The element fluorine has at last been successfully isolated, and its chief chemical and physical properties determined. Many chemists, notably Faraday, Gore, Pflaunder, and Brauner, have endeavored to prepare this element in the free state, but all attempts have hitherto proved futile. M. Moissau, after a long series of researches with the fluorides of phosphorus, and the highly poisonous arsenic trifluoride, has finally been able to liberate fluorine in the gaseous state from anhydrous hydrofluoric acid by electrolysis. This acid in the pure state is not an electrolyte, but when potassium fluoride is dissolved in it, a current from ninety Bunsen elements decomposes it, evolving hydrogen from the negative and fluoride from the positive electrode.
The apparatus employed in this process is constructed of platinum, and is made in the form of a U tube, as shown in the accompanying illustration, with fluorspar stoppers, through which the battery terminals, made of platinum iridium alloy, are led. The gas is liberated at about the rate of two liters per hour, and has very powerful chemical properties. It smells somewhat like hypochlorous acid, etches dry glass, and decomposes water, liberating ozone, and forming hydrofluoric acid. The non-metallic elements, with the exception of chlorine, oxygen, nitrogen, and carbon, combine directly with it, evolving in most cases both light and heat. It combines with hydrogen, even in the dark, without the addition of any external energy, and converts most metals into their fluorides. Gold and platinum are not attacked in the cold, but when gently heated are easily corroded. Mercury readily dissolves the gas, forming the protochloride; iron wire also completely absorbs the gas, while powdered antimony and lead take fire in it. It is necessary in the electrolysis of the liquid hydrofluoric acid to cool the electrolytic cell by means of methyl chloride to -50° C. Fluorine appears to thus fully confirm the predictions which have been made by chemists concerning its properties.
It is by far the, most energetic of all the known elements, and its position in the halogen series is established by its property of not liberating iodine from the iodides of potassium, mercury, and lead, and also of setting free chlorine from potassium chloride. With iodine it appears to form a fluoride. No compound with oxygen has yet been obtained. - Industries.