Riddle of the Rhine | Page 9

The best known

substances of this type was chlorine, employed in the liquid state in
cylinders on the occasion of the first German gas attack, but the most
formidable were phosgene (an important substance required in the
manufacture of dyes), diphosgene, chlor-picrin, made from bleaching
powder and picric acid, brom-acetone, which was also a powerful
lachrymator, and diphenylchlorarsine, known as sneezing gas, the first
sternutatory or sneezing compound to appear on the front in large
quantities. The toxic compounds were so called because of their
specific effect upon particular parts of the organism such as, for
example, the nervous system. The chief example, with regard to the
military value of which there has been much dispute, was prussic, or
hydrocyanic, acid. The French had definite evidence of the mortal
effect of this compound upon German gunners, but it was doubted by
other Allies whether French gas shell produced a sufficient
concentration of gas to be of military value. It was a kill or cure
compound, for recovery was rapid from any concentration which did
not produce death.
A prominent Cambridge physiologist, in the heat of the controversy on
this matter, made a very brave and self-sacrificing experiment. He
entered a chamber of prussic acid which was sufficiently concentrated
to cause the death of other animals which were present. They were
removed in time, and he escaped because the concentration was not a
mortal one for man. This was, in a sense, an _experimentum crucis_
and, although it did not disprove the extreme danger of prussic acid, if
employed in high concentrations, it showed, on the other hand, that it
was difficult to gauge the military value by field experiments; battle
results were necessary. The Germans' disappointment with the use of
arsenic compounds confirms this need for battle evidence.
Lachrymators.--There is hardly need to dwell on the next class, the
lachrymator. These compounds were employed on a large scale to
produce temporary blindness by lachrymation, or weeping. We give
later some interesting examples of their use on the front. It is an
arresting thought that even as early as 1887 Professor Baeyer, the
renowned organic chemist of Munich, in his lectures to advanced
students, included a reference to the military value of these compounds.

Vesicant or Blistering Compounds.--It was the introduction of the
fourth, the vesicant class, which revealed, more than any other enemy
move, the great possibilities inherent in chemical warfare. These
compounds, the chief of which was mustard gas, produced vesicant, or
skin burning, effects, which, although rarely mortal, were sufficient to
put a man out of action for a number of months. Mustard gas resulted
from pure scientific investigation as early as 1860. Victor Meyer, the
famous German chemist, described the substance in 1884, indicating its
skin-blistering effects. There is evidence of further investigation in
German laboratories a year before the outbreak of war, and whatever
the motive for this work, we know that mustard gas must have received
the early attention of the German War Office, for it was approved and
in production early in 1917. Although the Medecin aide-major
Chevalier of the French services drew attention to its importance in
1916, the French had no serious thought of using mustard gas, and did
not realise its possibilities until the German battle experiment of July,
1917. It is not generally known, however, that other vesicant
compounds were employed, notably some of the arsenic compounds,
and the Germans were researching on substances of this nature which
gave great promise of success. Mustard gas provides a striking example
of the organic way in which chemical warfare is bound up with the dye
industry. The compounds required for its manufacture were those
which had been made on a large scale by the I.G. for the production of
indigo. World indigo monopoly meant possession of a potential
mustard gas surprise on the outbreak of war.
Sneezing or Sternutatory Substances.--The last class, the sternutatory
substances, produced the familiar sneezing effect which was
accompanied by intense pain and irritation of the nose, throat, and
respiratory channels. They were mostly arsenic compounds and were
not only sternutatory but also toxic, producing the after effects of
arsenic poisoning.
The Tactical Classification.--From the point of view of our account of
chemical warfare, however, the physiological classification of these
substances is not so important as the tactical and, indeed, once this
grouping of the substances is understood, a profound knowledge of

their chemical nature is not necessary.
Persistent Substances.--Two main classes exist from the tactical Point
of view. There are those "persistent" substances which remain for a
long time on the soil or on the object on which they are sprayed by
shell, while retaining their dangerous effect. Mustard gas was the chief
example, but some of the lachrymators were just as persistent. By their
use it is possible to