Am.  Jour.  Pharm  \ 
Mar,  1879  J 
Bismuthi  Subnitras. 
143 
THE  INCOMPATIBILITY  OF   BISMUTHI  SUBNITRAS 
WITH  THE  ALKALINE  BICARBONATES. 
By  Thomas  Green. 
Although  this  subject  has,  both  recently  and  on  a  former  occasion, 
attracted  much  attention  and  comment,  it  can  scarcely  be  said  that  it 
has  been  satisfactorily  settled,  inasmuch  as  opinion  seems  divided  as  to 
whether  the  evolution  of  C02  from  the  alkaline  bicarbonates  is  due  to 
free  acid  in  the  bismuth  subnitrate,  or  to  the  chemical  action  which 
the  latter  has  on  the  former;  the  preponderance  of  opinion  inclining 
to  the  former  theory.  Mr.  Yeats,  who,  I  believe,  first  drew  attention 
to  the  subject,  tested  the  bismuth  he  had  used  and  finding  it  to  be 
slightly  acid,  thought  that  might  account  for  the  explosion,  but,  how- 
ever, added  that  the  real  cause  was  probably  a  decomposition  between 
the  two  salts,  and  formed  an  equation  representing  such  decomposition. 
The  following  rough  experiments  seem  to  bear  out  the  latter 
assumption,  which  also  accords  with  the  opinion  of  Squire,  who  gives 
as  incompatibles  of  bismuth  subnitrate  the  alkalies  and  alkaline 
carbonates. 
Two  drachms  of  bismuth  subnitrate  and  the  same  of  sodium  bicar- 
bonate were  mixed  with  a  small  quantity  of  distilled  water,  and  the 
bottle  containing  them  was  corked  and  set  aside.    In  a  short  time, 
perhaps  ten  minutes,  effervescence  commenced  and  in  about  an  hour 
the  cork  was  expelled  from  the  bottle.    The  cork  was  replaced  and 
the  reaction  allowed  to  go  on  until  all  effervescence  had  ceased.  The 
mixture  was  then  transferred  to  a  small  filter,  and  the  filtrate  tested 
for  HNO3,  which  was  found.    The  precipitate,  after  being  very  well 
washed,  was  also  examined  for  HNOs,  but  without  success.    It,  how- 
ever, effervesced  briskly  on  the  addition  of  dilute  sulphuric  acid,  prov- 
ing the  presence  of  C02.     Examined  by  a  lens,  the  precipitate  had 
'lost  the  crystalline  structure  of  the  subnitrate,  corresponding  now  in 
appearance  with  the  carbonate.    This  experiment  was  repeated,  sub- 
stituting sodium  carbonate  for  the  bicarbonate,  with  the  following 
result:    No  effervescence  whatever  took  place,  but  at  the  end  of  forty- 
eight  hours  the  bismuth  was  examined  and  found  to  be  entirely  con- 
verted into  the  carbonate. 
I  need  not  add  that  the  bismuth  subnitrate  was  perfectly  neutral  in 
its  action  on  litmus  paper,  as  the  latter  experiment  fully  proves. 
