d, by the process known as
the quick vinegar manufacture, depends upon principles, at a
knowledge of which we have arrived by a careful study of these
properties.

LETTER III

My dear Sir,

The manufacture of soda from common culinary salt, may be regarded
as the foundation of all our modern improvements in the domestic
arts; and we may take it as affording an excellent illustration of
the dependence of the various branches of human industry and
commerce upon each other, and their relation to chemistry.

Soda has been used from time immemorial in the manufacture of soap
and glass, two chemical productions which employ and keep in
circulation an immense amount of capital. The quantity of soap
consumed by a nation would be no inaccurate measure whereby to
estimate its wealth and civilisation. Of two countries, with an
equal amount of population, the wealthiest and most highly civilised
will consume the greatest weight of soap. This consumption does not
subserve sensual gratification, nor depend upon fashion, but upon
the feeling of the beauty, comfort, and welfare, attendant upon
cleanliness; and a regard to this feeling is coincident with wealth
and civilisation. The rich in the middle ages concealed a want of
cleanliness in their clothes and persons under a profusion of costly
scents and essences, whilst they were more luxurious in eating and
drinking, in apparel and horses. With us a want of cleanliness is
equivalent to insupportable misery and misfortune.

Soap belongs to those manufactured products, the money value of
which continually disappears from circulation, and requires to be
continually renewed. It is one of the few substances which are
entirely consumed by use, leaving no product of any worth. Broken
glass and bottles are by no means absolutely worthless; for rags we
may purchase new cloth, but soap-water has no value whatever. It
would be interesting to know accurately the amount of capital
involved in the manufacture of soap; it is certainly as large as
that employed in the coffee trade, with this important difference as
respects Germany, that it is entirely derived from our own soil.

France formerly imported soda from Spain,--Spanish sodas being of
the best quality--at an annual expenditure of twenty to thirty
millions of francs. During the war with England the price of soda,
and consequently of soap and glass, rose continually; and all
manufactures suffered in consequence.

The presen