 pole, which powerfully attacked platinum. But the many difficulties sur- 

 rounding this experiment have hitherto prevented me from collecting the 

 gas thus disengaged, so as to be able to study it properly. 



Sulphur acts under the influence of heat on a certain number of anhy- 

 drous fluorides, replacing the fluorine ; but combinations of fluorine and 

 sulphur are then formed, which will be studied in another work. 



The action of chlorine on the anhydrous fluorides, especially on fluoride 

 of calcium, gave me important results. All my experiments were made 

 in platinum tubes, which were not attacked at a red heat by chlorine. The 

 gas was dried with the greatest care by several tubes of anhydrous phos- 

 phoric acid, so as to avoid the rapid action of steam on the fluorides. I 

 found that at a white heat dry chlorine very slowly decomposes fluoride 

 of calcium, and disengages a gas which powerfully attacks glass, and which 

 appeared to be fluorine. Oxygen, passing at a white heat over fluoride of 

 calcium, decomposes it more quickly than chlorine, and produces, as in 

 the preceding experiment, a gas which attacks glass. 



Such is a summary of my experiments on the fluorides ; but I shall not 

 consider my task complete until I have really isolated a body of which. I 

 have hitherto merely caught a glimpse. 



EXPERIMENTS ON COPPER AND COPPER SHEATHING. 



For the purpose of experiment, M. Bobierre has made with metals, either 

 pure or impure, ingots of bronze of a cylindrical form by castings in sand, 

 having a height of forty centimeters and weighing twenty-five kilo- 

 grammes. Portions for analysis were taken from different parts of the 

 ingots, both from the surface and interior. The central parts in all cases 

 contained less tin than the surface. For example, in the alloy of ninety- 

 seven copper and three of tin, the richness in tin for the tin parts had the 

 ratio of 1 to 3.97. On adding to the alloy one per cent, of zinc, the homo- 

 geneity was much increased, the ratio becoming 1 to 1.4-5. 



Under Louis XIV., the cannon were of a better quality than those of 

 the present time ; zinc was mixed with the metal in the condition of brass. 

 The trials made in our time have failed, because the zinc was introduced 

 11 



