POISONOUS  EFFECT  FROM  COPPER  FOUNTAINS.  423 
The  substance  which  first  attracted  attention  was  copper. 
This  was  very  abundant  in  soda  water  obtained  from  several 
obscure  shops,  where  it  was  presumed  the  traffic  was  limited,  and 
consequently  the  acid  water  remained  longer  in  the  copper  con- 
densers. It  was  so  evident  that,  on  boiling  off  the  excess  of 
carbonic  acid  gas,  a  green  scum  made  its  appearance,  which,  on 
further  evaporation,  settled.  This  was  carbonate  of  copper,  pre- 
viously held  in  solution  by  the  carbonic  acid. 
The  amount  of  metallic  copper  in  a  quart  was  one  grain  and 
a  half! 
Soda  water  obtained  from  the  same  establishment  on  different 
days,  was  found  to  contain  varying  amounts  of  the  poisonous 
carbonate. 
The  source  of  this  copper,  and  the  cause  of  these  differences, 
may  be  accounted  for  in  several  ways. 
The  copper  condensers  purport  to  be  tinned  internally ;  but 
where  they  have  been  in  use  a  long  time,  the  tin,  by  chemical 
and  mechanical  action,  has  been  removed,  at  least  in  part ;  thus 
exposing  a  surface  of  copper  to  the  corrosive  action  of  the  car- 
bonic acid,  aided  by  sulphuric  acid,  which  is  occasionally  found 
in  the  soda  water. 
Although  the  carbonate  of  copper  is  insoluble  in  pure  water, 
it  is  capable  of  being  held  in  solution  in  water  highly  charged 
with  carbonic  acid  gas  for  the  soda  water  which  yields  this  green 
scum  after  discharging  the  gas,  is  clear  and  colorless  previous  to 
the  operation. 
The  soda  water  drawn  shortly  after  charging  the  condenser, 
would  necessarily  yield  less  copper  on  analysis,  than  that  obtained 
from  the  same  fount  after  having  several  days  to  exert  its  cor- 
rosive influence.  Again,  the  tinning  (for  all  are  professedly  thus 
lined)  would  be  more  perfect  in  some  than  in  others — dependent 
not  only  on  the  length  of  time  the  condensers  have  been  used, 
but  also  on  the  completeness  of  the  original  coating.  I  have 
been  informed  that,  in  order  to  facilitate  the  flow  of  the  tin,  soft 
solder  is  at  times  resorted  to,  or  the  copper  is  washed  with  a  salt 
of  mercury.  Under  these  circumstances,  the  chemical  and  elec- 
trical action  would  be  rather  complicated,  and  the  soda  water 
possessed  of  remarkable  medicinal  virtues. 
The  second  poisonous  compound  which,  from  its  abundance. 
