NEW  ADULTERATION  OF  SUBNITRATE  OF  BISMUTH.  407 
chloride.  This  is  so  frequently  met  with  in  commercial  subnitrate 
of  bismuth  that  its  detection  would  not  have  excited  much  sur- 
prise. Its  presence  is  excused  by  manufacturers  on  the  ground 
of  its  making  the  powder  more  suitable  for  some  of  the  purposes 
to  which  it  is  applied,  so  that  for  such  purposes  the  powder  would 
be  unsaleable  if  it  did  not  contain  any  chloride.  The  chlorine 
having  been  estimated,  and  the  equivalent  quantity  of  oxychloride 
calculated  therefrom,  a  further  examination  rendered  it  evident 
that  there  was  something  else  present  besides  subnitrate  of  bis- 
muth. The  residue  left,  after  calcination,  was  in  excess  of  that 
which  theory  indicated  ;  and  this  residue  dissolved  in  nitric  acid, 
mixed  with  dilute  acetic  acid,  and  precipitated  with  sulphuretted 
hydrogen,  gave  an  amount  of  sulphide  much  below  the  theoreti- 
cal quantity.  The  cause  of  these  discrepancies  was  found  in 
the  filtiate,  which  yielded  an  abundant  precipitate  of  phosphate 
of  lime. 
While  I  was  engaged  in  this  investigation,  my  attention  was 
directed  to  a  paper  in  the  "  Journal  de  Pharmacie  et  de  Chimie" 
for  last  March,  by  Mr.  Roussin,  in  which  he  alludes  to  the  adul- 
teration of  subnitrate  of  bismuth  with  phosphate  of  lime,  and 
describes  a  very  simple  method  of  detecting  it.  Mr.  Roussin 
says  that  in  one  case  he  found  as  much  as  28  per  cent,  of  phos- 
phate of  lime  in  a  sample  which  presented  the  usual  appearance, 
and  answered  to  the  ordinary  tests  of  subnitrate  of  bismuth.  His 
process  for  its  detection  and  estimation  is  as  follows :  Dissolve 
equal  quantities  of  the  subnitrate  and  of  tartaric  acid  in  nitric 
acid  slightly  diluted  with  water,  and  add  to  this  a  strong  solution 
of  carbonate  of  potash  until  all  effervescence  has  ceased,  and  the 
liquid  is  rendered  strongly  alkaline.  "  If  the  subnitrate  of  bis- 
muth be  pure  the  liquid  will  be  clear,  and  will  remain  so  even 
after  it  has  been  boiled  ;  but  if  the  sample  of  subnitrate  submitted 
to  the  test  should  contain  phosphate  of  lime,  even  to  the  extent 
of  1  or  2  per  cent.,  this  will  form  a  white  precipitate,  which  will 
not  dissolve  with  long-continued  boiling." 
In  applying  this  test,  it  is  important  to  observe  that  the  phos- 
phate of  lime,  even  when  present  in  large  quantity,  is  not  pre- 
cipitated in  the  first  instance  after  the  addition  of  the  carbonate 
of  potash,  but  its  precipitation  is  immediately  effected  by  boiling 
