326     PREPARATIONS  OF  THE  U.  S.  PHARMACOPOEIA,  1860. 
EEMAEKS  ON  SOME  PREPARATIONS  OF  THE  TJ.  S.  PHAR- 
MACOPOEIA OF  1860.  (FERRUM.) 
By  William  Procter,  Jr. 
[(Continued  from  p.  406,  vol.  xiii.) 
Ferri  Chloridum. — Perhaps  no  one  of  the  new  formulae  of  the 
Pharmacopoeia  was  more  called  for  by  the  progress  of  thera- 
peutics than  that  for  this  salt.  Its  frequent  prescription  in  a 
solid  form  to  make  extemporaneous  solutions  and  syrups  of 
chloride  of  iron  renders  it  necessary  to  have  a  salt  that  will  dis- 
solve wholly  in  water,  and  this  want  the  officinal  chloride  com- 
pletely satisfies,  being  the  duodecimal  hydrate  Fe2  Cl3  +  12HO. 
In  examining  specimens  of  the  commercial  salt,  it  is  occasionally 
met  with  in  a  condition  unfit  for  effecting  solutions,  without 
filtration ;  due  to  the  effect  of  heat  in  evaporation,  a  portion  of 
the  chloride  being  decomposed,  and  sesquioxide  or  subchloride 
remaining. 
The  process  of  the  Pharmacopoeia  is  modelled  after  that  of 
Wittstein.  Two  equivalents  of  iron  are  dissolved  in  two  equiva- 
lents of  hydrochloric  acid  to  obtain  two  equivalents  of  neutral 
protochloride  of  iron  in  the  filtered  solution ;  one  equivalent  of 
hydrochloric  acid  is  then  added  to  supply  an  equivalent  of  chlo- 
rine ;  the  mixture  being  now  raised  to  the  boiling  point  is  con- 
verted into  sesquichloride  by  the  action  of  the  nitric  acid,  which, 
in  supplying  oxygen  to  the  hydrogen  of  the  hydrochloric  acid, 
liberates  its  chlorine  under  circumstances  favorable  for  union 
with  the  chloride  of  iron  to  form  sesquichloride.  The  next  step 
in  the  process  is  the  isolation  of  the  salt  from  the  excess  of 
water  :  this  is  effected  by  a  gentle  sand-bath  heat,  until  the  con- 
tents of  the  capsule,  which  should  be  previously  tared,  weighs 
"  eight  troy  ounces  and  three  hundred  and  sixty  grains,"  when 
eight  troy  ounces  of  hydrochloric  acid  are  used  to  act  on  the 
iron.  It  is  then  removed  from  the  bath  and  set  aside,  covered 
with  a  bell  glass  for  several  days  in  a  dry  place,  until  the  whole 
becomes  a  solid  crystalline  mass,  in  the  form  of  mammillary  con- 
cretions of  crystals.  This  should  be  kept  in  well-stopped  bottles, 
of  the  size  suited  to  dispensing  purposes. 
In  directing  the  evaporation  to  a  specified  weight,  it  is  on  the 
basis  of  the  acid  being  of  Pharmacopoeia  strength,  sp.  gr.  1.16. 
