56 
IODIDE  OF  ALUMINUM. 
Iodide  of  aluminum  behaves  exactly  like  the  chloride.  It  dis- 
solves in  water  with  strong  evolution  of  heat,  forming  a  fluid 
which  rapidly  becomes  brown  in  the  air.  It  is  also  soluble  in 
absolute  alcohol. 
The  aqueous  solution  may  be  evaporated  in  vacuo  over  sulphu- 
ric acid,  and  under  certain  circumstances  a  perfectly  white  mass 
may  thus  be  obtained.  The  iodide  of  aluminum  is  treated  with 
little  water  so  as  to  produce  a  clear  oily  solution  ;  this  is  then 
quickly  placed  under  the  bell  of  the  air-pump,  and  as  complete  a 
vacuum  as  possible  is  produced.  A  radiately  crystalline  film  is 
soon  formed,  and  in  a  short  time  this  becomes  an  enamel-like 
mass.  When  touched  with  a  glass  rod,  the  mass  which  is  still 
tenaciously  fluid,  then  often  solidifies  with  a  distinct  evolution  of 
heat.  The  solid  mass  remains  without  alteration  under  the  bell- 
glass  with  sulphuric  acid  ;  it  does  not  fume  in  the  air,  deliquesces 
readily,  and  dissolves  without  residue  in  water.  When  heated 
in  a  glass  tube  it  is  decomposed ;  water,  hydriodic  acid,  and  free 
iodine  are  evolved,  leaving  alumina  in  the  residue.  It  is  there- 
fore probably  a  hydrate  of  the  periodide  ;  the  author  proposes  to 
determine  its  composition  more  exactly. 
Iodide  of  Potassium  and  Aluminum,  KI-f-API3,  is  produced 
when  iodide  of  aluminum  in  the  form  of  vapor  is  brought  into 
contact  with  heated  iodide  of  potassium  in  a  sealed  tube.  This 
compound  has  the  appearance  of  a  waxy,  transparent,  crystalline 
mass,  which  fuses  readily,  but  appears  to  be  very  difficult  to 
volatilize.  It  is  not  decomposed  by  being  strongly  heated,  but 
only  parts  with  a  small  excess  of  iodide  of  aluminum  with  great 
difficulty ;  for  this  purpose  the  temperature  must  be  raised  until 
the  softening  of  the  glass.  In  water  it  dissolves  without  residue, 
producing  much  heat.    Analysis  : — ■ 
I  88-59  4  88-42 
Al  5-26  2  4-77 
K  5-76  1  6-81 
Ohem.  Graz.,  Oct.  15,  1857,  from  Pogg endoff's  Annalen. 
