AmMJaT'x87h8arm'}  The  Origin  of  Tragacanth.  1 29 
easily  explain  the  presence  of  starch.  But,  evidently,  if  the  recognition 
of  such  an  easily  recognizable  body  has  been  so  difficult,  it  is  even 
more  so  to  recognize  the  nature  of  the  main  constituent  which  imparts 
to  tragacanth  its  principal  properties.  Indeed,  much  confusion  has 
existed  on  this  point,  and  we  are  therefore  the  more  rejoiced  at  meet- 
ing with  researches  by  Giraud,  by  which  an  unexpected  light  is  shed 
on  it. 
If,  says  the  author,  1  part  of  tragacanth  is  digested  in  50  parts  of 
water,  containing  1  per  cent,  of  hydrochloric  acid,  the  liquid  filtered 
and  then  mixed  with  baryta  water  in  excess,  the  gradually  deposited 
precipitate  will  consist  of  pectate  of  barium.  If  this  is  collected, 
washed,  diffused  in  water  and  then  treated  with  muriatic  or  acetic  acid, 
the  base  will  dissolve,  while  the  residue  will  consist  of  pectic  acid.  In 
this  manner  tragacanth  will  yield  60  per  cent,  of  pectic  acid.  The 
process  described  shows  plainly  that  pectic  acid  does  not  pre-exist  in 
tragacanth,  but  is  formed  from  some  other  substance.  Giraud  explains 
as  follows : 
1.  A  very  small  percentage  of  tragacanth  only  is  soluble  in  cold 
water,  not  30  to  50  per  cent.,  as  is  sometimes  stated.  The  soluble 
portion  is  not  a  substance  similar  to  arabin,  but  a  mixture. 
2.  If  tragacanth  is  digested,  in  a  water-bath,  with  50  times  its  weight 
of  water,  the  entire  gummy  constituent  is  transformed  into  a  soluble 
gum,  which  after  having  been  dried  will  not  swell.  The  new  product 
is  not  arabin,  but  pectin. 
3.  By  subjecting  this  principle,  with  water  containing  1  per  cent,  of 
acid,  to  the  heat  of  a  water-bath  for  two  or  three  hours,  it  becomes 
entirely  soluble,  but  still  consists  mainly  of  pectin,  and,  though  precip- 
itated by  alcohol,  is  not  gum,  as  usually  stated.  Sugar,  formed  simul- 
taneously, amounts  to  scarcely  one-tenth  of  the  substance  employed. 
These  experiments  show  that  tragacanth  is  transformed  by  these 
processes  into  pectin,  which  is  soluble  in  water,  precipitated  by  alcohol, 
and  by  alkalies  converted  into  pectates  and  metapectates.  The  pectin 
is  generated  from  an  insoluble  pectinous  principle,  which  constitutes 
more  than  one-half  of  the  tragacanth,  and  is  apparently  identical  with 
Fr^my's  pectose. 
It  is  well  known  that  pectose  occurs  largely  in  the  tissues  of  many 
fruits  and  roots  ;  it  accompanies,  nearly  always,  cellulose,  with  which, 
however,  it  cannot  be  confounded  ;  for  by  the  action  of  acids  eellulose 
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