348 
A  NEW  BELLADONNA  PLASTER. 
much  lighter  than  the  tincture  without  ammonia ;  the  interme- 
diate numbers  were  also  intermediate  in  color.  For  complete 
decoloration,  No.  4  required  6  days  ;  No.  3,  9  days  ;  No.  2,  27 
days  ;  No.  1,  35  days.  The  proportions  of  No.  1,  therefore, 
would  be  least  objectionable  on  account  of  its  small  quantity  of 
ammonia,  though  requiring  rather  a  long  time  for  decoloration. 
A  modification  of  this  process  for  a  speedy  preparation  of 
colorless  tincture  of  iodine  without  excess  of  ammonia  has  sug- 
gested itself  to  me,  and  upon  trial  given  satisfactory  results, 
though  I  would  only  recommend  it  in  cases  where  the  shortness 
of  time  forbids  the  employment  of  the  other.  This  consists  in 
speedily  decolorizing  the  solution  of  iodine  in  alcohol  by  a  sur- 
plus of  ammonia,  and,  after  decoloration,  carefully  adding  hy- 
drochloric acid  until  the  reaction  remains  but  feebly  alkaline. 
The  hydrochloric  acid  forms  with  the  free  ammonia  chloride  of 
ammonium,  which,  being  but  slightly  soluble  in  alcohol,  is  nearly 
all  precipitated  in  the  form  of  a  white  crystalline  powder,  while 
the  iodide  of  ammonium  and  iodate  of  ammonia  remain  in  solu- 
tion. An  addition  of  even  a  slight  excess  of  acid  would  destroy 
the  preparation,  restoring  the  color  of  the  tincture,  by  decom- 
posing the  ammonia  compounds  of  iodine  ;  the  precipitate  can 
be  readily  removed  by  filtration.  Very  strong  alcohol  should 
be  employed  in  this  process,  as  the  completeness  of  the  precipi- 
tation of  chloride  of  ammonium  is  in  direct  proportion  to  the 
strength  of  the  alcohol.  As  some  of  the  chloride  of  ammonium, 
however,  remains  in  all  cases,  and  more  material  is  required  to 
accomplish  the  same  object,  I  should  give  the  simpler  process 
of  slow  decoloration  by  addition  of  a  minimum  of  ammonia  the 
preference. — St.  Louis  Medical  Reporter^  June  Is^,  1869. 
A  NEW  BELLADONNA  PLASTER. 
To  tlie  Editor  of  the  Pharmaceutical  Journal : 
Gentlemen, — Your  correspondent,  Mr.  Gissing,  in  the  last 
number,  asks  for  certain  information  relative  to  the  extract  of 
belladonna  now  in  use  for  making  the  emplastrum  belladonnas 
of  the  British  Pharmacopoeia,  which  I  am  not  able  to  give  ;  but, 
as  belladonna  plaster  has  for  some  time  occupied  my  attention, 
