CHEMICAL  CONSTITUTION  OF  FLAKE  MANNA.  401 
ON  THE  CHEMICAL  CONSTITUTION  OF  FLAKE  MANNA. 
By  M.  H.  Buignet. 
The  author  has  made  a  very  elaborate  investigation  of  the 
constituents  of  flake-manna,  which  is  published  in  the  June  and 
July  numbers  of  the  Journal  de  Pharmacie. 
The  following  are  the  conclusions  arrived  at : — 
1.  Flake  manna  in  its  natural  state  possesses  a  very  ener- 
getic rotatory  power.  This  power  is  dextrogyrate ;  its  value, 
brought  to  the  plane  of  polarization  of  the  yellow  ray  is  ex- 
pressed by  [a]  j  =  +  28°  40'. 
2.  The  rotatory  power  of  manna  does  not  depend  on  the 
saccharine  matter  it  contains,  because  it  is  found  to  remain  the 
same  after  the  destruction  of  all  the  sugar  by  fermentation. 
8.  The  substance  to  which  this  rotatory  power  is  due  is  dex- 
trine, which  has  not  been  before  isolated  by  chemical  analysis 
from  manna,  and  which  forms  nevertheless  one  of  the  principal 
elements  of  its  composition.  It  constitutes  about  one-fifth  of 
flake  manna  and  a  much  larger  proportion  of  the  different 
species  of  manna  in  sorts.  It  can  easily  be  extracted.  It 
then  offers  all  the  physical  and  chemical  characters  of  pure  dex- 
trine. 
4.  The  saccharine  matter  (besides  the  mannite)  in  flake  manna 
consists  of  a  mixture  of  cane  sugar  and  uncrystallizable  sugar. 
These  two  sugars  are  found  united  in  such  proportion  that  they 
mutually  neutralize  their  opposite  optical  properties. 
5.  The  different  species  of  manna  found  in  commerce  all 
contain  sugar  and  dextrine.  The  absolute  quantity  of  these  two 
principles  varies  considerably  one  species  with  another,  but  their 
relative  proportion  is  constant  and  invariable.  Thus  in  various 
samples  of  flake  manna  as  well  as  of  the  varieties  of  sorts,  there 
is  always  found  two  equivalents  of  dextrine  to  one  equivalent  of 
sugar. 
6.  By  the  nature  and  proportion  of  these  elements,  the  mix- 
ture of  sugar  and  dextrine  in  manna  resembles  the  ordinary 
product  of  the  saccharification  of  starch.  It  is  therefore  prob- 
able that  it  is  derived  from  starch  by  a  natural  process,  simula- 
ting that  used  in  the  laboratory  by  diastase  and  gentle  heating. 
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