ON  TINCTURA  FERRI  CHLORIDI,  U.  S.  P.  447 
the  U.  S.  P.  formula,  here  given  will  show.  The  recipe  is  as 
follows  : — 
"  Take  of  Iron  in  the  form  of  wire  and  cut  in  pieces  three  troy- 
ounces  ;  Muriatic  Acid  seventeen  and  a  half  troyounces  ;  Alcohol 
three  pints  ;  Nitric  Acid,  Distilled  Water,  each,  a  sufficient  quan- 
tity. Introduce  the  Iron  into  a  flask  of  the  capacity  of  two  pints, 
pour  upon  it  eleven  troyounces  of  the  Muriatic  Acid  and  allow  the 
mixture  to  stand  until  effervescence  has  ceased.  Then  heat  it  to 
the  boiling  point,  decant  the  liquid  from  the  undissolved  Iron, 
filter  it  through  paper  and,  having  rinsed  the  flask  with  a  little 
boiling  distilled  water,  add  this  to  it  through  the  filter.  Pour 
the  filtered  liquor  into  a  capsule  of  the  capacity  of  four  pints, 
add  the  remainder  of  the  Muriatic  Acid,  and,  having  heated  the 
mixture  nearly  to  the  boiling  point,  add  a  troyounee  and  a  half 
of  Nitric  Acid.  When  effervescence  has  ceased  drop  in  Nitric 
Acid,  constantly  stirring,  until  it  no  longer  produces  efferves- 
cence. Lastly,  when  the  liquid  is  cold,  add  sufficient  distilled 
water  to  make  it  measure  a  pint  and  mix  it  with  the  Alcohol." 
It  will  be  observed,  that  the  Muriatic  Acid  is  here  divided 
into  two  portions,  the  second  of  which  is  added  to  the  solution  of 
the  Protochloride  of  Iron  formed  by  the  first.  This  is  done  in 
anticipation  of  the  precipitate  of  Sesquioxide  of  Iron,  which 
would  otherwise  result,  when  the  Nitric  Acid  is  added.  Here  is 
evidently  the  source  of  the  first  defect  above  alluded  to  ;  for  when 
the  mixture  is  heated  "  nearly  to  the  boiling  point"  and  the  Ni- 
tric Acid  is  added  until  effervescence  is  no  longer  produced  (as 
directed)  a  loss  of  Muriatic  Acid  will  almost  inevitably  occur, 
from  the  heat  and  the  effervescence.  Consequently  a  precipitate 
must  be  thrown  down,  from  insufficiency  of  acid.  To  remedy  the 
evil,  the  Muriatic  Acid  should  not  be  added  until  near  the  close 
of  the  operation  after  the  chemical  change,  of  the  proto- chloride 
to  that  of  sesqui-chloride  and  sesquioxide  of  Iron,  has  been  pro- 
duced by  the  Nitric  Acid,  and  the  mixture  has  nearly  cooled. 
The  sesquioxide  will  then  be  readily  dissolved,  forming  a  com- 
plete solution  of  Sesquichloride  of  Iron. 
There  are  advantages  attending  this  method,  beyond  that  of 
securing  a  reliable  tincture,  namely  :  the  more  rapid  oxidation 
of  the  Iron  by  the  Nitric  Acid,  and  the  requirement  of  smaller 
