For this reason
John Davy, who discovered the compound over a hundred years ago, named
it phosgene, that is, "produced by light." The same roots recur in
hydrogen, so named because it is "produced from water," and phosphorus,
because it is a "light-bearer."
In its modern manufacture the catalyzer or instigator of the combination
is not sunlight but porous carbon. This is packed in iron boxes eight
feet long, through which the mixture of the two gases was forced. Carbon
monoxide may be made by burning coke with a supply of air insufficient
for complete combustion, but in order to get the pure gas necessary for
the phosgene common air was not used, but instead pure oxygen extracted
from it by a liquid air plant.
Phosgene is a gas that may be condensed easily to a liquid by cooling it
down to 46 degrees Fahrenheit. A mixture of three-quarters chlorine with
one-quarter phosgene has been found most effective. By itself phosgene
has an inoffensive odor somewhat like green corn and so may fail to
arouse apprehension until a toxic concentration is reached.
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