As each new gas employed by the enemy
was detected it became the business of our chemists to discover some
method of absorbing or neutralizing it. Porous charcoal, best made from
such dense wood as coconut shells, was packed in the respirator box
together with layers of such chemicals as will catch the gases to be
expected. Charcoal absorbs large quantities of any gas. Soda lime and
potassium permanganate and nickel salts were among the neutralizers
used.

The mask is fitted tightly about the face or over the head with rubber.
The nostrils are kept closed with a clip so breathing must be done
through the mouth and no air can be inhaled except that passing through
the absorbent cylinder. Men within five miles of the front were required
to wear the masks slung on their chests so they could be put on within
six seconds. A well-made mask with a fresh box afforded almost complete
immunity for a time and the soldiers learned within a few days to
handle their masks adroitly. So the problem of defense against this new
offensive was solved satisfactorily, while no such adequate protection
against the older weapons of bayonet and shrapnel has yet been devised.

Then the problem of the offense was to catch the opponent with his
mask off or to make him take it off. Here the lachrymators and
the sternutators, the tear gases and the sneeze gases, came into
play. Phenylcarbylamine chloride would make the bravest soldier
weep on the battlefield with the abandonment of a Greek hero.
Di-phenyl-chloro-arsine would set him sneezing. The Germans alternated
these with diabolical ingenuity so as to catch us unawares. Some shells
gave off voluminous smoke or a vile stench without doing much harm, but
by the time our men got used to these and grew careless about their
masks a few shells of some extremely poisonous gas were mixed with them.

The ideal gas for belligerent purposes would be odorless, colorless and
invisible, toxic even when diluted by a million parts of air, not set on
fire or exploded by the detonator of the shell, not decomposed by water,
not readily absorbed, stable enough to stand storage for six months and
capable of being manufactured by the thousands of tons. No one gas will
serve all aims. For instance, phosgene being very volatile and quickly
dissipated is thrown into trenches that are soon to be taken while
mustard gas being very tenacious could not be employed in such a case
for the trenches could not be occupied if