Am.  Jour.  Pharm. 
April,  191 8. 
Methods  of  Gas  Warfare. 
265 
The  concentrations  of  gas  usually  met  with  are  really  very  low. 
As  has  been  said,  a  high  concentration  for  a  gas  cloud  is  1  part  in 
1,000,  whereas  concentrations  of  two  or  three  per  cent,  can  be  met 
by  respirators  depending  on  chemical  reactivity.  One  such  respira- 
tor is  a  box  of  chemicals  connected  by  a  flexible  tube  with  a  face- 
piece  fitting  around  the  contours  of  the  face,  and  provided  with  a 
mouthpiece  and  nosepiece. 
As  regards  the  chemicals  used  there  is  no  secret,  for  the  Ger- 
mans have  many  of  the  same  things.  Active  absorbent  charcoal  is 
one  of  the  main  reliances,  and  is  another  suggestion  that  we  owe 
to  the  Russians.  Wood  charcoal  was  used  in  one  of  their  devices 
and  was  effective,  but  most  of  the  Russian  soldiers  had  no  protec- 
tion at  all. 
We  wanted  to  protect  against  chlorine,  acids  and  acid-forming 
gases,  phosgene,  etc.,  and  at  one  time  were  fearful  of  meeting  large 
quantities  of  hydrocyanic  (prussic)  acid  (HCN).  At  one  period 
every  prisoner  taken  talked  about  the  use  of  prussic  acid,  saying 
that  the  Kaiser  had  decided  to  end  the  war  and  had  given  permis- 
sion to  use  prussic  acid.  Protection  was  evidently  needed  against 
it.  The  three  things  that  then  seemed  most  important  were:  (1) 
chlorine  and  phosgene;  (2)  prussic  acid;  (3)  lachrymators.  Char- 
coal and  alkaline  permanganate  will  protect  against  nearly  every- 
thing used,  even  up  to  concentrations  of  ten  per  cent,  for  short 
periods. 
The  German  apparatus,  developed  about  the  same  time,  is  of 
different  pattern,  and  is  still  employed.  It  consists  of  a  small  drum, 
attached  directly  to  the  front  of  the  face-piece,  and  weighs  less 
than  the  British  respirator  but  must  be  changed  more  frequently. 
It  has  no  mouthpiece.  The  chemicals  are  in  three  layers :  first  an 
inside  layer  of  pumice  with  hexamethylenetetramine,  in  the  middle 
a  layer  of  charcoal  (sometimes  blood  charcoal),  and  outside  baked 
earth  soaked  in  potassium  carbonate  solution  and  coated  with  fine 
powdered  charcoal. 
As  regards  the  future  of  the  gas  cloud,  it  may  be  looked  upon 
as  almost  finished.  There  are  so  many  conditions  that  have  to  be 
fulfilled  in  connection  with  it  that  its  use  is  limited.  It  is  very 
unlikely  that  the  enemy  will  be  able  to  spring  another  complete  sur- 
prise with  a  gas  cloud. 
The  case  is  different  with  gas  shells.  The  gas  shells  are  the 
most  important  of  all  methods  of  using  gas  on  the  Western  Front, 
