212 
ON  THE  TINCTURE  OF  MURIATE  OF  IRON. 
Boil  the  hydrated  oxide  with  the  acid,  in  a  glass  or  porcelain 
vessel,  for  15  minutes,  add  the  alcohol,  and  filter.  This  tincture 
yields  35  grains  of  the  dry  oxide  to  the  fluid  ounce. 
Baltimore,  March,  1855. 
Note  by  the  Editor. — In  our  last  number  we  published  a  paper  on 
this  subject  from  Mr.  A.  P.  Sharp,  of  Baltimore,  who  suggested  that  the 
irregular,  and  too  often  deficient  strength  of  this  preparation,  was  due  to 
the  commercial  acid,  which  was  not  so  strong  as  the  officinal.  To  remedy 
this  difficulty,  he  proposed  to  pass  muriatic  acid  gas  into  the  mixture  of 
acid  and  subcarbonate  until  the  solution  is  perfect. 
Mr.  H.  W.  Fuller,  pharmaceutist,  of  Bangor,  Maine,  in  a  letter  to  the 
editor,  remarks,  in  reference  to  Mr.  Sharp's  suggestion,  "  would  it  not  be 
an  improvement  on  his  process  to  avoid  the  application  of  heat  to  the  mix- 
ture, (as  in  the  U.  S.  P.)  and  to  surround  the  solution  with  refrigerants 
while  passing  into  it  the  hydrochloric  acid  gas,"  so  as  to  favor  its  absorp- 
tion ? 
Now,  Mr.  Caldwell  aims  at  remedying  the  original  difficulty  by  the  use 
of  hydrated  sesqui-oxide  of  iron  in  the  state  of  magma,  so  as  to  effect  the 
saturation  of  the  acid  at  once.  At  first  view  this  appears  a  good  sugges- 
tion, but  on  examination  it  will  be  found  obnoxious  to  several  criticisms. 
1st.  The  magma  of  hydrated  sesqui  oxide  is  by  no  means  uniform  in  its 
state  of  hydration,  consequently,  a  given  weight  does  not  represent  a  con- 
stant quantity  of  iron.  2nd.  Muriatic  acid,  as  has  been  shown  by  Mr. 
Sharp,  cannot  be  depended  upon  for  strength,  and  as  Mr.  Caldwell's  pro- 
cess does  not  control  the  strength  of  the  acid,  this  is  another  objection. 
3d.  Admitting  that  the  quantity  of  hydrated  oxide  prescribed  should  really 
be  correct,  yet  a  deficiency  of  acid  would  still  be  able  to  dissolve  all  the 
oxide,  owing  to  the  formation  of  oxy-chloride  when  sesqui-chloride  in  solu- 
tion is  digested  with  hydrated  sesqui-oxide.  Indeed,  when  a  solution  of 
one  equivalent  of  sesqui-chloride  is  digested  till  saturated  with  the  oxide, 
the  relation  of  oxide  to  chloride  is,  according  to  Gmelin,  14Fe203+Fe2Cls. 
Further  ;  in  regard  to  Mr.  Sharp's  method,  it  may  be  proper  to  suggest 
that  it  is  liable,  in  inexperienced  hands,  to  give  an  excess  of  acid,  (and  this 
is  especially  the  case  if  Mr.  Fuller's  suggestion  is  adopted,  to  refrigerate 
the  liquid  before  passing  in  the  gas,)  as  the  solubility  of  this  gas  in  water 
is  so  great,  that  it  will  be  absorbed  more  rapidly  than  it  will  combine 
with  the  undissolved  oxide.  We  usually  overcome  the  difficulty  arising 
from  a  deficiency  in  the  strength  of  the  acid  by  adding  more  liquid  mu- 
riatic acid,  until  (with  the  application  of  a  moderate  heat)  the  solution  is 
effected.  This  plan  increases  the  proportion  of  water  slightly,  as  less  alco- 
hol is  needed  to  make  up  the  measure. 
