PREPARATIONS  OF  THE  U.  S.  PHARMACOPOEIA,  1860.  381 
odor  slight  but  not  marked  ;  its  specific  gravity  is  1-350  at  60°  F., 
and  each  minim  contains  half  a  troy  grain  of  dry  citrate  of  iron. 
Ferri  Citras  results  from  the  spontaneous  evaporation  of  the 
officinal  solution  spread  on  glass,  but  its  consistence  is  too  thin  to 
retain  its  position  on  the  glass  when  spread,  and  hence  the  officinal 
direction  to  evaporate  to  a  syrupy  consistence  before  spreading. 
The  solution  soon  scales,  in  a  dry  atmosphere,  after  spreading  on 
glass.  This  form  of  citrate,  although  really  quite  soluble,  as  is 
manifest  from  its  suffering  evaporation  to  dryness  without  sepa- 
ration from  water,  yet  it  offers  considerable  resistence  to  cold 
water.  This  insolubility  is  more  apparent  than  real,  and  it  is 
overcome  at  the  ordinary  temperature  by  time,  and  much  more 
quickly  by  a  heat  of  150°  Fahr. 
Ferri  et  Ammonice  Citras. — This  formula  is  greatly  simplified, 
being  a  simple  mixture  of  solution  of  citrate  of  iron  with  aqua 
ammonia,  (U.  S.  P.) — which  neutralizes  the  acidity  of  the  solution 
— evaporated  to  a  syrup  and  spread  on  glass.  This  salt  is  much 
more  soluble  than  the  simple  citrate,  and  even  attracts  moisture 
in  a  damp  atmosphere ;  hence  it  is  called  "  soluble  citrate  of  iron." 
It  should  be  borne  in  mind  that  this  salt  will  not  do  to  make 
"  Liquor  Ferri  Citratis"  when  the  latter  is  to  be  used  for  making 
other  preparations,  as  citrate  of  iron  and  quinia,  citrate  of  iron 
and  strychnia,  etc.,  yet  under  some  circumstances,  in  the  absence 
of  the  officinal  solution,  it  maybe  justifiable  to  make  an  extempo- 
raneous solution,  making  a  slight  allowance  for  the  weight  of  the 
ammonia  present  of  about  one-ninth,  the  ammonio-citrate  being 
that  much  weaker  in  citrate  of  iron. 
Ferri  et  Quinice  Citras. — This  formula  affords  a  salt  containing 
theoretically  three  parts  of  the  alkaloid  quinia  and  twenty  parts 
of  citrate  of  iron.  Originally  the  sulphuric  acid  of  the  sulphate 
of  quinia  employed  was  replaced  by  citric  acid,  but  in  revising 
the  process  this  was  deemed  needless,  as  in  the  case  of  the  am- 
monio-citrate. Much  stress  has  been  laid  upon  the  color  of  this 
salt.  When  made  with  a  large  proportion  of  quinia,  the  scales 
have  a  greenish  cast,  and  this  is  apparent  in  the  U.  S.  Pharma- 
copoeia proportions  when  the  scales  are  thin.  The  salt  of  the 
British  Pharmacopoeia  contains  citrates  of  both  oxides  of  iron 
