If alcohol is poured over lime or its compounds and inflamed, a red color is communicated to the flame.  The presence of baryta or soda prevents this reaction.  Lime and its compounds do not dissolve much by fusion with carbonate of soda.  If this fusion is effected on charcoal, the carbonate of soda is absorbed and the lime remains as a half-globular infusible mass on the charcoal.  This is what distinguishes lime from baryta and strontia, and is a good method of separating the former from the latter.  Lime and its compounds fuse with borax in the oxidizing and reducing flames to a clear bead, which remains clear when cold, but when overcharged with an excess or heated intermittingly, the bead appears, when cold, crystalline and uneven, and is not so milk-white as the bead of baryta or strontia, produced under the same circumstances.  The carbonate of lime is dissolved with a peculiar hissing noise.  Microcosmic salt dissolves a large quantity of lime into a clear bead, which is milky when cold.  When the bead has been overcharged with lime, by a less excess, or by an intermittent flame, we will perceive in the bead, when cold, fine crystals in the form of needles.  Lime and its compounds form by ignition with nitrate of cobalt, a black or greyish-black infusible mass.

(d.) Magnesia (MgO).—­Magnesia occurs in nature in several minerals.  It exists in considerable quantity combined with carbonic, sulphuric, phosphoric, and silicic acids, etc.  Magnesia and its hydrate are white and very voluminous, scarcely soluble in hot or cold water, and restores moistened red litmus paper to its original blue color.  Magnesia and its hydrate are infusible, the latter losing its water by ignition.  The carbonate of magnesia is infusible, loses its carbonic acid at a red heat, and shrinks a little.  It now exerts upon red litmus paper an alkaline reaction.  The sulphate of magnesia, at a red heat, loses its water and sulphuric acid, is entirely infusible, and gives now an alkaline reaction.  The artificial Astrachanit (NaO, SO^{3} + MgO, SO^{3} + 4HO) fuses easily.  When fused on charcoal, the greater part of the sulphate of soda is absorbed, and there remains an infusible mass.

Magnesia and its compounds do not produce any color in the external flame, when heated in the point of the blue flame.  The most of the magnesia minerals yield some water when heated in a glass tube closed at one end.

Magnesia, in the pure state, or as the hydrate, does not fuse with soda.  Some of its compounds are infusible likewise with soda, and swell up slightly, while others of them melt with soda to a slightly opaque mass.  Some few (such as the borate of magnesia) give a clear bead with soda, though it becomes slightly turbid by cooling when saturated with magnesia, and crystallizes in large facets.