Am 'juTy'i8P84arm'}         Chemical  Nature  of  Starch  Grains.  371 
CONTRIBUTION  TO  THE  MORE  EXACT  KNOWLEDGE 
OF  THE  CHEMICAL  NATURE  OF  STARCH-GRAINS. 
By  B.  Brukner. 
In  1856,  Nageli  extracted  a  substance  turned  blue  by  iodine,  and 
termed  "  granulose,"  from  starch-grains,  without,  however,  destroying 
their  form.  In  1859  Jessen  found  that  on  rubbing  starch -grains  with 
water  a  portion  of  the  soluble  starch  was  dissolved.  Nasse,  in  1866? 
gave  the  name  amidulin  to  a  soluble  body  obtained  from  starch-paste. 
Nageli,  in  1874,  extracted  by  dilute  hydrochloric  acid  a  body  essen- 
tially different  from  starch,  which  he  called  amylodextrin.  The  first 
object  of  the  author  is  to  determine  the  relation  existing  between  these 
four  bodies. 
Amidulin. — Starch  has  generally  been  considered  as  insoluble  in 
water.  Jessen  and  Delffs,  by  rubbing  starch  with  water,  extracted  a 
portion ;  this  might,  however,  have  been  due  to  the  conversion  into 
starch-paste  by  the  heat  evolved  in  the  crushing  of  the  granules. 
W.  Nageli  imbedded  starch-grains,  and  then  cut  sections ;  the  portions 
of  the  granules  were  turned  blue  by  iodine,  as  also  was,  to  some 
extent,  the  small  quantity  of  water  employed,  and  hence  a  portion 
must  have  gone  into  solution.  By  rubbing  dry  starch  granules,  they 
may  be  broken,  and,  if  subsequently  treated  by  water  and  filtered, 
they  give  a  clear  solution  turned  blue  by  iodine.  But,  on  allowing 
wheaten  starch  to  digest  with  water  for  three  weeks,  filtering,  evapo- 
rating to  one-fifth,  and  testing  with  iodine,  no  blue  coloration  was 
obtained ;  hence  it  is  impossible  to  extract  the  inner  and  soluble 
starch  with  water  until  the  outer  membrane  is  either  changed  or 
broken  :  the  character  of  the  solution  is  that  of  a  micellar  solution  ; 
it  is  not  capable  of  diffusion.  The  substance  soluble  in  cold  water 
and  colored  blue  by  iodine,  the  amidulin  of  Nasse  and  the  granulose 
of  Nageli,  are  identical. 
Starch-paste. — Schimper  and  Nageli  are  not  agreed  as  to  the  dis- 
tinction between  swollen  starch  and  starch-paste.  Between  these  two 
states  there  is  no  sharp  distinction ;  thus  at  46°  potato-starch  swells 
distinctly;  at  59°  it  begins  to  lose  its  form;  and  at  62*5°  it  is  con- 
verted into  a  paste,  and  shows  no  trace  of  the  original  form.  After 
discussing  Niigeli's  micellar  theory,  viz.,  that  the  smallest  particles  of 
starch  and  similar  substances  consist  not  of  molecules,  but  of  larger 
