ANTIDOTE  AT  ONCE  FOR  PRUSSIC  ACID,  ETC. 
15 
shown  by  using  hydrate  of  magnesia  instead.  In  this  case, 
even  with  a  much  smaller  quantity  of  tartar  emetic,  the  filtered 
liquid  gives  antimony  in  abundance  to  the  proper  tests. 
To  be  suitable  for  the  antidotes,  the  liquor  ferri  perchloridi 
must  answer  to  the  following  tests  : — one  fluid  drachm  must  con- 
tain 15*62  grains  peroxide  of  iron  ;  ammonia  must  give  a  pure 
reddish-brown  precipitate,  without  any  shade  of  black ;  it  must 
not  smell  strongly  acid,  nor,  after  slight  dilution,  give  a  brisk 
effervescence  with  a  piece  of  zinc. 
Directions  proposed  to  be  attached  to  each  bottle  of  Liq.  ferri 
Perchloridi : — 
Prussia  acid  antidote. — Take  of  liquor  of  pcrchloride  of  iron 
thirty-seven  minims,  protosulphate  of  iron  in  crystals,  as  pure 
as  possible,  twenty-five  grains ;  as  much  water  as  make  a  solu- 
tion of  a  protosesquisalt  of  iron,  measuring  about  half  an  ounce. 
Dissolve,  on  the  other  hand,  seventy-seven  grains  crystallized 
carbonate  of  soda  in  about  half  an  ounce  of  water.  These 
quantities  destroy  the  poisonous  action  of  between  100  and  200 
minims  of  medicinal  prussic  acid,  officinal  strength,  on  giving 
first  the  one  liquid  and  then  the  other. 
Antidote  for  cyanide  of  potassium. — The  antidote  for  this 
compound  is  the  same  as  for  prussic  acid,  except  that  the  solu- 
tion of  protosesquisalt  of  iron  is  to  be  used  without  the  alkaline 
solution,  the  prussic  acid  being  already  combined  with  an  alkali ; 
the  use  of  the  alkali,  however,  would  not  be  injurious ;  a  harm- 
less yellow  prussiate  would  be  formed.  In  this  case,  in  conse- 
quence of  the  possible  presence  of  free  acid  in  the  stomach,  the 
alkaline  liquid  should  be  given  first — the  quantities  given,  as  the 
prussic  acid  antidote  would  decompose  thirty-five  grains  of  cyanide 
of  potassium. 
Antidote  for  arsenious  acid. — Measure  out  five  fluid  drachms 
and  seven  minims  of  liquor  ferri  perchloridi  into  two  or  three 
ounces  of  water,  then  add  to  the  liquid  a  solution  of  one  ounce 
of  crystallized  carbonate  of  soda  in  a  few  ounces  of  warm  water, 
stir  till  effervescence  ceases  ;  the  resulting  mixture  destroys 
about  ten  grains  of  arsenious  acid. 
Antidote  for  tartar  emetic. — Mix  five  fluid  drachms  and  seven 
minims  of  liquor  ferri  perchloridi  with  a  few  ounces  of  water ; 
