PREPARATION  OF  IODIDE  OF  AMMONIUM.  21 
Cantharides,  in  a  very  fine  powder,  64  grains,  or  what  would  be 
sufficiently  accurate,  4  troy  ounces  of  the  first  and  50J  grains  or 
50  grains  of  the  other. 
I  present  some  samples. 
No.  1,  is  made  by  the  officinal  formula,  using  true  Burgundy 
pitch. 
No.  2,  is  made  by  the  formula  proposed  as  a  substitute  for  the 
other,  but  using  the  American  imitation  of  the  pitch. 
No.  3,  by  the  proposed  formula,  using  true  Burgundy  pitch. 
No.  1,  I  find  is  softer  than  the  others  at  a  temperature  of  70° 
and  over,  but  cracks  more  readily  when  reduced  to  60°.  I  per- 
ceive no  difference  between  No.  2  and  No.  3  in  consistence,  the 
American  Burgundy  Pitch  appearing  to  answer  equally  as  well 
as  the  true. 
The  better  consistence  of  the  plaster  made  by  the  proposed 
formula  I  attribute  partly  to  its  containing  more  wax  than  the 
officinal,  the  wax  being  but  slightly  effected  by  the  temperature 
until  it  nearly  reaches  its  melting  point. 
This  also  prevents  its  cracking  when  exposed  to  the  cold,  which 
I  think  is  of  some  importance,  though  not  embraced  in  the  ques- 
tion.— Proc.  Am.  Pharm.  Assoc,  1866. 
NOTE  ON  THE  PREPARATION  OF  IODIDE  OF  AMMONIUM. 
By  James  F.  Babcock. 
Having  occasion  some  time  since  to  prepare  this  salt  in  con- 
siderable quantities,  my  experience  with  the  various  processes 
laid  down  in  the  books  may  not  be  uninteresting. 
The  first  process  tried  was  that  of  Spencer,  ( IT.  S.  Dispensa- 
tory, 12  Edition,  p.  1537),  which  consists  of  adding  hydro- 
sulphuret  of  ammonia  to  iodine  until  the  red  color  due  to  the 
solution  of  iodine  in  iodide  of  ammonium  has  disappeared. 
Iodine  displaces  the  sulphur,  and  the  liquid  filtered  to  separate 
the  deposited  sulphur  is  evaporated  to  dryness. 
The  deportment  of  the  iodide  of  ammonium  thus  formed 
showed  that  the  decomposition  of  the  hydrosulphuret  involved 
the  formation  of  certain  combinations  with  sulphur,  traces  of 
which  obstinately  adhered  to  the  iodide  of  ammonium  produced, 
and  in  time,  even  when  excluded  from  light,  its  color  changed  to 
