262 
LIQUOR  BISMUTHI  ET  AMMONUE  CITRATIS. 
rified  as  the  Pharmacopoeia  directs,  I  failed  to  detect  either  cop- 
per, arsenic,  or  antimonj.  In  no  case  could  I  find  the  last  two 
metals,  but  in  one  case  I  obtained  a  trace  of  copper.  The  liquor 
which  contained  it,  however,  was  prepared  from  metal  imperfect- 
ly purified,  for  the  fusion  with  nitre  was  not  carried  on  sufficient- 
ly. It  is  to  be  observed  that  the  Pharmacopoeia  directs  the  com- 
mercial bismuth  to  be  twice  fused  with  nitre,  stirring  the  molten 
mixture  for  a  quarter  of  an  hour  each  time.  Copper  is  the  most 
abundant  impurity  of  bismuth,  and  would  most  readily  pass  into 
the  liquor  prepared  from  metal  containing  it.  When  ordinary 
commercial  bismuth  is  employed  for  the  preparation  of  the  liquor 
in  place  of  the  purified  bismuth  ordered,  the  resulting  solution 
does  undoubtedly  contain  copper,  and  may  contain  traces  of  ar- 
senic and  antimony;  although  the  latter  is  mostly  deposited  from 
the  nitric  acid  solution  as  insoluble  antimonic  acid,  together  with 
at  least  part  of  the  arsenic  as  arseniate  of  bismuth. 
Judging  from  the  experiments  I  have  made,  I  think  it  is  safe 
to  conclude  that  w*hen  the  Pharmacopoeia  instructions  are  proper- 
ly carried  out,  the  process  yields  with  the  greatest  facility  a  so- 
lution of  ammonio-citrate  of  bismuth  which  is  associated  only 
with  nitrate  of  ammonia,  and  is  in  other  respects  pure  and  trust- 
worthy. But  the  substitution  of  commercial  for  purified  bismuth 
would  be  an  improper  departure  from  the  directions  of  the  Phar- 
macopoeia, and  would  be  likely  to  cause  the  introduction  of  ob- 
jectionable impurities  into  the  preparation.  The  purification  of 
the  metal  is  an  important  part  of  the  process. 
Although  the  Pharmacopoeia  process  is  a  very  satisfactory  one, 
I  have  found  it  advantageous,  in  manufacturing  this  liquor,  to 
depart  from  the  letter  of  the  instructions,  and  to  employ,  in  the 
place  of  metallic  bismuth  and  nitric  acid,  the  crystallized  terni- 
trate  of  bismuth,  as  proposed  by  Mr.  Tichborne  some  years  back. 
This  modification  of  the  Pharmacopoeia  process,  while  it  is  in 
some  respects  more  ready  and  convenient,  happens  to  afford 
greater  security  "for  the  purity  of  the  product.  It  has  the  addi- 
tional advantage  also  of  introducing  a  minimum  and  uniform 
quantity  of  nitrate  of  ammonia  into  the  resulting  liquor.  The 
crystallized  nitrate  is  readily  obtained  and  easily  kept.  When 
bismuth  is  dissolved  in  nitric  acid,  the  solution,  after  concentra- 
