388 
Tinctura  Ferri  Chloridi. 
(  Am.  Jour,  Pharm. 
\    August,  1883. 
In  preparing  the  Liquor  ferri  chloridi,  according  to  the  formula  of 
the  U.  S.  Pharmacopoeia  of  1880,  the  mixture  of  iron,  acid,  and  water 
is  to  be  raised  to  the  boiling  point  after  the  cold  mixture  has  ceased  to 
effervesce.  If  the  mixture  be  boiled  at  this  point,  a  large  quantity  of 
the  acid  will  be  driven  off  and  thus  lost ;  and  if  the  solution  be  fil- 
tered at  the  time  directed,  only  about  one-third  of  the  acid  will  be 
neutralized.  Much  better  results  are  obtained  by  a  gentle  heat  applied 
for  several  hours,  until  effervescence  again  ceases,  when  the  solution 
should  be  raised  to  the  boiling  point  and  filtered.  After  careful  man- 
ipulation, using  pure  acids  of  the  proper  strength,  the  solution  was 
found  to  have  the  specific  gravity  1*390,  and  this  was  the  highest  that 
could  be  obtained  by  following  the  directions  of  the  Pharmacopoeia, 
which  requires  a  density  of  1*405. 
On  investigating  the  cause  of  this,  it  was  observed  that  the  admix- 
ture Avith  nitric  acid  was  to  be  performed  in  a  capacious  porcelain  ves- 
sel. If  so  mixed,  a  considerable  quantity  is  lost  by  the  energy  of  the 
reaction,  and  the  loss  materially  reduces  the  specific  gravity  of  the 
resulting  solution.  It  is  probable  that  the  experiments  incident  to  the 
construction  of  this  formula  were  made  in  a  flask,  which  would  pre- 
vent the  loss  of  any  portion  of  the  liquid. 
If  this  conclusion  be  correct,  the  specific  gravity  of  the  officinal 
solution  is  certainly  wrong.  On  inquiry  among  pharmacists,  it  was 
found  that  the  same  trouble  had  been  experienced  by  others. 
The  Pharmacop(]eia  states  that  10  grams  of  the  solution,  when  com- 
pletely precipitated  by  ammonia  (NH^OH),  yields  a  precipitate  which, 
when  washed,  dried,  and  ignited,  should  weigh  1*86  grams.  These 
directions  having  been  followed  precisely,  with  a  solution  of  less  spe- 
cific gravity  (1*390)  than  the  officinal,  the  residue  weighed  1*882  gm. 
With  the  solution  sp.  gr.  1*390,  the  tincture  was  then  made  according 
to  the  officinal  formula.  The  specific  gravity  was  '965,  while  the  offi- 
cinal is  stated  to  be  about  '980. 
Ten  specimens  of  Tinct.  ferri  chloridi,  U.  S.  P.,  1880,  were  obtained 
from  leading  pharmacists  of  Philadelphia.  These  answered  to  the 
tests  for  purity,  but  the  specific  gravities  of  all  were  found  to  vary 
between  '950  and  '970,  except  one,  w^hich  was  1*005,  and  which 
proved  to  have  been  made  with  diluted  alcohol  instead  of  alcohol  sp. 
gr.  -820. 
To  ascertain  the  amount  of  iron  present  in  each,  a  solution  of  potas- 
sium permanganate  was  made,  3*14  gm.  K2Mn208,  being  dissolved  in 
