^"Mar"''i88?™*}        FerHc  Citrate  and  its  Double  Salts.  117 
-citrate  with  all  the  acid  of  the  salt,  and  thus  rendering  the  iron,  as 
normal  hydrate,  seemingly  free  from  combination  with  the  acid  radicle. 
Finding  that  the  same  volume  of  dilute  ammonia  water  was  absorbed 
by  an  equivalent  of  bismuthous  citrate,  the  writer,  with  good  reason, 
•concluded  that  also  in  this  case  an  analogous  compound  resulted.  A 
recent  result  of  the  conversion  of  ferrous  into  ferric  citrate,  by  means 
•of  nitric  acid,  showed  that  the  product  was  greater  than  the  received 
formula  of  ferric  citrate  would  permit.  In  consequence  of  this  effect 
it  was  then  found  by  tlie  usual  method  of  heating  the  salt  until  the 
weight  remained  constant,  that  its  complete  formula  is  Fe  Ci  1 J  OHg. 
Treatment  with  ammonia  now  made  it  certain  that  only  two  instead  of 
three  equivalents  of  this  became  combined.  An  ammonia  water  of 
indefinite  strength  was  then  diluted  with  three  times  its  volume  of 
water  and  added  to  105  grains  of  citric  acid  until  this  was  dissolved 
and  neutralized.  The  same  dilute  ammonia  was  then  added  to  136 
grains  of  normal  ferric  citrate  in  scales  until  this  was  dissolved,  and 
an  excess  of  ammonia  appeared.  Two-thirds  as  much  was  required  as 
in  the  case  with  citric  acid.  On  evaporating  the  solution  to  dryness, 
the  scaled  salt  weighed  158  grains.    Its  formula  is,  therefore, 
Fe(NHj2Ci(OH)„  or 
Fe  =  (OH), 
I  and  molecular  weight  315. 
Ci  =  (NH,), 
Hence  it  is  a  diammonio-ferric  hydrocitrate.  The  ammonio-bis- 
muthous  hydrocitrate  is  analogously  constituted,  80  grains  of  bis- 
muthous citrate  yields  94  grains  of  the  double  salt.  Its  formula 
lience  is 
Bi  (NH,)2  Ci  (OH)2  or  Bi  =  (OH), 
I  and  its  molecular  weight  469. 
Ci  =  (NH,), 
When  one  equivalent  of  ferric  citrate  is  treated  with  not  exceeding 
two  equivalents  of  potassic  hydrate,  soluble  scaly  compounds  are  ob- 
tained. But  when  three  equivalents  of  the  alkali  is  added  a  profuse 
and  permanent  precipitate  is  formed.  136  grains  of  ferric  citrate  and 
56  grains  of  potassic  hydrate  produce  168  grains  of  the  scaled  double 
<;itrate.  Its  formula  is  therefore  Fe  K2CiO,  or 
Fe  =  0 
I  with  a  molecular  weight  of  339,  it  being  a  dipotassio  ferric 
Oi  =  K, 
oxycitrate. 
