396 
NATURE 
_ [JUNE 10, 1915 

have been or are likely to be used may be of 
service at the present time. 
The chemical laboratory would be able to pro- 
vide a very large number of offensive and 
poisonous gases and vapours, but for practical 
purposes they would be limited to those which 
present the following qualities: (1) they must be 
much heavier than atmospheric air; (2) they must 
be producible in large quantity in the form of a 
portable liquid or solid, which in its turn will 
evaporate rapidly from the containing vessel or 
otherwise so as to produce the gas; (3) they should 
not be excessively soluble in water, or much would 
be lost in rolling over moist ground. 
In the newspaper accounts from eye-witnesses 
of the cloud of gas sent out by the enemy it 
has several times been described as presenting a 
reddish colour. If this statement is based on 
correct observation it is certain that the gas used 
on these occasions must have contained either 
bromine or peroxide of nitrogen, both of which 
have an orange-brown colour. It seems improb- 
able that oxides of nitrogen would be used on 
account of the cost in the form of nitric acid or 
nitrate from which they must be produced. 
Bromine, however, is made from the salts in the 
Stassfurth deposits, and from this source up to 
the outbreak of war much of the bromine and 
bromides of commerce was obtained. Bromine 
is at common temperatures a liquid, but it evapor- 
ates very easily and produces a vapour which is 
about five-and-a-half times heavier than air. 
Probably the amount of bromine available would 
be insufficient for the production of the enormous 
quantities of vapour requirea in these operations 
if used by itself, but as the whole object of 
manufacture in the present case is not the pro- 
duction of pure bromine but of something that 
will suffocate, the material used may consist 
essentially of the closely allied element chlorine, 
accompanied with a quantity of bromine sufficient 
to account for the colour. 
At ordinary temperatures chlorine is a pale-green 
gas which is about two-and-a-half times heavier 
than air. The gas was discovered by the Swedish 
chemist Scheele in 1774, and has been used for 
bleaching purposes since the end of the eighteenth 
century. It acts rapidly on nearly all metals if 
moist, but when free from water it does not attack 
the surface of iron, and as it is easily reduced by 
compression to a liquid, it has been produced 
commercially in very large quantities for many 
years past in the liquid state and preserved in 
iron bottles. There can be littie doubt that the gas 
from which our men have been suffering is sent 
into the trenches in such cylinders. The gaseous 
chlorine which escapes from them on simply open- 
ing the tap, whether or not it is accompanied 
with bromine, is quite sufficient to account for the 
suffering and death which have been the result of 
getting the gas into the lungs, but other volatile 
substances have been suggested as_ possibly 
available. Thus phosgene, a compound of car- 
bonic oxide and chlorine, is a heavy gas about 
three-and-a-half times heavier than air, easily 
NO. 2380, VOL. 95] 


liquefiable and easily vaporisable from the liquid, 
which is a commercial article produced in 
Germany on a fairly large scale. Sulphur dioxide, 
often erroneously called surphurous acid, is 
familiar as the product of burning sulphur, and 
being liquefiable readily it may be seen in the 
liquid form in glass siphon bottles in every 
chemical laboratory. 
The chlorides of sulphur, phosphorus, and 
arsenic are also very irritating and poisonous. The 
only reason for supposing that these compounds 
might be employed is provided by a communica- 
tion from Warsaw which appeared in the Times 
of June 5, in which it is stated that the Germans 
had been burning straw on which a white powder 
resembling salt had been sprinkled. The dense 
smoke carried by the wind over the Russian lines 
is stated to have produced symptoms similar to 
| those reported from France in the case of victims 
of suffocation from what is believed to be chlorine 
or a mixture of chlorine and bromine. The white 
powder used against the Russians probably con- 
tains one of the chlorides mentioned above, which 
might be made portable by admixture of common 
salt. The statement in the Times that the powder 
is believed to be some easily-made compound of 
chloral is obviously a misprint. 
Fortunately all these fumigating agents agree 
in one particular. They can be absorbed and 
therefore stopped by passage through or over a 
strongly alkaline substance te which may be added, 
especially in reference to chlorine or bromine, a 
proportion of sodium hyposulphite (thiosulphate), 
the familiar “hypo” of the photographer. It is. 
important to notice that a strong alkali is necessary 
and in layers sufficiently thick. When the ordinary 
housekeeper speaks of “carbonate of soda,” the 
salt known to the chemist as bicarbonate is 
always intended, and this is almost useless. 
The masks or respirators supplied to the 
troops consist of material saturated, though not 
dripping, with a strong solution of common 
washing soda (the carbonate) mixed with an equal 
quantity of hyposulphite, to which has been added 
2 or 3 per cent. of glycerine to keep the whole 
damp. A very good material would also be the 
granular mixture of lime and caustic soda, known 
in every chemical laboratory as “soda-lime.” This. 
would have to be wrapped up in gauze and would 
not require to contain glycerine. 
Many well-intentioned efforts have been made 
by private persons to supply their soldier friends 
with respirators made of gauze or muslin con- 
taining a receptacle filled with cotton waste 
saturated with an alkaline solution. Most of 
these attempts are not only imperfect but really 
dangerous to the men by leading them to consider 
themselves protected when practically there is no 
protection. The pads saturated with alkali are 
often much too small, and the cotton padding has 
not been secured in position by proper quilting 
or otherwise. Moreover, the most efficient solution 
has not been used. The official protectors take the 
form of a hood which covers the head and afford 
a complete protection against the gases, even 
