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SYRUP  OF  HYDRIODIC  ACID. 
SYRUP  OF  HYDRIODIC  ACID. 
By  Mr.  James  Murdoch. 
Hydriodic  acid  in  a  liquid  form  has  been  introduced  into 
medicine  by  Dr.  Andrew  Buchanan,  as  having  the  therapeutical 
powers  of  iodine  without  its  irritant  action.  It  has  also  been 
employed  by  him  in  the  treatment  of  choleraic  disease,  and  ac- 
cordingly becomes  a  preparation  of  considerable  interest. 
The  following  speedy  formula  he  has  given  for  preparing  it : — 
Take  of  Tartaric  acid,  264  grains, 
Iodide  of  Potassium,  330  grains. 
Dissolve  each  separately  in  f.  gjss.  of  distilled  water ;  mix  the 
solutions,  agitate  and  strain  to  separate  the  bitartrate  of  potash, 
adding  water  to  make  up  the  measure  to  f.  gvjj.  Each  fluid 
drachm  of  this  solution  should  contain  5.072  grains  of  hydriodic 
acid,  equal  to  about  5  grains  of  iodine.  When  the  solutions  are 
mixed  the  liquid  assumes  a  slight  yellow  color,  and  in  ten  minutes 
after  gives  a  slight  tinge  of  violet  with  a  cold  solution  of  starch, 
which  gradually  changes  to  a  deep  blue. 
This  rapid  decomposition  appears  to  arise  in  some  measure  from 
the  agitation  necessary  to  effect  the  separation  of  the  bitartrate, 
and  consequently  greater  contact  with  the  air.  When  hydriodic 
acid  is  prepared  by  the  sulphuretted  hydrogen  process,  it  does  not 
show  decomposition  for  an  hour  or  two  after  it  is  prepared ;  but 
if  moderately  agitated  it  shows  the  presence  of  free  iodine  much 
more  speedily.  It  is,  therefore,  essential  in  dispensing  this  acid, 
to  prepare  it  extemporaneously  and  supply  it  frequently  to  obtain 
its  medicinal  action.  It  may  very  speedily  be  prepared  by  the 
above  process ;  and  for  convenience  the  solutions  may  be  kept 
ready  made  and  mixed  when  required ;  but  as  264  grains  of  tar- 
taric acid  in  f.  Hiss,  of  distilled  water  measures  f.  3xv.,  and  330 
grains  of  iodide  of  potassium  in  the  same  quantity  of  water, 
measures  f.  5x1V.,  it  will  be  necessary  to  employ  them  in  these 
relative  proportions.  Dr.  Buchanan  also  directs  it  to  be  taken 
in  starch  gruel,  which  has  the  chemical  effect  of  combining  with 
the  iodine  that  is  liberated  during  the  time  of  its  administration. 
I  find  that  hydriodic  acid  may  be  prevented  from  undergoing 
this  decomposition  when  in  the  form  of  a  syrup. 
The  antiseptic  properties  of  sugar  are  well  known  t^  the 
