294 
ON  ALKALINE  IODIDES  AND  BROMIDES. 
iodine,  one  half  of  the  iron,  and  sufficient  water,  into  a  flask,  and 
when  all  the  iodine  and  lithia  are  dissolved,  add  the  remainder 
of  the  iron,  boil  up,  and  proceed  as  directed  for  Iodide  of  Sodium. 
Iodide  of  Calcium. 
Take  of  Precipitated  Carbonate  of  Lime,  200  parts. 
Iodine,  S81  « 
Iron  in  filings,  112  " 
Water,  a  sufficient  quantity, 
and  proceed  as  directed  for  iodide  of  lithium. 
From  the  iodide  of  calcium,  or,  if  need  be,  iodide  of  baryum 
prepared  in  the  same  manner,  all  the  other  iodides  are  prepared 
by  precipitation  with  the  sulphates  or  carbonates  of  their  re- 
spective metals. 
[The  carbonate  of  lime,  which  is  added  in  excess  and  does 
therefore  not  all  dissolve,  must  be  free  from  chloride  and  magnesia. 
It  is  then  preferable  to  burnt  lime  in  the  form  of  milk,  as  this 
is  rarely  free  from  the  latter  impurity.  The  coloration  of  these 
iodides  when  evaporated  appears  to  be  owing  to  the  presence  of 
iodide  of  magnesium,  which  is  decomposed  during  that  opera- 
tion.] 
Preparation  of  Bromides. 
The  action  of  bromine  on  caustic  and  carbonated  alkalies,  to- 
gether with  ferrous  salts  or  metallic  iron,  is  in  every  respect 
analogous  to  that  of  iodine.  The  proportions  for  the  various 
salts,  which  are  prepared  precisely  in  the  manner  directed  for 
the  iodides,  are  as  follows : 
'  Bromide  of  Potassium. 
Take  of  Bicarbonate  of  Potassa,    400  parts. 
Bromine,  320  " 
Iron  in  filings,  112  « 
Water,  a  sufficient  quantity. 
Bromide  of  Sodium. 
Take  of  Crystallized  Carbonate  of  Soda,    572  parts. 
Bromine,  320  " 
Iron  in  filings,  112  " 
Water,  a  sufficient  quantity. 
