Am  lour.  Pharm.  ) 
Dec,  1878  / 
A  New  Double  Iodide. 
577 
NOTES  ON  A  NEW  DOUBLE  IODIDE. 
By  Frederick  W.  Fletcher,  F.C.S 
Read  at  the  British  Pharmaceutical  Conference. 
The  strong  tendency  exhibited  by  many  of  the  iodides  to  form 
double  salts  is  well  known.  Within  the  last  ten  days  a  new  and  strik- 
ing instance  of  this  characteristic  feature  has  come  under  my  notice, 
and  the  compound  produced  is  in  many  respects  so  remarkable,  that  I 
venture  to  submit  the  few  notes  which  I  have  been  able  to  make 
respecting  it,  to  the  consideration  of  the  Conference. 
In  experimenting  upon  a  complex  solution,  which  amongst  other 
things  was  known  to  contain  a  salt  of  quinia,  I  was  somewhat  aston- 
ished to  find  a  copious  scarlet  precipitate  produced  on  the  addition  of 
potassium  iodide.  The  color  was  not  sufficiently  vivid  for  that  of 
mercuric  iodide,  and  with  the  exception  of  the  little-known  but  curious 
double  iodide  of  mercury  and  copper,  no  iodide  with  a  like  appearance 
produced  under  similar  conditions,  suggested  itself. 
Having  collected  and  washed  the  precipitate,  I  proceeded  to  examine 
it  qualitatively,  when  it  was  found  to  contain  besides  the  halogen,  bis- 
muth and  quinia.  Solutions  of  these  last  two  substances  were  then 
prepared  and  mixed,  and  I  found  that  not  only  in  each  case  was  this 
brilliant  precipitate  obtained  on  the  instant  that  an  iodide  was  intro- 
duced, but  that  by  experimentally  regulating  the  proportions  of  the 
three  salts,  it  was  possible  to  remove  the  whole  of  the  quinia,  the  bis- 
muth and  the  iodine  from  the  solution  in  the  form  of  this  beautiful 
double  salt. 
A  few  ounces  of  the  compound  having  been  carefully  prepared,  I 
submitted  a  portion  to  analysis  in  order  to  ascertain  the  relative  propor- 
tions in  which  the  elements  present  were  combined,  and  thus  arrive  at 
its  proper  formula. 
The  bismuth  was  thrown  down  from  a  solution  of  the  salt  in  ammo- 
nium citrate  containing  excess  of  acid,  by  hydrogen  sulphide,  1  gram 
yielding  -322  gram  Bi2S3>  equivalent  to  26*2  per  cent,  of  metal. 
The  quinia  was  estimated  in  a  similarly  prepared  solution  by  Allen's 
ether  method,  a  process  which  always  gives  unexceptionable  results. 
1  gram  of  the  salt  yielded  *202  gram  anhydrous  quinia,  or  20#2  per 
cent. 
The  iodine  was  separated  as  a  silver  salt,  1  gram  yielding  '989  gram 
Agl,  equal  to  53*4  per  cent,  of  iodine. 
37 
