126  EFFECT  OF  TEMPERATURE  ON  ORGANIC  MATTER  IN  WATER. 
easily  prepared  by  adding  a  solution  of  protosulphate  of  iron  to 
an  excess  of  oxalate  of  ammonia  solution  containing  a  little  free 
oxalic  acid,  a  yellow  precipitate  is  thrown  down,  which  is  the 
compound  in  question;  this  should  be  well  washed  and  then 
dried.  By  having  an  excess  of  oxalic  acid  present  any  per-salt 
formed  is  held  in  solution.  The  precipitate  yielded  on  analysis 
results  agreeing  with  the  formula  Fe  0,  C2  03+4HO,  and  there- 
fore contains  one-third  of  its  weight  of  oxide  of  iron,  one-third 
of  oxalic  anhydride,  and  the  rest  of  water.  The  salt,  when 
prepared  as  above  directed,  is  a  fine  powder  of  a  straw-yellow 
color,  almost  devoid  of  taste  and  singularly  slow  to  oxidize  in 
contact  with  the  air.  It  is  slightly  soluble  in  water,  but  more 
easily  acted  upon  by  a  dilute  acid,  and  is  decomposed  by  the 
alkalies  of  their  carbonates.  When  burned  in  the  open  air  it 
leaves  a  residue  of  pure  peroxide  of  iron  in  a  condition  particu- 
larly favorable  for  the  production  of  fer  reduit.  In  conclusion, 
I  may  remark  that  the  oxalate  of  iron  requires  but  three  atoms 
of  oxygen  for  its  complete  oxidation  in  the  system,  whereas  for 
a  given  weight  of  iron  the  tartrate  of  the  peroxide  needs  ten 
equivalents,  and  the  citrate  eighteen  of  oxygen,  to  effect  the 
same  end."* — Pharm.  Journal,  Jan.  1867. 
ON  THE  EFFECT  OF  TEMPERATURE  ON  ORGANIC  MAT- 
TER IN  WATER. 
Dr.  Frankland  writes : — "  With  regard  to  the  temperature  at 
which  the  putrefaction  and  decay  of  organic  matter  in  water 
take  place,  I  find  that  the  following  is  all  that  appears  in  the 
printed  report  of  my  evidence  on  the  subject  in  the  case  i  Duke 
of  Buccleuch  and  others  v.  Alexander  Cowan  and  others,'  re- 
cently tried  at  Edinburgh.  *  Where  a  river  becomes  sluggish — 
as  where  it  is  pent  up  by  a  weir — the  quantity  of  organic  mat- 
ter, and  also  of  mineral  matter,  increases  in  some,  cases  very 
considerably ;  but  that  is  only  the  case  in  warm  weather, 
and  the  'temperature  of  the  water  must  be  55°  Fahrenheit  and 
upwards,  for  this  effect  to  be  produced.    The  putrefaction  of  the 
*[This  salt  has  been  recommended  as  a  chalybeate  by  Prof.  Craig,  of 
the  Smithsonian  Institution  as  far  back  as  1858. — Ed.  Am.  Jour.  Pharm.] 
