APTER XX

MAN'S CONQUEST OF SUBSTANCES

201. Chemistry. Man's mechanical inventions have been equaled by his
chemical researches and discoveries, and by the application he has
made of his new knowledge.

The plain cotton frock of our grandmothers had its death knell sounded
a few years ago, when John Mercer showed that cotton fabrics soaked in
caustic soda assumed under certain conditions a silky sheen, and when
dyed took on beautiful and varied hues. The demonstration of this
simple fact laid the foundation for the manufacture of a vast variety
of attractive dress materials known as mercerized cotton.

Possibly no industry has been more affected by chemical discovery than
that of dyeing. Those of us who have seen the old masterpieces in
painting, or reproductions of them, know the softness, the mellowness,
the richness of tints employed by the old masters. But if we look for
the brilliancy and variety of color seen in our own day, the search
will be fruitless, because these were unknown until a half century
ago. Up to that time, dyes were few in number and were extracted
solely from plants, principally from the indigo and madder plants. But
about the year 1856 it was discovered that dyes in much greater
variety and in purer form could be obtained from coal tar. This
chemical production of dyes has now largely supplanted the original
method, and the industry has grown so rapidly that a single firm
produced in one year from coal tar a quantity of indigo dye which
under the natural process of plant extraction would have required a
quarter million acres of indigo plant.

The abundance and cheapness of newspapers, coarse wrapping papers,
etc., is due to the fact that man has learned to substitute wood for
rags in the manufacture of paper. Investigation brought out the fact
that wood contained the substance which made rags valuable for paper
making. Since the supply of rags was far less than the demand, the
problem of the extraction from wood of the paper-forming substance was
a vital one. From repeated trials, it was found that caustic soda when
heated with wood chips destroyed everything in the wood except the
desired substance, cellulose; this could be removed, bleached, dried,
and pressed into paper. The substitution of wood for rags has made
possible the daily issue of newspapers, for the making of which
sufficient material would not otherwise have been available. When we
reflect that a daily paper of wide circu