THE 
AMERICAN  JOURNAL  OF  PHARMACY. 
JULY,    1  8  6  2. 
ON  ALKALINE  IODIDES  AND  BROMIDES. 
By  Ferdtnand  F.  Mayer. 
In  preparing  these  salts,  since  a  direct  combination  of  the 
halogens  with  the  alkaline  metal  is  not  practicable,  they  are 
usually  combined  with  hydrogen  or  some  less  positive  metal, 
from  which  the  salts  are  then  formed  by  being  brought  together 
with  caustic  or  carbonated  alkalies. 
From  the  cheapness  of  the  material,  iron  has  most  generally 
been  selected  to  form  the  intermediate  combination,  various 
methods  being  employed  to  reduce  the  bulk  of  the  precipitated 
oxyd,  among  which  are  that  of  the  Dublin  Pharmacopoeia,  and 
the  process  known  as  Griepenkoven's  and  Buchner's,  which  was 
originally  suggested  by  Liebig. 
These  methods  require  partly  caustic  alkalies,  and  are  rather 
circumstantial ;  and  because  the  alkaline  sulphates  are  always 
obtainable  free  from  chlorides,  which  in  the  carbonates  tend  to 
deteriorate  the  quality  of  the  product,  Liebig  has  lately,  in  the 
instance  of  the  iodides,  recommended  the  preparation  of  calcium 
or  baryura  salts,  by  saturation  with  hydriodic  acid,  as  the  in- 
termediate stage,  from  which  pure  alkaline  salts  are  readily  ob- 
tained by  precipitation,  partly  with  the  sulphates,  partly,  and  to 
complete  the  reaction,  with  carbonates. 
The  hydriodic  acid  used  for  the  purpose  is  its  mixture  with 
phosphoric,  formed  by  the  simultaneous  action  of  phosphorus  and 
iodine  on  water,  and,  as  we  have  it  from  the  accounts  of  M. 
Pettenkofer  and  W.  S.  Squire,  the  process  is  expeditious  and 
not  at  all  expensive.     There  are,  however,  several  objections 
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