eighty-four. He worked on the problem of the constitution of indigo for
fifteen years and discovered several ways of making it. It is possible
to start from benzene, toluene or naphthalene. The first process was the
easiest, but if you will refer to the products of the distillation of
tar you will find that the amount of toluene produced is less than the
naphthalene, which is hard to dispose of. That is, if a dye factory had
worked out a process for making indigo from toluene it would not be
practicable because there was not enough toluene produced to supply the
demand for indigo. So the more complicated napthalene process was
chosen in preference to the others in order to utilize this by-product.

The Badische Anilin-und-Soda Fabrik spent $5,000,000 and seventeen years
in chemical research before they could make indigo, but they gained a
monopoly (or, to be exact, ninety-six per cent.) of the world's
production. A hundred years ago indigo cost as much as $4 a pound. In
1914 we were paying fifteen cents a pound for it. Even the pauper labor
of India could not compete with the German chemists at that price. At
the beginning of the present century Germany was paying more than
$3,000,000 a year for indigo. Fourteen years later Germany was _selling_
indigo to the amount of $12,600,000. Besides its cheapness, artificial
indigo is preferable because it is of uniform quality and greater
purity. Vegetable indigo contains from forty to eighty per cent. of
impurities, among them various other tinctorial substances. Artificial
indigo is made pure and of any desired strength, so the dyers can depend
on it.

The value of the aniline colors lies in their infinite variety. Some are
fast, some will fade, some will stand wear and weather as long as the
fabric, some will wash out on the spot. Dyes can be made that will
attach themselves to wool, to silk or to cotton, and give it any shade