574         Separation  of  Iodine,  Bromine  and  Chlorine.  {^wSSjSB"*' 
When  some  of  the  powdered  substance  is  exposed  to  the  air  in  a 
shallow  layer,  the  iodine  all  volatilizes,  leaving  a  residue  of  sulphur. 
When  acted  on  by  a  solution  of  sodic  hydrate,  a  residue  of  sul- 
phur is  left,  and  the  solution  gives  very  little  precipitate  with  baric 
chloride  after  acidifying  with  hydrochloric  acid. 
The  properties  of  the  substance  seem  to  indicate  that  it  is  a 
mechanical  mixture  of  iodine  and  sulphur  and  not  a  chemical  com- 
pound. 
Some  experiments  were  then  made  with'  the  iodide  of  sulphur, 
S2I2,  described  by  Guthrie.  This  was  prepared  by  mixing  chloride 
of  sulphur,  S2C12,  with  ethylic  iodide,  and  allowing  the  mixture  to 
remain  in  a  sealed  tube  for  four  days.  Black  crystals  were  then 
found  in  the  tube.  On  opening  the  latter  a  large  quantity  of  the 
vapor  of  ethylic  chloride  escaped. 
The  crystals  were  removed  from  the  tube  and  powdered.  On 
heating  a  portion  in  a  test-tube  it  fused  at  a  temperature  a  little 
above  the  boiling-point  of  water. 
Some  of  the  substance  in  vacuo  gave  off  iodine,  leaving  a  light 
colored  residue.  Some  of  the  substance  dissolved  in  sulphide  of 
carbon  was  crystallized  fractionally  ;  the  first  crop  contained  O  38 
percent,  of  sulphur;  the  second  031;  the  third  1-07;  and  the 
fourth  3478.  On  allowing  the  mother-liquor  to  evaporate,  the 
residue  contained  76  32  per  cent,  of  sulphur. 
When  acted  on  by  a  solution  of  sodic  hydrate  the  iodine  is 
removed  and  all  the  sulphur  remains  behind,  the  solution  giving  no 
precipitate  with  baric  chloride  after  adding  hydrochloric  acid.  It  is 
usually  stated  in  text-books  that  the  compound  undergoes  a  decom- 
position similar  to  that  of  the  chloride  of  sulphur,  forming  an  iodide 
and  a  sulphite  or  thiosulphate,  with  separation  of  sulphur. 
The  fusing-point  being  lower  than  those  of  iodine  and  sulphur 
would  indicate  that  some  chemical  action  takes  place  when  the 
elements  are  mixed  together,  but  its  properties  more  resemble  those 
of  a  non-metallic  alloy  than  of  a  definite  chemical  compound. 
SEPARATION  OF  IODINE,  BROMINE  AND  CHLORINE.1 
By  C.  Schierholz. 
When  each  of  the  three  halogens  is  present  in  fair  quantity,  the 
author  adopts  an  indirect  method,  in  which  two  weighings  only  are 
1  Monatsk.,  13,  1-39  ;  Jour.  Chem.  Soc,  1892,  p.  1028. 
