412 
SYRUP  OF  HYDRIODIC  AOID. 
But  as  it  is  quite  possible  to  produce  a  salt  by  this  process  that 
shall  be  entirely  free  from  even  a  trace  of  iodate,  I  think  it  is 
only  necessary  to  guard  manufacturers  against  this  salt  occur- 
ring in  their  product,  to  make  it  suitable  for  preparing  hydriodic 
acid.  I  have  accordingly  used  an  iodide  prepared  by  the  Pharma- 
copoeia method  of  decomposing  the  solution  of  iodide  of  iron  by 
carbonate  of  potash  ;— 
THE  SYRUP. 
Take  of  Sugar  .  .  3  Ij .  3ss. 
Water  .  .  3  v. 
Dissolve  in  a  flask  with  the  aid  of  heat,  and  allow  it  to  cool. 
Prepare  solution  of  hydriodic  acid  as  before  mentioned,  without 
adding  any  of  the  additional  water.  -  This  operation  should  be 
done  speedily,  and  it  may  answer  for  that  end  to  strain  it  through 
calico.  If  paper  were  used,  decomposition  would  show  itself 
before  filtration  could  be  completed,  unless  the  quantity  was  small. 
Of  this  strong  solution  take  f.sss  and  3j.  and  mix  with  the  syrup. 
The  whole  should  measure  f.gijss.,  and  each  f.3j  contain  the 
equivalent  of  gr.ij.  of  iodine. 
Or  it  may  be  prepared  by  dissolving  the  hydriodate  and  tar- 
taric acid,  each  in  syrup  instead  of  water,  mixing  them  together 
and  letting  it  stand  for  a  few  hours  to  allow  the  bitartrate  to 
settle,  and  pouring  off  sufficient  for  the  required  quantity  of 
syrup.  With  this  latter  mode,  which  appears  the  more  feasible 
of  the  two,  a  slight  decomposition  takes  place  with  the  syrup  in 
the  first  instance,  probably  owing  to  the  quantity  of  sugar  being 
insufficient  to  preserve  it ;  but  after  being  mixed  with  the  larger 
portion  of  syrup  it  remains  unchanged. 
Syrup  of  hydriodic  acid,  by  the  first  method,  I  have  had  pre- 
pared since  the  3d  of  June,  and  it  remains  nearly  colorless.  I 
have  also  syrups  having  some  color,  which  have  been  made  for 
several  months,  that  have  the  same  appearance  as  when  first 
prepared.  In  a  syrup  prepared  early  in  the  winter  the  sugar 
has  crystallized  out  of  the  solution,  and  the  liquor  on  the  surface, 
now  weak  of  sugar,  has  a  bright  yellow  color,  and  gives  a  strong 
reaction  with  starch  j  but  the  crystallized  portion  is  not  affected 
by  it  unless  a  little  nitric  acid  is  also  added,  when  it  reacts 
strongly. 
Hydriodic  acid  being  gaseous  it  will  not  be  possible  to  procure 
it  in  a  solid  form  combined  with  sugar.    When  a  strong  solution 
