Dr. Macbride, whose experimental researches have very justly acquired
him a high degree of reputation in the philosophical world, supposes
fixed air to be the combining principle of bodies, and has applied
this ingenious theory to pharmaceutical improvements. He discovered
that lime triturated with resinous gums, promotes their dissolution
in water; which, he thinks, is thus enabled to take up the same parts
of these substances, as are soluble in spirit of wine. These aqueous
tinctures are transparent, not milky like the solutions made with yolk
of egg, or gum arabic; but the lime communicates a highly disagreeable
taste to them, and the action of lime water, which he used in some
instances, is not sufficiently powerful to extract strong tinctures
from these bodies. As calcined Magnesia has a great affinity with fixed
air, I was desirous of trying whether it would contribute to render
resinous substances soluble in water; for being itself insoluble, the
solutions would consequently be free from any other impregnation than
that of the resins.