Sugar, as a pharmaceutical agent, is employed for accelerating the
pulverization of various resinous substances, and when exhibited with
the most acrid of them, it prevents their adhesion to the coats of the
intestines, by which they might irritate and inflame them; it is also
extensively used on account of its power in preserving animal[626] and
vegetable substances. (See _Conservæ_.) Milk boiled with fine sugar will
keep for a great length of time, and might be very conveniently employed
during a long voyage. Dr. Darwin also observes that fresh meat cut into
thin slices, either raw or boiled, might be preserved in coarse sugar or
treacle, and would furnish a very salutary and nourishing diet to our
sailors. Sugar exerts also some chemical affinities which are highly
interesting to the pharmaceutic chemist. Vogel has published a paper to
shew, that when sugar is boiled with various metallic oxides, and with
different metalline salts, it has the property of decomposing them;
sometimes reducing the oxide to the state of a metal, and at others
depriving the oxide only of one of the proportionals of oxygen; thus
_sulphate of copper_ and _nitrate of mercury_ are precipitated in a
metallic form, whilst _peroxide of mercury_ and _acetate of copper_ are
converted into protoxides; _corrosive_ sublimate is changed into
_calomel_, but _calomel_ is not susceptible of any further
decomposition. All those metallic salts which have the power of
decomposing water are not affected by sugar, as those of _iron_, _zinc_,
_tin_, and _manganese_. It appears, moreover, that sugar has the
property of rendering some of the Earths soluble in water. Sugar in
water, at the temperature of 50°, is capable of dissolving one half of
its weight of lime; the solution thus produced is of a beautiful
white-wine colour, and has the smell of fresh-slacked quick-lime. It is
precipitated from the solution by the _carbonic_, _citric_, _tartaric_,
_sulphuric_, and _oxalic_ acids; and it is decomposed, by double
affinity, by _caustic_ and _carbonated potass_ and _soda_, and by the
_citrate_, _tartrate_, and _oxalate of potass_, &c. The union of sugar
with the alkalies has been long known, and in the decomposition of the
solution of lime in sugar by the salts above mentioned, the acid unites
with the lime, and the alkaline base forms a compound with the sugar.