^pfeSS'}     Black  and  White  Mustard  Seed.  437 
Solutions. — (1)  Potassium  Iodide  Solution  (5  per  cent.),  5  grammes 
of  crystallized  pure  potassium  iodide  are  dissolved  in  water  to  make 
100  c.c. 
Iodine  Test  Solution  U.S. P.  (2  per  cent.). 
Directions. — Put  I  gramme  of  the  powdered  black  mustard  seed 
into  a  perfectly  dry  test  tube ;  add  10  c.c.  of  the  above  potassium 
iodide  solution  and  boil.  Cool,  and  carefully  add  to  the  surface  of 
the  bright  yellow  liquid  from  one  to  three  drops  of  iodine  test  solu- 
tion, U.S. P.,  taking  care  to  allow  it  to  flow  down  the  side  of  the 
tube,  upon  the  surface  of  the  liquid.  The  contrast  in  color  between 
the  iodized  part  and  the  lower  liquid  is  very  striking,  and  plainly 
visible  with  as  little  as  o-i  per  cent,  of  starch. 
Remarks. —  The  blue  coloration  by  this  method  is  perhaps  not 
quite  as  permanent  as  in  the  copper  experiments,  yet  it  is  suffi- 
ciently characteristic  at  the  time  of  its  formation,  and  for  a  reason- 
able time  afterward. 
Summary  for  Black  Mustard  Seed. — (1)  Four  methods  have  been 
indicated  which  we  submit.  As  before  stated,  the  potassium  iodide 
test  (Test  III),  seems  to  us  to  be  preferable. 
(2)  The  potassium  iodide  test  (Test  III)  indicates  the  presence  of 
0*2  per  cent,  of  starch,  with  all  certainty,  and  of  01  per  cent,  by 
closely  observing  the  contrast  in  color. 
(3)  Hence  the  following  recommendation  is  made  . 
{a)  If  not  more  than  1  per  cent,  of  starch  (in  the  form  of  starch- 
bearing  seeds,  etc.)  is  considered  admissible  in  black  mustard  of 
commerce,  the  Pharmacopoeia  should  demand  that : 
When  mixed  thoroughly  with  nine  times  its  weight  of  powdered 
black  mustard  seed,  previously  ascertained  to  be  free  from  starch, 
the  mixture,  if  submitted,  in  the  quantity  of  one  gramme,  to  the  test 
indicated  under  Test  III,  should  not  give  a  plain  blue  starch  reaction. 
(b)  If  it  is  desirable  to  make  the  pharmacopceial  limit  lower  than 
I  per  cent,  of  starch,  a  correspondingly  smaller  amount  of  starch- 
free  mustard  seed  should  be  added. 
[c]  If  pure  black  mustard  free  from  starch  is  demanded,  by  the 
U.S.P.  when  submitted  to  the  foregoing  test  (Test  III),  it  should 
show  no  blue  reaction. 
WHITE  MUSTARD  SEED. 
The  odor  of  oil  of  mustard  (allyl  mustard  oil)  is  not  developed 
when  powdered  white  mustard  is  boiled  with  water,  a  fact  which 
