42 
ON  ACIDUM  HYDEIODICUM  DILUTUM. 
Take  of  Iodide  of  Potassium  209f  grs. 
Tartaric  Acid,  in  crystals,  190J  grs. 
Dissolve  the  iodide  of  potassium  in  three  fluidrachms  of  dis- 
tilled water,  and  the  tartaric  acid  in  the  same  quantity,  and 
filter  if  necessary  ;  mix  the  solutions,  and  set  the  mixture  into 
ice  cold  water,  allow  it  to  stand  for  one  hour,  then  filter,  and 
make  up  the  measure  to  two  fluid-ounces. 
The  formula  is  based  on  actual  calculation,  and  each  fluidrachm 
of  the  solution  of  the  acid  represents  ten  grains  of  iodine. 
Hydriodic  acid  is  readily  obtained  by  the  various  methods 
given  for  its  preparation.  The  greatest  difficulty  is  to  preserve 
it,  and  it  was  found  impossible  to  do  this  without  recourse  to 
chemical  means.  An  article  on  syrupus  ferri  iodidi,  published 
in  the  American  Journal  of  Pharmacy  for  March,  1868,  first 
suggested  the  use  of  hyposulphite  of  soda  for  this  purpose  ;  it 
was  tried,  and  found  to  answer  very  well.  Its  use  in  such  small 
quantities  is  supposed  to  be  unobjectionable,  since  it  can  have 
no  influence  upon  the  medicinal  application  of  the  acid.  A 
solution  is  made  containing  sixty  grains  of  hyposulphite  of  soda 
to  the  fluidounce  of  distilled  water;  of  this,  five  drops  was  found 
sufficient  to  restore  a  two  ounce  sample  of  highly-colored  acid, 
and  to  keep  it  so  to  the  present  time,  a  space  of  three  months. 
How  much  less  of  this  solution  would  preserve  a  newly  made 
acid  from  change  in  keeping  could  not  be  determined  for  want 
of  time. 
This  query  may,  therefore,  be  answered  in  the  judgment  and 
experience  of  the  writer, 'that  the  officinal  process  is  not  the 
best  for  medicinal  uses,  though  it  may  be  the  best  for  more 
strictly  chemical  purposes,  and  that  a  slight  modification  of 
the  process  of  Dr.  Buchanan  of  Glasgow  is  better;  and  fur- 
ther, that  the  acid  may  be  either  protected  or  restored  by  the 
use  of  one-third  of  a  grain  of  crystallized  hyposulphite  of  soda, 
or  less,  to  the  fluid-ounce,  provided  this  be  considered  unobjec- 
tionable. 
Brooklyn,  Sept.  5th,  1868. 
— Proc.  Amer.  Pharm.  Assoc,^  1868. 
