846 
HYDRIODATE  OF  AMMONIA. 
Any  inert  coloring  matter  may  be  added  to  please  the  fancy 
of  the  operator. 
Each  fluid  drachm  contains  two  grains  of  the  salt. 
Curacoa  cordial  is  frequently  used  in  disguising  the  disagree- 
ble  taste,  not  only  of  Valer.  Ammon.,  but  other  pharmaceutical 
preparations. — Journ.  and  Trans.  Md,  Coll.  Pharm.^  March, 
1861. 
HYDRIODATE  OF  AMMONIA. 
By  Murray  Thomson,  M.  D.,  F.  C.  S. 
Lecturer  on  Chemistry,  Edinburgh. 
There  are  at  present  two  methods  in  use  for  the  preparation 
of  this  salt.  One  of  these  is  the  same  as  that  given  in  the  Ed- 
inburgh Pharmacopoeia  for  the  preparation  of  iodide  of  potassium, 
only  that  the  iodide  of  iron,  which  is  first  made,  is  decomposed 
by  ammonia  or  carbonate  of  ammonia,  instead  of  by  carbonate  of 
potass.  By  separating  with  a  filter  the  insoluble  oxide  or  car- 
bonate of  iron,  the  hydriodate  of  ammonia  is  obtained  in  solution, 
which  it  is  now  only  necessary  to  evaporate,  at  not  too  high  a 
temperature,  so  as  to  obtain  the  salt.  The  other  method  is  to 
make  first  a  solution  of  hydriodic  acid,  by  passing  sulphuretted 
hydrogen  gas  into  iodine  suspended  in  water.  Hydriodic  acid 
is  thus  formed,  and  sulphur  precipitated ;  the  latter  is  sepa. 
rated  by  filtration,  and  the  acid  filtrate  is  neutralized  with 
ammonia  or  carbonate  of  ammonia,  and  then  evaporated  to 
dryness  as  before. 
In  either  of  these  ways  the  salt  may  be  made  quite  pure,  at 
least  so  far  as  obtaining  a  solution  of  it  is  concerned.  It  is  in 
the  evaporation  of  this,  so  as  to  get  the  dry  salt,  that  the  diffi- 
culty lies  in  obtaining  it  quite  colorless.  Almost  invariably  as 
the  drying  of  the  salt  is  just  being  finished,  a  slight  decomposition 
takes  place,  and  some  of  the  iodine  is  set  free,  and  communicates 
its  brown  color  to  the  whole  mass.  To  obviate  this  tendency  to 
decomposition  is  the  purpose  of  my  improvement,  and  it  con- 
sists, in  the  first  place,  in  taking  care  that  the  salt  during  the  time 
of  its  being  dried,  shall  always  contain  a  slight  excess  of 
ammonia ;  and,  secondly,  in  re-converting  the  liberated  iodine 
into  hydriodic  acid,  by  from  time  to  time  allowing  a  small 
