^mMayy'i9oiarm"}  Liquid  Carbonic  Acid  Gas.  237 
The  appearance  of  the  above  exposures  upon  development  was 
as  follows : 
1.  Faint  image  appeared  gradually  fading  and  leaving  a  fog. 
2.  Image  appeared,  but  upon  further  development  became  very 
slightly  foggy. 
3.  4,  5  and  6  showed  very  little  difference  in  density  or  detail. 
LIQUID  CARBONIC  ACID  GAS. 
HOW  IT  IS  MADE  AND  PUT  UP  FOR  SODA  FOUNTAIN  USE. 
By  Frederick  T.  Gordon. 
How  many  druggists  are  there  who  know  how  the  liquid  gas 
they  are  now  using  for  charging  their  soda  water  is  made,  or  how  it 
is  put  into  the  heavy  iron  "tanks"  in  which  they  have  it  delivered 
to  them  ?  Now  that  this  liquid  gas  is  rapidly  supplanting  the  old 
way  of  making  gas  in  the  cellar  from  various  materials  or  even  the 
buying  of  soda  water  already  charged,  there  is  every  reason  why  the 
druggist  should  know  the  ins  and  outs  of  his  supply  if  he  would  be 
able  to  talk  intelligently  on  it  to  the  inquiring  customer.  And  this 
is  easy  to  do,  too,  for  the  whole  operation  of  making  the  gas,  lique- 
fying it  and  filling  the  fountain  tanks,  is  very  simple  and  easily 
understood. 
Liquid  carbon  dioxide  is  now  as  much  a  matter  of  commerce  as 
is  carbonate  of  soda,  and  there  are  a  number  of  firms  in  this  country 
making  it,  from  many  different  materials  and  in  many  different 
ways.  The  manufacture  of  the  gas  may  be  classed  under  three 
general  processes :  Driving  off  the  C02  by  heat  from  various  car- 
bonates, such  as  limestone,  dolomite,  etc.;  this  is  a  process  that  is 
confidently  stated  by  authorities  to  be  the  one  that  promises  the  best 
returns  in  the  future  ;  formation  of  the  gas  by  the  interaction  of 
acids  on  carbonates  is  another,  the  most  common  of  which  are  the 
use  of  marble  and  sulphuric  acid  and  bicarbonate  of  soda  and 
sulphuric  acid  ;  while  the  collection  of  the  gas  formed  in  breweries 
by  fermentation  or  from  burning  coke  or  coal  is  a  process  that  is 
rapidly  assuming  great  importance.  Considerable  C02  is  now 
collected  from  the  natural  spring  waters  at  different  points,  the 
largest  manufactory  of  this  kind  being  at  Saratoga  Springs,  New 
York. 
