PHOSPHATE  OF  LIME  IN  SUBNITRATB  OF  BISMUTH.  129 
ON  THE  DETECTION  OF  PHOSPHATE  OF  LIME  IN  SUB- 
NITRATE  OF  BISMUTH. 
By  Mr.  G.  G.  Hornsby. 
I  was  not  in  time  for  the  September  issue  of  the  Journal,  or  I 
should  have  sent  some  remarks  on  the  ^'  Note  on  a  New  Adultera- 
tion of  Subnitrate  of  Bismuth,"  by  Dr.  Redwood.  I  am  glad, 
however,  to  find  that  Messrs.  Howard  and  Sons  have  pointed 
out  (what  I  had  previously  proved  by  careful  experiment)  that 
this  test,  suggested  by  Mr.  Roussin  and  supplemented  by  Dr. 
Redwoodj  for  the  detection  of  phosphate  of  lime,  was  fallacious. 
This  point  established,  I  have  somewhat  to  say  upon  the  modifi- 
cation suggested  by  Messrs.  Howard  and  Son. 
The  process  they  suggest  possesses  some  advantages  over  that 
of  Mr.  Roussin,  but  cannot,  ]per  se,  be  relied  upon,  as  the  follow- 
ing results  will  show.  I  have  operated  upon  several  samples  as 
follows  : — 
1st.  One  part  of  the  salt  of  bismuth,  dissolved  in  nitric  acid 
moderately  dilute,  two  parts  citric  acid,  dissolved  in  a  little 
water ;  then  add  an  excess  of  ammonia,  and  boil.  This  solution 
remains  perfectly  clear  until  it  is  boiled,  but  when  it  reaches  the 
boiling-point  it  lets  fall  a  bulky  basic  precipitate,  which  remains 
insoluble  until  the  solution  has  been  boiled  for  some  minutes 
longer  ;  it  then  parts  with  its  ammonia,  assumes  a  slightly  acid 
condition,  when  the  precipitate  redissolves  and  remains  perfectly 
bright. 
2d.  Proceeded  as  above,  adding  two  grains  of  phosphate  of 
lime  to  the  bismuth  salt  previous  to  solution.  The  result  was 
similar  to  the  above,  with  this  exception :  the  precipitate  redis- 
solved,  but  left  the  solution  somewhat  opalescent,  and,  after  the 
lapse  of  twelve  or  fourteen  hours,  gave  an  abundant,  insoluble 
basic  precipitate.  Not  satisfied  with  the  result  of  these  experi- 
ments, I  adopted  the  same  method  again  with  two  more  samples, 
this  time  omitting  the  boiling  altogether. 
1st.  As  No.  1  before  named,  not  boiled. 
2d.  As  No.  2 ;  two  grains  phosphate  of  lime  added  ;  not 
boiled.  The  first  solution  remained  perfectly  clear,  and  has 
done  so  for  many  days.    The  second,  after  the  lapse  of  five  or 
9 
