152  Ferric  Chloride  and  Potassium  Iodide.  {Ami/arch, 
Pharni, 
1890. 
ft-,  and  it  is  evident  that  the  conversion  of  the  former  into  the  latter 
develops  -j-  2-74  Cal.  The  action  of  ammonia  on  the  double  salt 
just  described  develops  -f-  23-52  Cal.  if  it  has  been  prepared  from 
anhydrosulphite  a ;  -f  23  87  Cal.,  if  from  anhydfosulphite  /9 ;  and 
-f  23-87  Cal.  if  from  Marignac's  salt. 
Berthelot  has  shown  (Ann.  Own.  Phys.  [6],  iii,  242),  that  a  solu- 
tion which  contains  2  mols.  of  sulphurous  anhydride  and  1  mol.  of 
potassium  oxide  alters  spontaneously  with  development  of  -f  2-6 
Cal.,  2  mols.  of  potassium  hydrogen  sulphite  forming  1  mol.  of  the 
anhydrosulphite  with  elimination  of  water.  According  to  de  For- 
crand,  no  similar  change  occurs  with  the  sodium  salt,  but  the  fact 
that  a  similar  thermal  disturbance  is  observed  seems  to  point  to  the 
opposite  conclusion. 
The  action  of  two  successive  molecules  of  ammonium  oxide  on 
the  two  molecules  of  potassium  anhydrosulphite  develops  -\-  25-05 
Cal.  and  23  32  Cal.,  respectively,  the  corresponding  values  for  the 
a-sodium  salt  being  26-16  Cal.  and  23-52  Cal.,  and  for  the /3-salt 
23-42  Cal.  and  23-87  Cal.,  respectively.  The  fact  that  the  heat  of 
neutralization  of  the  fourth  acid  function  by  ammonia  is  less  than 
the  heat  of  neutralization  of  the  first  three,  indicates  that  the 
anhydrosulphites  contain  four  equivalents  of  metal  in  the  molecule. 
With  sodium  or  potassium  hydroxide  in  place  of  ammonia,  however, 
the  four  heats  of  neutralization  are  identical.  Nevertheless  the 
author  considers  that  this  view  is  supported  by  the  existence  of 
double  sulphites,  such  as  3MgO,Amp,4S02  -f  i8H20  and  3CdO,- 
Na20,4S02. 
REACTION  BETWEEN  SOLUTIONS  OF  FERRIC  CHLO- 
RIDE AND  POTASSIUM  IODIDE. 
By  D.  J.  Carnegie. 
The  decomposition  of  acid  solutions  of  potassium  iodide  appears 
to  be  a  function  of  time  and  temperature;  it  can  be  arrested  by 
surrounding  them  with  an  inert  atmosphere,  except  when  the 
solutions  are  strong  and  the  temperature  high. 
The  author  has  made  numerous  experiments  with  solutions  of 
potassium  iodide  and  ferric  chloride  of  known  strength,  and  although 
many  of  his  results  indicate  that  a  ratio  of  1  mol.  of  KI  to  1  atom 
1  Chem.  Arews,  lx,  87-qo ;  Jour.  Chem.  Soc.,  Dec,  1889,  11 13. 
