286  War  Chemistry  and  Medicine.  {Am'^u%^rnL 
other  noxious  substances  employed  by  our  enemies  in  their  warfare3 
early  taxed  the  ingenuity  of  all  the  Allies  to  devise  satisfactory 
respirators.  At  first  an  alkaline  solution  was  sufficient  to  protect 
against  inhalation  of  chlorin ;  but  when  phosgene,  prussic  acid,  xylyl 
bromide,  chlorpicrin,  bromacetone  and  a  succession  of  other  equally 
formidable  products  had  to  be  taken  into  account,  cheesecloth  im- 
pregnated with  alkali  or  even  with  sodium  phenate  and  hexamthylen- 
amine  no  longer  saved  the  wearer  of  the  mask  from  untoward 
effects;  The  soda-lime  finally  developed  and  used  in  masks  con- 
tained lime,  cement,  infusorial  earth,  sodium  hydroxide,  sodium 
permanganate  and  water.  Each  ingredient  performed  a  definite 
function.  The  lime  furnished  the  main  part  of  the  absorption  for 
acid  gases,  which  it  neutralizes,  generally  with  the  formation  of  cal- 
cium chloride.  The  cement  is  used  to  make  the  granules  suffi- 
ciently hard  and  yet  not  decrease  the  porosity,  which  is  fatal  to 
good  absorption.  Several  other  binders  give  equally  good  hardness, 
but  all  destroy  the  porosity.  The  infusorial  earth  is  used  to  increase 
the  porosity  of  the  granules  and  thus  permit  the  gas  to  have  access 
to  the  interior  and  utilize  the  full  absorptive  capacity  of  the  granule. 
The  sodium  hydroxide  activates  the  rate  of  absorption  of  most 
gases,  and,  in  addition,  makes  the  control  of  the  drying  process  more 
simple  and  tends  to  maintain  the  proper  water  content  in  the  finished 
granule.  The  sodium  permanganate  is  used  primarily  to  oxidize 
certain  oxidizable  gases,  which  are  difficult  to  absorb  in  gas  masks. 
The  water  is  necessary  in  making  up  a  satisfactory  mixture,  and, 
after  drying,  a  fairly  definite  moisture  content  is  needed  to  get  the 
best  results  in  the  absorption  of  gases. 
Xor  is  the  story  of  prophylactic  measures  against  chemical  modes 
of  warfare  completed  with  the  description  of  the  gas  masks.  Since 
most  of  the  casualties  from  the  widely  used  mustard  gas  were  due 
to  skin  burns,  it  became  necessary  to  devise  suitable  protective  cloth- 
ing. Gummed  suits  might  be  appropriate  in  winter,  but  they  be- 
came a  physiologic  impossibility  in  hot  days.  Yet  even  this  handi- 
cap was  finally  overcome  by  the  designing  of  suits  that  were  not 
impermeable  to  air  and  moisture,  yet  absorbed  mustard  gas  vapor. 
Some  day  an  orderly  account  of  the  almost  infinite  variety  of 
chemical  problems  that  the  government  was  called  on  to  answer  in 
this  war  will  be  written.    It  will  be  a  story  of  fascinating  interest. 
3  "War  Gases  and  Chemical  Warfare,"  editorial,  /.  A.  M.  A.,  71,  1742, 
f  November  23),  1918. 
