CITRATE  OP  IRON   AND  QUINIA.  267 
quantity  afforded  by  calculation,  and  allows  for  any  trifling 
loss. 
The  solution  should  be  kept  in  a  covered  bottle,  or  the  bottle 
should  be  kept  secluded  from  the  light,  as  this  imponderable 
agent  seems,  like  organic  matter,  to  possess  the  power  of  reduc- 
ing the  persalts  of  iron,  and  thus  the  solution  may  become  con- 
taminated with  protosulphate. 
A  solution  of  persulphate  of  iron  of  known  strength  is  very 
useful  to  the  Pharmaceutist  as  a  source  of  peroxide  in  making 
a  number  of  preparations,  and  is  also  convenient  for  the  hasty 
preparation  of  this  re-agent  when  wanted  as  an  antidote  for  ar- 
senious  acid. 
The  next  step  in  the  process  is  to  prepare  a  solution  of  am- 
monio-citrate  of  iron,  containing  an  excess  of  citric  acid,  which 
is  done  as  follows  : 
Ammonio- Citrate  of  Iron, 
Take  of  Solution  of  persulphate  of  iron,  35  fluid  ounces. 
Water  of  ammonia,  sp.  gr.  0.925  a  suflBcient  quantity. 
Citric  acid,  14J  ounces,  troy. 
Water,  a  sufficient  quantity. 
Dilute  the  solution  of  persulphate  of  iron  with  the  water  in  a 
glass  jar  or  bottle  of  proper  size,  pour  in  fifteen  fluid  ounces  of 
the  water  of  ammonia,  and  stir  the  mixture  until  the  re-action 
has  taken  place ;  allow  it  to  settle,  and  if  on  testing  the  clear 
solution  it  is  found  to  contain  no  iron,  w^ash  the  precipitate  in 
the  usual  manner,  until  the  washings  are  tasteless.  Should  the 
supernatent  liquid  contain  iron,  more  ammonia  is  necessary,  be- 
fore proceeding  with  the  washing.  The  precipitate  is  now  to  be 
transferred  to  a  muslin  filter  and  allowed  to  drain  until  it  as- 
sumes the  form  of  a  magma,  when  it  should  be  placed  in  a  dis^ 
with  the  citric  acid,  and  the  mixture  heated  by  means  of  a  water- 
bath  until  the  peroxide  is  perfectly  dissolved  ;  then  add  six  fluid 
ounces  of  the  water  of  ammonia,  remove  the  dish  from  the 
water-bath  and  allow  the  solution  to  cool. 
Having  now  obtained  a  clear  solution  of  ammonio-percitrate 
of  iron,  containing  an  excess  of  citric  acid,  the  next  step  is  to 
introduce  the  quinia,  for  which  purpose  carbonate  of  quinia  is 
prepared  as  follows : 
