Am.  Jour.  Pharm.  \ 
Nov.  1892.  J 
Iodides  of  Sulphur. 
573 
iron -ammonia  alum  and  is  regulated  so  that  I  cc.  ~  -00 1  gm.  P2Os 
being  titrated  preferably  with  a  solution  of  phosphate  of  ammo- 
nium, 2  9439  gm.  to  a  litre.  After  obtaining  the  phosphates  in 
solution  (iron,  aluminium  and  manganese  being  eliminated),  it  is 
exactly  neutralized  with  a  caustic  alkali,  using  phenolphthalein  as 
indicator ;  to  this  solution  is  added  a  small  quantity  of  salicylic 
acid  and  the  above  reagent  is  used  for  titration.  Toward  the  end  of 
the  operation  it  is  best  to  allow  the  precipitate  to  settle,  so  as  to 
observe  with  better  advantage  the  end  of  the  reaction,  which  is 
indicated  by  a  violet  coloration. 
ON  THE  IODIDES  OF  SULPHUR1 
By  Prof.  Herbert  McLeod,  F.  R.  S. 
An  iodide  of  sulphur,  SI6,  isomorphous  with  iodine,  was  prepared 
by  Landolt  and  measured  crystallographically  by  Vom  Rath 
{Poggendorff  's  Annalen,  cx,  1 1 6).  It  was  made  by  allowing  a  solu- 
tion of  iodine  and  sulphur  in  carbonic  disulphide  to  evaporate  spon- 
taneously. As  the  existence  of  this  compound  has  been  adduced 
as  a  proof  of  the  hexad  character  of  sulphur,  it  seemed  advisable  to 
investigate  its  properties. 
Some  of  the  substance  was  prepared  by  the  process  mentioned, 
and  in  order  to  separate  it  from  any  admixture  of  iodine,  it  was 
placed  in  a  tube  which  was  afterwards  exhausted  by  the  Sprengel 
pump  and  sealed.  One  end  of  the  tube  was  then  surrounded  by 
muslin  kept  wet  with  water  by  means  of  a  piece  of  cotton  wick  ; 
iodine  volatilized,  at  first  rapidly  but  afterwards  more  slowly.  After 
the  lapse  of  three  months  a  residue  was  left  at  the  end  of  the  tube 
which,  on  analysis,  was  found  to  contain  98-5  per  cent,  of  sulphur. 
Another  quantity  was  dissolved  in  carbon  disulphide  and  the 
solution  allowed  to  evaporate  ;  as  crystals  were  formed  the  liquid 
was  poured  off  and  the  crystals  washed  with  carbonic  disulphide. 
In  this  manner  five  crops  of  crystals  were  obtained,  none  of  which 
contained  more  than  half  a  per  cent,  of  sulphur ;  the  residue  left  on 
allowing  the  mother-liquor  to  evaporate  contained  56  per  cent,  of 
sulphur. 
The  iodine  is  entirely  removed  from  the  substance  by  digesting 
it  in  a  solution  of  potassic  iodide. 
1  Read  before  the  British  Association,  Edinburgh  Meeting,  1892,  Section  B, 
reprinted  from  Chem.  News,  Sept.  2. 
