TINCTURA  FERRI  CHLORIDI. 
459 
nate  of  iron  in  one  pint  of  muriatic  acid,  and  adding  the  solution 
to  three  pints  of  alcohol.  It  seems  to  have  been  a  constant  source 
of  annoyance.  The  formula  was  evidently  based  on  the  use  of  the 
officinal  sub-carbonate  of  iron,  recently  precipitated,  in  which 
state  six  troyounces  would  readily  enough  dissolve  in  a  pint  of 
muriatic  acid.  When,  however,  the  sub-carbonate  had  been  kept 
some  time,  and  had  become  more  or  less  completely  converted 
into  hydrated  oxide,  then  the  six  troyounces  would  contain  a 
much  larger  proportion  of  iron,  and  would,  consequently,  require 
a  larger  quantity  of  acid  for  solution.  The  formula  made  no 
provision  for  this  change  in  the  sub-carbonate,  hence  the  whole 
trouble. 
As  an  officinal  process,  however,  for  the  preparation  of  Tine, 
ferri  chloridi,  the  experience  of  the  writer  leads  him  to  regard 
the  method  of  obtaining  the  necessary  sesqui-chloride  by  the 
direct  solution  of  sub-carbonate,  or  rather  hydrated  oxide,  in 
muriatic  acid,  as,  on  the  whole,  preferable  to  that  at  present 
sanctioned  by  the  Pharmacopoeia. 
The  writer  finds  no  difficulty  in  obtaining  commercial  sub-car- 
bonate of  iron  that  is  perfectly  soluble  in  the  proper  amount  of 
muriatic  acid,  and  sufficiently  uniform  in  composition  for  all 
practical  purposes.  The  following  three  samples  will  illustrate 
the  various  grades  met  with  by  the  writer,  and  are  believed  to 
be  a  fair  representation  of  the  commercial  character  of  this 
article  : 
No.  1.  100  grs.  exposed  to  a  red  heat  for  half  an  hour, 
yielded  85  grs.  sesquioxide,  and  was  of  a  dark,  reddish-brown 
color. 
No.  2.  100  grs.  ignited  in  the  same  way,  yielded  83  grs. 
sesqui-oxide.    Color  w^as  lighter  than  preceding. 
No.  3.  100  grs.  ignited  in  the  same  way,  yielded  80  grs. 
sesqui-oxide,  and  was  a  shade  lighter  in  color  than  No.  2. 
An  article  labelled  ^' Ferri  Proto.-Carb.  (?)  Precip.,"  and  put 
up  in  bottles,  is  also  met  with.  It  contains  a  large  proportion 
of  proto-carbonate,  and  is  well  adapted,  doubtless  to  therapeutic 
administration.-  In  the  preparation  of  tincture,  however,  its  use 
is  not  attended  with  any  advantage,  and  being  more  expensive, 
it  is  here  left  out  of  consideration,  reference  being  had  only  to 
