PHOSPHATE  OF  LIME  IN  SUBNITRATE  OF  BISMUTH.  543 
No.  1  contains  some  of  the  kind  I  find  best ;  it  is  imported  in 
roundish  blocks,  which  are  exceedingly  hard  and  difficult  to  cut, 
but  any  of  the  large  gutta  percha  manufacturers  will  supply  the 
same  torn  into  fragments  similar  to  the  accompanying  specimen. 
Four  ounces  of  this  digested  with  five  pounds  of  methylated 
chloroform  for  a  few  days,  will  form  a  solution  sufficiently  fluid 
to  filter  through  ordinary  bibulous  paper ;  this  should  be  con- 
ducted in  such  a  manner  as  to  allow  little  or  no  loss  of  chloro- 
form by  evaporation,  the  apparatus  for  filtering  volatile  liquids 
described  in  Mohr  and  Redwood's  "  Pharmacy  "  answering  the 
purpose  ;  the  addition  of  another  pound  of  chloroform  rendering 
the  filtration  more  expeditious.  To  the  filtered  solution,  which 
should  be  bright  and  nearly  colorless,  add  an  equal  bulk,  or  a 
sufficient  quantity  of  spirit  of  wine  to  precipitate  the  gutta  per- 
cha, which  will  separate  from  its  solvent  as  a  white  bulky  mass  ; 
this  should  be  rinsed  with  spirit,  pressed  in  a  cloth,  and  dried 
by  exposure  to  the  air  ;  its  condition  is  then  that  of  the  accom- 
panying specimen,  marked  "No.  2,"  perfectly  white,  but  too 
porous  for  dental  use  ;  it  should  then  be  boiled  for  half  an  hour 
in  a  porcelain  capsule  and  rolled  in  sticks  whilst  hot,  as  specimen 
"  No.  3."  The  chloroform  can  now  be  separated  from  the  spirit 
by  the  addition  of  water,  and  lastly  the  spirit  from  the  water  by 
distillation,  at  the  leisure  of  the  operator. 
There  is,  therefore,  no  reason  why  the  chemist  should  not  pre- 
pare this  substance  himself,  and  if  he  is  careful  to  prevent  the 
loss  of  chloroform  and  spirit  in  the  process,  its  reduced  cost  and 
greater  purity  will  compensate  him  for  the  trouble. — -London 
Pharm.  Journ.,  Sept.,  1868. 
NOTE  ON  THE  DETECTION  OF  PHOSPHATE  OF  LIME  IN 
SUBNITRATE  OF  BISMUTH. 
By  Dr.  Redwood. 
In  a  brief  notice  1  gave,  in  the  last  number  of  this  Journal,  of 
the  adulteration  of  subnitrate  of  bismuth  with  phosphate  of  lime, 
I  alluded  to  a  test  recently  published  by  Mr.  Roussin.  I  am 
informed  by  Messrs.  Howard  and  Sons,  of  Stratford,  that  they 
have  found  this  test  fallacious,  as  continued  boiling  causes  a  pre- 
