272  Use  of  Copper  in  Destroying  Typhoid.     { Am jJUne?iSSarm* 
THE  ELIMINATION  OF  COPPER  FROM  WATER. 
Nageli1  discovered  during  the  course  of  his  experiments  that  a 
solution  of  copper  that  was  toxic  to  Spirogyra  could  be  rendered 
harmless  by  the  introduction  of  a  number  of  more  or  less  insoluble 
substances.  Among  those  which  he  used  for  this  purpose  were  the 
following  :  Sulphur  (either  roll  or  flowers),  carbon  (either  graphite 
or  soot),  coke,  coal,  peat,  black  oxide  of  manganese,  starch,  cellu- 
lose (either  as  Swedish  filter-paper,  or  cotton,  linen  or  wood  fiber), 
silk,  wool,  stearic  acid,  paraffin,  gum,  dextrin,  egg  albumin,  glue. 
True  and  Oglevee2  have  studied  the  influence  of  insoluble  sub- 
stances on  the  toxic  action  of  poisons  in  solution,  and  have  not 
only  confirmed  Nageli's  observation,  but  have  shown  that  sand  and 
powdered  glass  have  the  property  of  reducing  the  toxicity  of  solu- 
tions of  copper.  Moore  and  Kellerman  have  shown  in  their  recent 
bulletin  the  relative  decrease  of  the  toxicity  of  copper  sulphate 
solutions  according  to  the  amount  of  organic  matter  present, 
the  amount  of  carbon  dioxide  dissolved  in  the  water,  or  the  tempo- 
rary hardness  of  the  water. 
In  addition,  the  copper  is  absorbed  by  the  organisms  which  are 
killed,  and  is  thus  eliminated.  It  is,  therefore,  apparent  that  there 
are  a  number  of  ways  by  which  the  copper  is  removed  from  solu- 
tion and  the  toxicity  of  solutions  containing  it  lessened. 
In  the  case  of  reservoirs  treated  with  copper  it  is  likely  that  none 
or  very  little  copper  remains  in  solution  for  any  considerable  period 
of  time.  By  a  combination  of  factors,  such  as  (a)  absorption  by  the 
organisms  that  are  killed  as  well  as  by  other  organic  matter;  {&) 
by  the  formation  of  insoluble  compounds  with  various  inorganic 
salts ;  and  (c)  by  adsorption  by  various  insoluble  materials,  the 
copper  is  removed,  so  that  by  the  time  the  water  reaches  the  con- 
sumer there  is  probably  no  copper  in  solution,  and  the  insoluble 
copper,  if  present,  is  necessarily  more  or  less  inert.  Furthermore,  I 
am  of  the  opinion  that  there  is  more  copper  in  solution  in  home- 
filtered  water  which  has  been  treated  with  copper  foil  than  in  the 
water  which  reaches  the  consumer  after  treatment  of  a  large 
reservoir  with  copper  sulphate  in  the  quantities  proposed  by  Moore 
and  Kellerman  for  the  purpose. 
1  Loc.  cit. 
2  Botanical  Gazette,  39,  1905,  pp.  1-21. 
