^4  Oxidation  of  Ferrous  Salts  at  Low  Temperatures,  \  ^""VebTiss^^""' 
THE  OXIDATION  OF  FERROUS  SALTS  AT  LOW 
TEMPERATURES. 
By  F.  L.  Slocum. 
Read  at  the  Pharmaceutical  Meeting  January  zo: 
There  appeared  in  this  journal  for  March,  1879,  page  141,  a  new 
process  for  the  preparation  of  solution  of  perchloride  of  iron,  without  the 
aid  of  heat,  by  adding  the  acid  solution  of  ferrous  chloride  to  the  requi- 
site quantity  of  nitric  acid. 
In  the  Journal  for  December,  1879,  page  587,  is  a  verification  of  the 
successful  application  of  this  process,  and  a  like  happy  result  is  reported 
with  Monsel's  solution,  by  the  same  procedure. 
At  the  request  of  Prof.  Maisch,  and  under  his  directions,  1  made 
numerous  experiments  with  the  following  results  : 
Liquor  Ferri  Perchloridi. — The  acid  solution  of  the  ferrous  chloride 
and  the  nitric  acid  had  a  temperature  of  78°F.,  the  temperature  of  the 
room  \  on  slowly  adding  the  acid  ferrous  chloride  to  the  nitric  acid  the 
temperature  rose  to  I20°F.  Oxidation  was  quite  energetic,  and  nitrous 
fumes  were  given  off  constantly  without  foaming.  When  about  two- 
thirds  of  the  ferrous  chloride  was  oxidized  the  temperature  had  receded 
to  I05°F.,  and  oxidation  was  hardly  perceptible,  and  when  the  whole 
of  the  ferrous  chloride  had  been  added,  which  required  about  fifteen 
minutes'  time,  the  temperature  of  the  solution  had  receded  to  85 ^F. 
After  standing  a  while  the  solution  acquired  a  color  similar  to  the 
officinal  liquor,  but  owing  to  the  great  range  of  temperature  it  passed 
through  in  oxidizing,  several  nitrogen  oxides  were  formed  and  remained, 
contaminating  the  solution  ;  complete  oxidation  was  not  effected,  and 
it  is  next  to  impossible  to  free  the  solution  from  nitrogen  compounds. 
After  making  numerous  experiments,  each  time  using  a  little  higher 
temperature  to  begin  with  and  a  slight  modification  of  the  process,  the 
following  was  found  to  be  a  very  practicable  process,  and  the  lowest 
temperature  that  could  be  used  to  get  at  correct  results  : 
Mix  the  nitric  and  reserved  hydrochloric  acid  in  an  evaporaring  or 
suitable  basin,  heat  them  to  a  temperature  of  I40°F.,  and  filter  into 
the  mixed  acids  the  solution  of  ferrous  chloride  previously  heated  to 
i8o°F.;  stir  the  solution  while  the  liquids  are  mixing  ;  oxidation  takes 
place  gradually  and  completely,  the  temperature  rising  to  i6o^F.  or 
i65°F.  There  is  no  accumulation  and  sudden  expulsion  of  nitrous 
fumes  causing  foaming,  as  in  the  officinal  process.    The  result  is  an 
