442  IODINE  IN  MINERALS,  PLANTS  AND  ANIMALS. 
Zahorowitz  (Moravia,)  Bristol,  Salzschlirf,  Tatenhausen  (West- 
phalia,) Caledonia  spring  (Canada.) 
Sea  water  contains  so  little  iodine  that  Tennant,  H.  Davy, 
Gaultier,  Fyfe  and  Sarphati,  were  unable  to  detect  its  presence. 
However,  Balard  found  it  in  the  Mediterranean  water,  and  Pfaff 
in  that  of  the  Baltic,  which  is  very  poor  in  iodine.  Tornt  and 
Herapath  found  only  doubtful  traces  of  iodine  in  the  water  of 
the  Dead  Sea,  and  Dugeud  believes  that  the  water  of  the  Olden- 
burgh  marsh  contains  iodine.  From  what  has  already  been  stated 
as  to  the  presence  of  iodine  in  marine  plants  and  animals,  it  will 
be  seen  that  they  appropriate  iodine  in  considerable  quantity  as 
iodide  of  potassium,  sodium,  calcium  or  magnesium. 
Chatin  detected  iodine  in  rain  and  fresh  water,  0-0002  to 
0-0005  in  ten  liters.  The  rain  water  from  the  interior  of  France 
contained  far  more  iodine  than  that  which  fell  near  the  sea,  and 
after  long-continued  rain  the  water  was  free  from  iodine. 
The  usual  method  formerly  adopted  for  the  detection  of  iodine 
was  to  add  starch  paste  to  the  liquid  to  be  tested  and  then  nitric 
acid,  which,  by  liberating  the  iodine,  gave  rise  to  the  production 
of  the  characteristic  blue-colored  compoumd  of  iodine  and  starch. 
Instead  of  nitric  acid,  chlorine  water  may  be  used  to  liberate  the 
iodine,  but  it  must  be  added  with  great  caution,  because  an  ex- 
cess destroys  the  blue  color  so  readily  that  minute  traces  of  iodine 
may  be  overlooked.  Nitric  acid  does  not  itself  produce  this 
effect,  but  when  the  iodide  is  accompanied  by  a  large  quantity  of 
chloride  it  liberates  chlorine  at  the  same  time,  so  that  in  such 
cases  the  cautious  application  of  chlorine  water  is  preferable. 
A  solution  of  nitrate  of  palladium  is  recommended  by  Las- 
saigne  as  a  reagent  for  iodine.  The  protiodide  of  palladium  is 
black,  insoluble,  and  is  deposited  only  after  some  time. 
A.  Reynoso  proposes  to  separate  iodine  and  bromine  from 
metals  which  prevent  its  reaction  with  starch  by  means  of  a  sub- 
stance, which  does  not,  like  chlorine,  combine  with  it.  He  uses 
peroxide  of  barium,  a  piece  of  which  is  mixed  in  a  test-tube  with 
water,  hydrochloric  acid  and  starch  paste,  and  when  the  evolu- 
tion of  gas  commences,  the  liquid  to  be  tested  for  iodine  is  added. 
When  chlorides,  sulphurets,  sulphites,  or  hyposulphites  are  pre- 
sent, their  influence  as  regards  the  reduction  of  peroxide  of  hy- 
drogen may  be  counteracted  by  using  a  larger  quantity  of  per- 
