PREPARATION  OF  LIQUOR  BISMUTHI.  287 
its  next  meeting ;  since,  however,  the  subject  has  been  brought 
prominently  forward  in  your  Journal,  it  will  be  more  satisfactory 
that  it  should  make  its  appearance  there.  . 
Take  of  Subcarbonate  of  Bismuth,  2  oz. 
Citric  Acid,  If  oz. 
Nitric  Acid,  3  oz. 
Water ; 
Solution  of  Potash ; 
Spirit  of  Wine, — of  each  what  is  sufficient. 
Dissolve  the  bismuth  in  the  nitric  acid,  add  sufficient  water  to 
take  up  the  nitrate  precipitated  (from  two  to  three  ounces)  • 
carefully  avoiding  excess.  Dissolve  the  citric  acid  in  the  solu- 
tion thus  formed,  (which  will  not  be  perfectly  clear,)  and  add 
gradually  solution  of  potash  (Liquor  Potassge)  until  the  mixture 
is  only  faintly  acid,  and  gives,  after  filtration,  but  a  slight  cloud 
on  the  addition  of  more  potash.  Filter,  collect  the  precipitate, 
wash  slightly,  (the  presence  of  a  trace  of  nitrate  of  ammonia  in 
the  product  is  of  no  consequence,)  and  transfer  the  precipitate 
to  a  dish ;  add  solution  of  ammonia  gradually,  until  the  precipi- 
tate is  dissolved  (a  little  oxide  will  remain);  filter.  Measure  4 
fluid  drachms  of  the  solution,  add  excess  of  sulphide  of  ammo- 
nium, collect  the  precipitate  on  a  counterpoised  filter,  wash,  dry, 
and  weigh  ;  261  grains  of  the  precipitate  thus  obtained  represent 
237  of  oxide  of  bismuth.  Dilute  the. whole  of  the  solution  with 
wTater  and  spirit  of  wine,  in  such  proportions  that  a  mixture  of 
one  part  of  spirit  with  seven  of  water  shall  contain  the  required 
number  of  grains  (I  generally  prefer  four,)  to  the  drachm  of 
solution.  In  the  above  process,  it  is  especially  necessary  to 
avoid  the  addition  of  an  excess  of  potash,  which  appears  to  de- 
compose the  citrate  formed  and  precipitate  an  oxide  insoluble  in 
ammonia,  and  this  appears  indeed  to  take  place  to  some  extent 
previously  to  saturation  ;  a  slight  waste  is  therefore  incurred, 
by  leaving  the  solution  faintly  acid,  in  order  to  avoid  the  forma- 
tion of  this  insoluble  precipitate. 
The  chief  points  in  which  I  am  indebted  to  Mr.  Bartlett,  in 
addition  to  those  mentioned  previously,  are  the  following  : — 
1.  The  substitution  of  carbonate  for  nitrate  of  bismuth.  The 
former  is  far  more  soluble  than  the  latter,  which  was  used  by  me 
in  consequence  of  its  supposed  greater  constancy  of  composition 
