_Boric anhydride_ is raised to a most vivid incandescence by fluorine, the experiment being rendered very beautiful by the abundant white fumes of the trifluoride which are liberated. _Silicon dioxide_, one of the most inert of substances at the ordinary temperature, takes fire in the cold in contact with fluorine, becoming instantly white-hot, and rapidly disappearing in the form of silicon tetrafluoride. The _chlorides_ of both _boron_ and _silicon_ are decomposed by fluorine, with formation of fluorides and liberation of chlorine, the reaction being accompanied by the production of flame. ACTION OF FLUORINE UPON METALLIC COMPOUNDS. _Chlorides_ of the metals are instantly decomposed by fluorine, generally at the ordinary temperature, and in certain cases, antimony trichloride for instance, with the appearance of flame. Chlorine is in each case liberated, and a fluoride of the metal formed. A few require heating, when a similar decomposition occurs, often accompanied by incandescence, as in case of chromium sesquichloride. _Bromides_ and _iodides_ are decomposed with even greater energy, and the liberated bromine and iodine burn in the fluorine with formation of their respective fluorides. _Cyanides_ react in a most beautiful manner with fluorine, the displaced cyanogen burning with a purple flame. Potassium ferrocyanide in particular affords a very pretty experiment, and reacts in the cold. Ordinary potassium cyanide requires slightly warming in order to start the combustion. Fused _potash_ yields potassium fluoride and ozone. Aqueous potash does not form potassium hypofluorite when fluorine is bubbled into it, but only potassium fluoride. _Lime_ becomes most brilliantly incandescent, owing partly to the excess being raised to a very high temperature by the heat developed during the decomposition, and partly to the phosphorescence of the calcium fluoride formed. _Sulphides_ of the alkalies and alkaline earths are also immediately rendered incandescent, fluorides of the metal and sulphur being respectively formed. _Boron nitride_ behaves in an exceedingly beautiful manner, being attacked in the cold, and emitting a brilliant blue light which is surrounded by a halo of the fumes of boron fluoride. _Sulphates_, _nitrates_ and _phosphates_ generally require the application of more or less heat, when they too are rapidly and energetically decomposed. Calcium phosphate is attacked in the cold like lime, giving out a brilliant white light, and producing calcium fluoride and gaseous oxyfluoride of phosphorus, POF_{3}. _Calcium carbonate_ also becomes raised to brilliant incandescence when exposed to fluorine gas, as does also normal _sodium carbonate_; but curiously enough the bicarbonates of the alkalies do not react with fluorine even at red heat. Perhaps this may be explained by the fact that fluorine has no action at available temperatures upon carbon dioxide. ACTION OF FLUORINE UPON A FEW ORGANIC COMPOUNDS.