20 
ON  TINCTURA  FERRI  CHLORIDI. 
yield  per  fluid  ounce,  130«6  grs.  sesquioxide  of  iron  by  precipi- 
tating with  ammonia  and  igniting. 
This  solution  is  the  "Liquor  Ferri  Sesqui  Chloridi,"  one  fluid 
ounce  of  which,  when  mixed  with  three  fluid  ounces  of  alcohol, 
will  form  the  Tinct.  Ferri  Chloridi  always  of  uniform  strength, 
and  containing  22-8  grains  of  iron  per  fl.  ounce.  The  Dis- 
pensatory states,  that  in  the  present  formula,  no  excess 
of  acid  exists,  and,  provided  the  digestion  is  continued  long 
enough,  no  excess  can  exist,  as  I  have  already  shown.  The 
neutral  solution,  however,  when  diluted  with  alcohol  and  ex- 
posed to  the  action  of  light  and  air,  is  liable  to  absorb  oxygen 
and  deposit  iron.  This,  perhaps,  could  be  avoided  by  adding 
a  definite  quantity  of  muriatic  acid  to  the  solution.* 
I  have  stated  that  cases  occur,  in  which  the  above  mentioned 
method  of  preparing  a  normal  solution  of  iron  can  scarcely  be 
dispensed  with  without  loss. 
I  allude  now  to  those  accidental  mishaps  which  occasionally 
are  met  with,  even  in  the  best  regulated  stores  ;  such  as  the 
tilting  over  of  the  evaporating  dish,  and  consequent  loss  of  a 
portion  of  the  acid,  or  the  solution  being  forgotten  until  nearly 
dry,  &c;  such  events  occurring,  the  loss  of  the  residue  must  fol- 
low, if  it  were  not  for  the  remedy  still  available.  In  these  and 
similar  cases,  pursue  the  same  method,  pour  olF  and  evaporate 
till  the  solution  commences  to  crystallize,  and  then  make  up  to  a 
specific  gravity  of  1-44  by  the  addition  of  water. 
In  this  proceeding,  the  employment  of  an  accurate  hydrometer 
will  facilitate  the  necessary  trials  very  much,  or,  still  better,  the 
1000  grain  bottle.  These  instruments  are  so  indispensable,  that 
every  druggist  should  be  supplied  with  them.  In  situations,  how- 
ever, where  they  cannot  be  obtained,  an  ordinary  2  oz.  vial  with 
a  narrow  neck  may  be  employed  with  advantage  for  the  same 
purpose. 
In  the  Prussian  Pharmacopoeia  there  is  an  officinal  preparation 
called  Liquor  Ferri-Sesqui  Chloridi,  made,  however,  in  a  dif- 
ferent manner  from  the  one  already  stated.    Its  advantages 
*A  slight  excess  of  acid  appears  further  desirable,  as  tending  to  the  for- 
mation of  an  ether,  which  is  thought  by  many  to  increase  the  medicinal 
efficacy  of  the  tincture. 
