Am.  Jour.  Pharm.  \ 
Aug.  1, 1874.  j 
Soluble  Starc7i, 
369 
solve  it,  it  is  necessary  to  heat  it  to  boiling,  or  allow  it  to  digest  for 
half  an  hour  in  a  water-bath  at  100°  C.  Alcohol  precipitates  it  and 
also  restores  it  to  its  insoluble  state.  The  same  result  is  obtained  by 
congealing  the  solution  in  a  freezing  mixture,  it  being  found  when 
the  ice  is  melted  as  a  white  precipitate  at  the  bottom  of  the  vessel. 
When  this  substance  is  mixed  with  dextrin  and  glucose,  as  in  the 
mother  liquor  wherein  these  granules  are  formed,  all  these  properties 
disappear. 
These  artificial  starch  granules  give  with  iodine  all  the  color  reac- 
tions obtained  with  the  natural  granules  as  well  as  those  given  by 
dextrin,  according  to  the  disposition  of  their  molecules,  the  result 
being  variable  at  will.  Thus,  a  dilute  solution  takes  a  pure  red  color ; 
but  when  it  is  concentrated  to  saturation,  iodine  gives  rise  to  a  violet 
color.  If  iodine  be  added  to  a  solution  moderately  diluted,  so  as  to 
produce  a  deep  red-brown  color,  and  the  solution  be  allowed  to  evap- 
orate in  the  open  air,  it  will  gradually  grow  more  and  more  purple ; 
and  eventually,  when  sufficiently  concentrated,  become  of  a  magnifi- 
cent pure  blue  color.  If  water  be  added,  the  violet  color  reappears 
and  in  its  turn  gives  place  to  a  pure  red. 
If,  instead  of  concentrating  the  red  liquid  by  evaporation,  a  neutral 
salt  having  an  affinity  for  water,  such  as  chloride  of  calcium,  be  added, 
the  result  is  the  same.  If  the  blue  solution  be  allowed  to  stand  for 
twenty-four  hours,  it  deposits  a  blue-black  substance,  which  is  not  dis- 
dissolved  by  cold  water,  This  precipitate,  however,  appears  to  dis- 
solve in  water ;  it  does  not  affect  its  transparency,  and  passes  read- 
ily through  a  filter,  but  after  a  very  short  time  it  is  again  deposited. 
This  is  characteristic  also  of  the  iodized  granulose ;  from  which  the 
author  concludes  that  in  both  bodies  the  disposition  of  tne  molecules 
is  the  same,  and  that  they  do  not  differ  in  degree  of  cohesion. 
The  iodized  artificial  granulose  can,  in  fact,  be  destroyed,  by  a 
slight  elevation  of  temperature ;  it  enters  into  solution  in  the  water 
in  which  it  was  suspended,  and  is  then  only  colored  red  with  iodine, 
whilst  natural  granulose  resists  a  boiling  temperature  and  continues  to 
be  colored  blue  with  iodine.  The  artificial  granules  resemble  also 
natural  grains  of  starch,  in  not  being  colored  by  a  small  quantity  of 
iodine,  the  blue  only  appearing  when  it  is  in  excess ;  but  if  they  be 
triturated  in  a  mortar  with  a  small  quantity  of  iodine,  a  mass  of  a 
pure  blue  color  is  produced. 
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