NEW  PROCESS  FOR  PREPARING  POWDER  OF  IRON.  451 
copoeias  already  mentioned,  the  process  is  difficult  and  uncertain; 
it  consists  of  passing  a  stream  of  hydrogen  gas  over  oxide  of  iron, 
heated  to  redness,  in  an  iron  tube.  The  chief  difficulty  consists 
in  regulating  the  heat,  for  if  the  heat  is  not  sufficiently  high  the 
product  will  be  a  pyrophorous,  taking  fire  immediately  on  expo- 
sure to  the  air  ;  and,  on  the  other  hand,  if  the  heat  be  too  high, 
the  powder  will  become  agglutinated.  These  difficulties  cause 
this  preparation  to  fetch  a  high  price,  and  afford  temptations  to 
the  substitution  of  spurious  imitations. 
By  the  process  which  I  propose,  these  difficulties  are  overcome, 
and  an  opportunity  will  be  afforded  of  determining,  by  extensive 
use,  whether  the  remedial  effects  of  this  preparation,  justify  its 
addition  to  our  already  overstocked  materia  medica. 
To  prepare  powder  of  iron,  according  to  my  plan,  the  steps  to 
be  pursued  are  as  follows  : — 
Eight  ounces  of  yellow  prussiate  of  potash  are  to  be  heated  in 
an  oven  till  the  water  of  crystallization  is  driven  off,  reduced  to 
a  very  fine  powder,  then  thoroughly  mixed  with  four  ounces  of 
red  oxide  of  iron  (previously  well  washed  and  finely  pulverized), 
and  three  ounces  of  pure  dried  carbonate  of  potash.  This  mixture 
is  then  to  be  introduced  (a  small  portion  at  a  time)  into  a  crucible 
previously  heated  to  low  redness.  The  heat  must  be  kept  up  till 
all  appearance  of  effervescence  has  ceased.  The  crucible  is  then 
allowed  to  cool,  the  mass  scooped  out,  powdered,  and  having 
been  introduced  into  a  large  bottle,  repeatedly  washed,  by  agita- 
tion and  decantation,  with  distilled  water,  till  the  washings  cease 
to  precipitate  with  solution  of  nitrate  of  silver.  The  powder  is 
then  to  be  turned  out  on  a  filter  and  dried  as  rapidly,  and  with, 
as  little  exposure  to  air,  as  possible.  It  may  now,  if  necessary, 
be  passed  through  a  fine  sieve,  to  separate  any  particles  which 
may  have  agglutinated,  owing  to  the  application  of  too  high  a 
heat.  The  powder  should  be  preserved  in  a  well-stopped  bottle. 
With  this  process,  and  the  quantities  mentioned,  the  product  ob- 
tained will  weigh  about  three  ounces  and  a  half. 
As  thus  obtained  the  reduced  iron  is  a  fine  powder,  of  a  dark 
grey  color,  not  feeling  gritty  or  coarse  under  the  fingers  ;  it  dis- 
solves completely  in  muriatic  acid,  with  considerable  effervescence, 
and  the  solution  thus  obtained  yields  with  potash  or  ammonia  the 
greenish  gelatinous  precipitate  indicative  of  a  protosalt.  If  the 
precipitate  be  reddish,  it  shows  the  powder  to  contain  oxide  of 
