average 
•001775  •OOlSSS 
^'"'Dec'l.isssl''"'""^  Iodine  in  Cod  Liver  Oil.  .  613 
Mr.  Mitchell  Bird  (Pharm.  Journ.,  [2],  i.,  p.  546)  gives  results  of 
analyses  of  six  varieties  of  cod  liver  oil,  whicli  are  much  nearer  what 
I  believe  to  be  the  truth.  The  method  and  the  results  differ  consider- 
ably from  mine,  although  we  are  both  agreed  in  the  fact  that  we  have 
found  iodine  in  all  the  specimens  examined. 
The  precentage  results  are  as  follows,  the  iodine  being  calculated  as 
potassium  iodide : 
As  KI  As  Iodine. 
1.  Cod  liver  oil,  Norway  •0021  ") 
2.  Cod  liver  oil,  Norway  '0018 
3.  Cod  liver  oil,  Norway  -0016 
4.  Cod  liver  oil,  Norway  •OOIG 
5.  Cod  li  ver  oil,  Newfoundland  ^0012  i  average. 
6.  Cod  liver  oil,  Newfoundland  •OOM  i  '0013  ^000993 
He  used  5,000  grs.  of  the  oil  for  each  experiment  and  saponified  with 
alcoholic  solution  of  caustic  potash,  burned  the  soap  formed  and  dis- 
solved out  the  salts  ;  after  saturating  the  solution  with  sulphuric  acid 
and  separating  the  potassium  sulphate  deposited,  he  employed  the  starch 
test,  setting  free  the  iodine  with  nitrite  of  potassium  and  sulphuric 
acid,  and  comparing  the  color  with  standard  solutions  of  potassium 
iodide.  My  method  is  different ;  it  is  a  delicate  process  of  very  general 
application  and  one  that  I  adopted  some  years  ago,  having  discarded 
all  others  in  its  favor.  I  will  describe  it  here  as  applied  to  kelp,  one 
of  the  most  troublesome  and  various  of  all  commercial  substances  to 
sample  and  test. 
To  insure  an  accurate  sample,  about  100  lbs.  are  carefully  picked  from 
a  cargo  of  say  100  tons,  and  ground  up.  Of  this  100  grains  are 
taken  to  estimate  the  moisture,  and  another  100  grains  to  estimate 
the  soluble  matter — the  potash  and  the  iodine.  The  kelp  is  treated 
with  about  4  ounces  of  hot  water,  which  dissolves  little  or  none  of  the 
oxysulphides ;  this  operation  is  repeated,  the  residue  washed,  and  the 
solution  made  up  to  5,000  grains  measure.  Of  this  one-tenth  part,  or 
500  grains  measure,  equal  to  10  grains  of  kelp,  is  taken  for  estimating 
the  iodine,  so  that  we  never  operate  on  more  than  one-tenth  of  a  grain 
of  iodine,  generally  one-twentieth,  often  one-hundredth.  In  fact,  if 
the  amount  present  exceeds  one-tenth  of  a  grain,  we  always  dilute  the 
solution.  One  hundred  grains  measure  of  bisulphide  of  carbon  are 
added,  and  a  few  drops  (1  to  3)  of  nitrosulph uric  acid  ^  dropped  in. 
^  The  nitrosulphuric  acid  is  made  by  treating  starch  with  nitric  acid  and 
passing  the  nitrous  fumes  into  sulphuric  acid,  1843  sp.  gr.  to  saturation. 
The  mixture  keeps  very  well. 
