r has been the coke ovens. When coal is heated in retorts
or ovens for making coke or gas a lot of ammonia comes off with the
other products of decomposition and is caught in the sulfuric acid used
to wash the gas as ammonium sulfate. Our American coke-makers have been
in the habit of letting this escape into the air and consequently we
have been losing some 700,000 tons of ammonium salts every year, enough
to keep our land rich and give us all the explosives we should need. But
now they are reforming and putting in ovens that save the by-products
such as ammonia and coal tar, so in 1916 we got from this source 325,000
tons a year.

[Illustration: Courtesy of _Scientific American_.

Consumption of potash for agricultural purposes in different countries]

Germany had a natural monopoly of potash as Chile had a natural monopoly
of nitrates. The agriculture of Europe and America has been virtually
dependent upon these two sources of plant foods. Now when the world was
cleft in twain by the shock of August, 1914, the Allied Powers had the
nitrates and the Central Powers had the potash. If Germany had not had
up her sleeve a new process for making nitrates she could not long have
carried on a war and doubtless would not have ventured upon it. But the
outside world had no such substitute for the German potash salts and
has not yet discovered one. Consequently the price of potash in the
United States jumped from $40 to $400 and the cost of food went up with
it. Even under the stimulus of prices ten times the normal and with
chemists searching furnace crannies and bad lands the United States was
able to scrape up less than 10,000 tons of potash in 1916, and this was
barely enough to satisfy our needs for two weeks!

[Illustration: What happened to potash when the war broke out. This
diagram from the _Journal of Industrial and Engineering Chemistry_ of
July, 1917, shows how the supply of potassium muriate from Germany was
shut off in 1914 and how its price rose.]

Yet potash compounds are as cheap as dirt. Pick up a handful of gravel
and you will be able to find much of it feldspar or other mineral
containing some ten per cent. of potash. Unfortunately it is in
combination with silica, which is harder to break up than a trust.

But "constant washing wears away stones" and the potash that the
metallurgist finds too hard to extract in his hottest furnace is washed
out in the course of time through the dropping of the gentle r