414  ON  THE  DETECTION  OF  IODINE. 
ham  came  into  general  use,  this  domestic  article  would  serve  the 
twofold  purpose  of  a  teapot  and  a  "  perfume  vaporizer."  Doubt- 
less if  these  leaves  can  be  obtained  in  quantities  sufficient  for 
consumption  as  tea,  the  French  perfumers  might  also  import 
them  to  advantage,  if  for  no  other  use.  Powdered,  they  would 
make  excellent  sachets. 
In  the  Museum  at  Kew  are  some  cigars  made  of  the  leaves  of 
A.  fragrans  simply  rolled  in  a  thin  tobacco  leaf.  They  are 
probably  very  agreeable  smoking,  but  I  am  unable  to  say  if  this 
application  is  a  common  one  in  the  island  of  Bourbon,  or  whether 
these  specimens  are  rather  a  curiosity. — Lond.  Pharm.  Journ., 
July,  1866,  from  Gardeners'  Chronicle. 
ON  THE  DETECTION  OF  IODINE. 
By  M.  Carey  Lea. 
Where  iodine  exists  in  the  form  of  hydriodic  acid,  or  the 
iodide  of  a  base,  two  methods  are  commonly  employed  to  put  it 
into  a  condition  to  be  detected  by  the  starch  test.  One  of  these 
is  by  the  action  of  nitric  acid,  the  other  by  chlorine  or  bromine 
water.  The  latter  is  the  more  delicate,  but  has  the  disadvantage 
that  if  the  chlorine  or  bromine  be  added  in  excess,  the  reaction 
is  missed. 
It  occurred  to  me,  while  engaged  in  testing  for  iodine,  that  the 
facility  with  which  that  body  is  eliminated  from  its  hydrogen 
and  metallic  combinations  by  chromic  acid  would  make  the 
latter  substance  a  valuable  means  of  bringing  about  the  starch 
reaction,  and  a  few  experiments  completely  confirmed  this 
view. 
If,  for  example,  we  take  an  extremely  dilute  solution  of  iodide 
of  potassium,  such  that  the  addition  of  nitric  acid  and  starch  pro- 
duces no  perceptible  effect,  the  further  addition  of  a  single  drop 
of  very,  dilute  solution  of  bichromate  of  potash  will  instantly 
bring  about  the  characteristic  reaction. 
When  chlorhydric  acid  is  substituted  for  nitric,  the  effect  of 
the  bichromate  is  (as  was  to  be  expected)  still  more  marked.  The 
test  has  then  the  full  delicacy  at  least  of  the  chlorine  test,  with 
this  great  advantage,  that  an  excess  of  the  reagent  does  not 
prevent  the  reaction. 
