440 
ON  AFEICAN  TRAGACANTH. 
in  polarized  light  by  means  of  the  microscope.  In  this  respect 
the  tragacanth  of  Sterculia  differs  from  that  of  Astragalus.  A.s 
a  means  of  promoting  the  adhesiveness  of  pilular  masses  I  find 
the  former,  whether  in  the  form  of  powder  or  mucilage,  as 
advantagous  as  ordinary  tragacanth'. 
The  fine  powder  on  exposure  for  some  days  to  a  temperature 
of  212°  F.  looses  20-50  per  cent  of  its  weight.  The  formula 
C12H22O11+5H2O  would  exactly  require  20*5  per  cent,  of  water. 
It  is  not  soluble  in  an  ammoniacal  solution  of  peroxide  of  copper; 
repeatedly  boiled  with  fuming  nitric  acid  it  affords  an  abundance 
of  mucic  acid. 
The  weight  of  the  powder  as  obtained  by  drying  it  at  212°  F. 
does  not  diminish  at  230°  F.  (110°  C).  Upon  incineration,  the 
dried  powder  leaves  7*8  per  cent,  of  ash  of  which  the  prevailing 
constituent  is  carbonate  of  calcium  ;  0-122  gramme  of  the  ash 
indeed  contain  (after  having  been  previously  moistened  with  a 
solution  of  carbonate  of  ammonium  and  again  gently  heated,  in 
order  to  prevent  any  loss  of  carbonic  acid)  0*0587  gramme  car- 
bonic acid.  The  amount  of  the  basic  part  of  the  ash  is  accor- 
dingly 4-08,  referring  to  100  parts  of  the  above  powder. 
The  dried  and  powdered  gum  was  now  submitted  to  elemen- 
tary analysis*  by  means  of  peroxide  of  copper  and  a  current  of 
oxygen. 
r.  In  the  first  experiment  0-3412  gramme  yielded  0-5066  and  0-1648. 
II.       "    second     "         0-2982      "  "       0-4380    "  0-1524. 
that  is  to  say 
I.  0-1374  of  carbon  and  0  01831  of  hydrogen. 
II.  0-1195        "        "    001693  " 
accordingly  the  percentage  is  in         I.  II. 
Carbon  ....  4027  40-06 
Hydrogen    ....  5-37  5-91 
These  numbers,  however,  referring  to  the  crude  tragacanth, 
must  be  calculated  with  regard  to  the  fact,  that  100  parts  of  the 
raw  drug  correspond  to  95-92  parts  only  of  pure  tragacanth,  if 
we  deduct  the  above  4*08  per  cent,  of  the  bases  contained  in  the 
ash. 
*  Performed  in  my  laboratory  by  Dr.  Kraushaar. 
