clear
glass, milk-white when cold; the sulphate is very difficultly fusible.
Both strongly heated at the point of the blue flame impart a green
tinge to the outer flame. When combined with silica it cannot be well
discovered by the blowpipe. In solution, salts of baryta yield, with
sulphuric acid or solution of sulphate of lime, immediately a fine white precipitate insoluble in acids or alkalies.
Strontia, the
carbonate, even in thin plates, only melts on the edges, and forms
cauliflower-like projections of dazzling brightness; the sulphate melts
easily in the oxidating flame, and in the reducing flame is changed
into sulphuret of strontium, which, dissolved in hydrochloric acid, and
evaporated to dryness, gives a fine carmine-red color to the flame of
alcohol. Strontia in solution gives a precipitate with sulphuric- acid,
or with sulphate of lime, but not immediately.
Lime.—The
carbonate is rendered caustic by heat, when it has alkaline properties,
and readily absorbs water. The sulphate in the reducing flame changes
to the sulphuret of calcium, which is also alkaline. Sulphuric acid
precipitates lime only from very concentrated solutions; oxalic acid
even from very weak ones; and silico-hydrofluoric acid not at all. As
baryta and strontia also form precipitates with the first two reagents,
they must previously be separated by sulphate of potassa. Chloride of
calcium tinges the flame of alcohol yellowish-red.
Magnesia, alone,
or as a hydrate, a carbonate, and in • some other combinations, when
ignited with solution of cobalt, or the oxalate of cobalt, assumes a
light-red tint. It is not precipitated from a solution either by
sulphuric acid, oxalic acid, or silico-hydrofluoric acid; but
phosphoric acid, with ammonia, throws down a white crystalline
precipitate of phosphate of ammonia and magnesia.
Alumina alone is infusible. In many combinations, when
