162 
ADMINISTRATION  OF  BISMUTH. 
analogous  to  3MOCi  +  MO  ;  one  of  the  bases,  MO,  being  re- 
placed by  Bi03 :  it  is  made  from  the  recently  precipitated  and 
well-washed  oxide.  From  the  peculiarity  of  having  to  deal  with 
an  alkaline  bismuthic  solution,  direct  precipitation  with  sul- 
phide of  ammonium  was  employed  to  determine  the  amount  of 
bismuth  present ;  this  gave,  on  washing  and  drying,  0-327 
grammes  of  BiS3  in  the  fluid  half-ounce,  which  represents  1*114 
grains  of  the  teroxide  as  being  present  in  the  drachm.  Now, 
although  the  circular  which  accompanies  the  Liq.  Bismuthi 
states  that  ^j.  is  equivalent  to  a  full  dose  (fifteen  to  twenty 
grains)  of  the  insoluble  trisnitrate,  I  do  not  think  that  such  can 
be  the  case.  The  idea  evidently  is  that  the  metal,  when  in  the 
soluble  form,  is  much  more  active  than  the  ordinary  insoluble 
modification,  and  there  can  be  no  doubt  that  it  is  so  to  a  cer- 
tain extent ;  but  I  should  consider  three  grains  to  the  drachm 
as  the  minimum  dose  :  even  more  than  this  quantity  may  be  easily 
introduced  into  such  a  solution  as  the  above.  The  following  is 
probably  the  mode  pursued  in  making  this  solution  : — 430 
grains  of  metallic  bismuth  are  dissolved  in  a  sufficient  quantity 
of  nitric  acid,  and  this  solution  of  ternitrate  of  bismuth  is  then 
precipitated  with  ammonia,  and  the  resulting  hydrated  oxide 
well  washed  ;  480  grains  of  citric  acid  are  then  exactly  neutral- 
ized with  ammonia,  and  the  moist  oxide  is  gradually  added  to 
the  boiling  solution  of  citrate  of  ammonia.  The  oxide  is  slowly 
but  perfectly  taken  up.  Ammonia  is  slightly  evolved  during 
the  boiling,  (probably  from  the  decomposition  of  the  citrate  of 
ammonia  per  se,}  but  the  solution  becomes  slightly  acid,  and 
remains  so  until  the  completion  of  the  process.  The  solution  is 
then  neutralized  with  ammonia,  and  the  whole  is  made  to  mea- 
sure one  pint.  This  solution  will  contain  three  grains  of  Bi03 
to  the  53.  It  is  more  elegantly  made  by  dissolving  the  citrate 
of  bismuth  in  citrate  of  ammonia.* 
Tartaric  acid  has  also  a  similar  action  upon  bismuth. 
There  seems  to  be  a  limit  to  the  solubility  of  chemically  pure 
citrate  of  bismuth ;  but  the  solubility  is  wonderfully  increased 
*  Citrate  of  bismuth  is  a  very  insoluble  salt,  got  by  the  double  decompo- 
sition of  titrate  of  potash  or  soda,  and  ternitrate  of  bismuth.  The  citrate, 
as  made  in  this  manner,  is  extremely  soluble  in  ammonia,  or  a  solution  of 
ciirate  of  ammonia. 
