Am.  Jour.  Pharm. 
Jan.,  1887. 
Bismuth  Subiodide. 
13 
Concerning  the  present  chemical  formula  given  to  subnitrate  of 
bismuth  by  our  present  pharmacopoeial  standard  (U.  S.  P.  1880), 
there  is  much  to  be  said  in  criticism  upon  it.  The  Pharm.  Germ.1 
says  of  this  bismuth  salt,  that  "  when  heated  to  120°C.  (248°F.)  it  loses 
between  3  and  5  per  cent,  of  moisture,  and  at  a  red  heat  gives  off 
yellowish-red  vapors,  and  leaves  between  79  and  82  per  cent,  of  bis- 
muthous  oxide." 
In  confirmation  of  this  view,  Mr.  S.  E.  Wolf 2  has  made  a  series  of 
quantitative  experiments,  as  follows,  (using  30  gm.  of  bismuth  subni- 
trate, dissolved  in  30  cc.  of  nitric  acid,  with  the  aid  of  heat,  and  dilu- 
ting with  sufficient  distilled  water  to  make  150  cc.) ;  10  cc.  of  the 
solution  were  precipitated,  first  with  50  cc.  cold  water,  secondly  with 
50  cc.  boiling  water,  and,  thirdly,  with  500  cc.  cold  water ;  the  pre- 
cipitates were  dried  in  an  air-bath,  weighed,  then  ignited  and  again 
weighed.  A  sample  of  bismuth  subnitrate  (iv.),  prepared  strictly  in 
accordance  with  the  U.  S.  P.  (1870),  formula  was  examined,  in  like 
manner.    The  results  are  as  follows  : 
I.  II.  III.  IV. 
"Weight  of  precip.,      10  gm.  r05  gm.  '396  gm.  1*0  gm. 
Weight  of  oxide,      753  gm.  '855  gm,  "329  gm.  '865  gm. 
Percentage  of  oxide,  753  81*4  83*3  86*5 
In  corroboration  of  these  statements  we  have  just  given,  in  this 
month's  Jouknal,3  the  results  of  Mr.  S.  L.  Kambo,  who  found,  in 
drying  four  samples  of  the  commercial  salt,  at  120°C,  that  the  loss  in 
weight,  from  the  evaporation  of  moisture,  varied  between  2'0  and  3*42 
per  cent.,  and  the  oxide,  resulting  from  ignition,  weighed  79*2,  79*8, 
80*2  and  80*25  per  cent. ;  results  agreeing  fairly  with  those  above. 
Now  the  formula  BiO  NOa  indicates  81*2  per  cent.  Bi2Os,  and  the 
formula  BiO  N03.H20,  (U.  S.  P.  '80)  equals  76*47  per  cent,  oxide, 
whereas  the  general  results  of  Messrs.  Wolf  and  Rambo  plainly  point 
to  the  first  formula,  and  from  these  data  it  may  safely  be  concluded 
that  the  varying  quantities  of  moisture  contained  in  commercial  bis- 
muth subnitrate  is  dependent,  first,  upon  the  relative  quantity  of 
water  used  to  precipitate  the  oxysalt,  and,  secondly,  upon  the  relative 
degree  and  duration  of  heat,  with  which  the  oxysalt  is  dried,  and,  that 
the  contained  water  from  its  variations  in  quantities  is  not  water  of 
1  P.  G.  vide  Nat.  Dispensatory,  3d  Edt,  p.  322. 
2  Amer.  Jour.  Pharm..  Dec,  1882,  p.  593-595. 
3  Bis.  Sub.  Nit.  Amer.  Jour.  Pharm.,  Dec,  1886,  p.  592. 
