A gas plant was started at Edgewood,
Maryland, in November, 1917. By March it was filling shell and before
the war put a stop to its activities in the fall it was producing
1,300,000 pounds of chlorine, 1,000,000 pounds of chlorpicrin, 1,300,000
pounds of phosgene and 700,000 pounds of mustard gas a month.
Chlorine, the first gas used, is unpleasantly familiar to every one who
has entered a chemical laboratory or who has smelled the breath of
bleaching powder. It is a greenish-yellow gas made from common salt. The
Germans employed it at Ypres by laying cylinders of the liquefied gas in
the trenches, about a yard apart, and running a lead discharge pipe over
the parapet. When the stop cocks are turned the gas streams out and
since it is two and a half times as heavy as air it rolls over the
ground like a noisome mist. It works best when the ground slopes gently
down toward the enemy and when the wind blows in that direction at a
rate between four and twelve miles an hour. But the wind, being strictly
neutral, may change its direction without warning and then the gases
turn back in their flight and attack their own side, something that
rifle bullets have never been known to do.
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