84 
The  Starch  Grain. 
{  Am.  Jour.  Pharm. 
V  February,  1914. 
swollen.  Besides  the  entire  mass  is  more  or  less  granular,  while 
in  the  case  of  the  other  starches  examined  the  charred  mass  is  in 
a  puffed  condition. 
The  effects  produced  when  starch  is  heated  in  the  presence 
of  a  fixed  oil,  as  almond  oil,  are  of  special  interest.  The  inner 
structure  of  the  starch  grain  is  not  usually  apparent  when  it  is 
mounted  in  a  fixed  oil,  unless  the  starch  has  been  previously  heated 
to  a  temperature  of  from  8o°  to  1600  C.  When,  however,  a  mixture 
of  starch  and  oil  is  heated  as  high  as  i8'o  C.  the  grains  still  polarize 
light,  which  shows  that  the  structure  has  not  been  altered.  In 
other  words  the  effects  of  heat  on  the  grain  are  more  or  less 
neutralized  by  the  presence  of  the  oil.  On  heating  the  mixture  up 
to  2500  C.  most  of  the  grains  still  show  their  individual  character, 
but  no  longer  polarize  light.  They  are  but  slightly  swollen,  and 
in  the  case  of  cassava  and  corn  starch  a  central  differential  area 
occupies  from  one-half  to  nine-tenths  of  the  original  area  of  the 
grain. 
It  may  be  worth  while  to  state  that  when  starch  and  water 
in  the  proportion  of  2  gm.  of  the  former  to  100  c.c.  of  the  latter, 
are  heated  together  at  a  temperature  of  between  900  and  ioo°  C. 
in  a  steam  sterilizer  seven  or  eight  hours  a  day  for  a  long  period, 
even  extending  to  months,  dextrinization  of  the  starch  does  not 
take  place,  that  is,  the  solution  still  gives  a  blue  color  with  iodine. 
Even  though  the  operation  be  conducted  in  an  autoclave  under 
a  pressure  of  20  pounds  for  about  ten  hours,  dextrinization  is 
not  effected.  If,  however,  1  c.c.  of  N/HC1  be  added  to  100  c.c. 
of  water  and  this  heated  for  five  hours  with  1  gm.  of  starch,  the 
resulting  solution  is  colored  red  with  iodine.  When  the  amount 
of  the  acid  is  reduced  to  .2  c.c.  and  the  mixture  heated  under 
a  pressure  up  to  12  pounds  for  one  hour,  cassava,  corn,  maranta 
and  potato  starch  solutions  give  a  deep  blue  color  with  iodine, 
while  a  solution  of  wheat  starch  gives  a  deep  purple  color  with 
iodine.  If  the  heat  be  continued  an  hour  longer,  wheat  starch 
gives  a  purplish-red  color,  cassava  a  deep  wine  color,  maranta 
and  potato  a  light  purple,  while  corn  still  gives  a  blue  reaction 
with  iodine. 
These  observations  may  be  summarized  as  follows : 
1.  The  starch  grain  consists  of  two  nearly  related  substances: 
(a)  a  colloidal  or  mucilage-like  substance  which  takes  up  aniline 
