If strontia or its compounds are fused with a green bead of carbonate of soda and sesquioxide of manganese, as described under the head of baryta, a bead of a brown, brownish-green, or dark grey color is produced.  Carbonate of soda does not dissolve pure strontia.  The carbonate and sulphate of strontia melt with soda upon platinum foil to a bead, which is milk-white when cold, but fused upon charcoal they are absorbed.  Strontia or its compounds produce with borax, or microcosmic salt, the same reactions as baryta.  When they are moistened with nitrate of cobalt, and ignited in the oxidizing flame, a black, or grey infusible mass is produced.

(c.) Lime, Oxide of Calcium (CaO).—­Lime does not occur free in nature, but in combination with acids, chiefly the carbonic and sulphuric.  The phosphate occurs principally in bones.  The hydrate and the salts of lime are in their properties similar to those of the two preceding alkaline earths.  In the pure state, the oxide of calcium is white; it slakes, produces a high temperature, and falls into a white powder when sprinkled with a little water.  It is now a hydrate, and has greatly increased in volume.  The hydrate of lime is far less soluble in water than either those of baryta or strontia, and is less soluble in hot water than in cold.  Lime, its hydrate and sulphide of calcium, have a strong alkaline reaction upon red litmus paper.  Lime and its hydrate are infusible, but produce at a strong red heat a very intense and splendid white light, while the hydrate loses its water.  The carbonate of lime is also infusible, but at a red heat the carbonic acid is expelled, and the residue becomes caustic, appears whiter, and produces an intenser light.  The sulphate of lime melts with difficulty, and presents the appearance of an enamelled mass when cold.  By heating it upon charcoal it fuses in the reducing flame, and is reduced to a sulphide.  This has a strong hepatic odor, and exerts an alkaline reaction upon red litmus paper.  By exposing lime, or its compounds, upon platinum wire—­or as a small splinter of the mineral in the platinum tongs—­to the point of the blue flame, a purple color, similar to that of lithia and strontia, is communicated to the external flame, but this color is not so intense as that produced by strontia, and appears mixed with a slight tinge of yellow.  This color is most intense with the chloride of calcium, while the carbonate of lime produces at first a yellowish color, which becomes red, after the expulsion of the carbonic acid.  Sulphate of lime produces the same color, but not so intense.  Among the silicates of lime only the tablespar (3CaO, 2SiO^{3}) produces a red color.  Fluorspar (CaFl) produces a red as intense as pure lime, and fuses into a bead.  Phosphate and borate of lime produce a green flame which is only characteristic of their acids.  The presence of baryta communicates a green color to the flame.  The presence of soda produces only a yellow color in the external flame.