4o8  Standard  for  Desiccated  Thyroid  ^l<iiids  \^^^^:J^^^l;J'\^^^^^^^ 
convenience  of  execution.  r\n*thennore,  from  the  point  of  view 
of  the  Pharmacopoeia  it  possesses  the  advantage  over  the  JUiumann 
method  that  no  analytical  procedures,  volumetric  solutions,  or 
reagents,  new  to  the  present  edition  of  the  Pharmacopoeia,  are 
required. 
In  his  original  paper  ^  Dr.  Hunter  gives  very  clear  and  explicit 
descriptions  of  all  the  details  of  the  process,  and  there  is  conse- 
quently little  opportunity  for  uncertainty  in  regard  to  any  part 
of  the  method.  It  is  the  rule,  however,  in  Pharmacopoeial  descrip- 
tions of  analytical  processes,  that  only  the  essential  features  be 
included,  consequently  it  appears  desirable  that  a  concise  description 
of  the  Hunter  method,  in  what  may  be  called  Pharmacopoeial 
language,  be  given.    Such  an  outline  would  be  as  follows : 
Determination  of  Iodine  (Hunter  Method). — One  gram  of 
Desiccated  Thyroid  Gland  is  mixed  in  a  nickel  crucible  of  about 
125  c.c.  capacity,  with  15  grams  of  a  mixture  composed  of  138 
parts  by  weight  of  anhydrous  KXO.^,  106  parts  anhydrous  NaoCO. 
and  75  parts  KNOg,  and  an  additional  5  grams  of  this  fusion 
mixture  spread  evenly  over  the  surface.  The  crucible  is  then  heated 
over  a  free  Bunsen  flame  until  no  further  carbonization  is  observed, 
it  is  cooled  and  the  friable  residue  dissolved  in  about  150  c.c.  of 
distilled  HoO.  To  this  solution  contained  in  an  Erlenmeyer  flask 
of  about  500  c.c.  capacity,  is  added  approximately  50  c.c,  or  its 
equivalent,  of  fresh  liquor  sodae  chlorinatae  U.  S.  P.  (containing 
2.4  wt.  per  cent.  CI).  The  mixture  is  then  treated  with  enough 
phosphoric  acid  ( i  volume  of  the  85  per  cent,  syrup  and  i  volume 
of  H2O),  to  produce  a  marked  yellow  tint  of  free  chlorine,  and  an 
additional  10  c.c.  of  the  phosphoric  acid  is  then  added  and  the  con- 
tents of  the  flask  boiled  for  about  one-half  hour  or  until  the  volume 
has  been  reduced  to  about  150  c.c.  The  liquid  is  cooled,  10  c.c. 
of  I  per  cent,  aqueous  KI  solution  is  added  and  the  liberated 
iodine  titrated  with  N/200  sodium  thiosulphate,  adding  starch  paste 
as  the  indicator  just  before  the  end  of  the  reaction.  The  N/200 
thiosulphate  may  be  made  by  diluting  25  c.c.  of  exactly  N/io 
thiosulphate  to  500  c.c. ;  it  changes  strength  rapidly  and  should 
be  prepared  fresh  at  each  time  determinations  are  made.  One  c.c. 
of  N/200  thiosulphate  corresponds  to  0.0001058  gm.  iodine  derived 
from  the  sample  of  thyroid  used. 
This  method  has  been  tested  in  this  laboratory  in  comparison 
^  Hunter :  Jour.  Biol.  Chem.,  7,  321-349,  1910. 
