328      PREPARATIONS  OP  THE  U.  S.  PHARMACOPOEIA,  1860. 
ounces  of  powdered  sugar.  As  this  change  does  not  affect  the 
integrity  of  the  preparation,  and  renders  the  pills  much  less 
prone  to  soften,  it  is  a  justifiable  deviation  from  the  officinal 
rule. 
Liquor  Ferri  Nitratis. — In  this  formula  the  nitric  acid  is  added 
to  the  iron  in  excess,  so  as  to  get  nitrate  of  the  protoxide.-  In 
the  previous  edition,  the  iron  was  added  to  the  acid  in  excess 
until  the  latter  was  saturated,  avoiding  the  full  oxidation  of  the 
iron  by  controlling  the  temperature,  a  mixture  of  nitrates  result- 
ing. The  latter  was  found  to  be  ineligible,  and,  in  the  same 
hands,  to  afford  variable  results.  The  former  yields  a  constant 
preparation  when  the  reaction  is  properly  controlled  so  as  to 
avoid  the  formation  of  nitrous  vapors  in  the  solution  of  the  iron. 
For  further  reasons,  consult  the  original  paper,  Amer.  Journ. 
Pharm.,  July,  1857,  p.  306. 
Liquor  Ferri  Tersulphatis. — So  much  has  been  written  and 
printed  in  this  Journal  relative  to  this  solution,  (see  vols.  xxv.  and 
xxxii.)  that  but  a  short  reference  is  required  in  this  notice.  Instead 
of  giving  the  ingredients  and  process  for  the  tersulphate  under  each 
formula  requiring  its  use,  as  in  previous  editions,  a  distinct 
formula  has  been  given  for  the  solution.  The  only  caution  that 
occurs  to  mention  is  one  that  applies  to  the  inexperienced  or 
careless.  It  will  be  observed  that  a  fixed  quantity  of  nitric  acid 
is  directed.  If,  as  is  very  frequently  true,  the  nitric  acid  is 
weaker  than  sp.  gr.  1.42,  there  will  be  insufficient  to  peroxidize 
all  the  iron,  and,  as  a  consequence,  the  solution  will  contain 
some  protoxide,  which  will  cause  a  greater  or  less  tendency  to 
blackness  in  the  color  of  the  oxide  it  affords  on  the  addition  of 
ammonia.  Now  an  expert,  knowing  the  necessity  of  the  full 
complement  of  acid,  would  increase  the  quantity,  or  continue  to 
add  it  afterwards,  until  ardrop  caused  no  effervescence.  The 
novice  should  therefore  assure  himself  that  all  is  right  by  testing 
a  few  drops,  diluted  with  water,  by  adding  an  excess  of  ammonia, 
and  if,  instead  of  a  reddish-brown  precipitate,  it  affords  one  of  a 
bluish-black  or  blackish-brown  color,  he  should  then  add  more 
nitric  acid,  as  stated  above. 
Liquor  Ferri  Subsulphatis.    MonseVs  Solution. — It  is  unfor- 
