26 
Sterculia  Gum. 
Am.  Jour.  Pharm, 
Jan  ,  1890. 
Exped.  into  the  Interior  of  Trop.  Australia/'  etc.,  p.  155.  These 
remarks  are  signed  by  J.  L. — Dr.  Lindley. 
A  specimen  of  the  naturally  exuded  gum  in  the  Technological 
Museum  is  remarkably  like  paraffin  in  appearance,  and  almost  as  free 
from  color.  It  is  rather  tough  and  horny,  and  breaks  with  a  dull 
fracture.  In  the  mouth  I  fail  (except  in  the  shape  of  the  pieces)  to 
detect  any  difference  between  it  and  tragacanth.  It  is  in  irregular 
pieces,  full  of  angles  and  points,  the  result  of  the  fusion  of  innumera- 
ble tears. 
A  mass  swells  up  readily  in  water  and  then  disintegrates.  The  insol- 
uble portion  has  a  granular  appearance  similar  to  that  which  pearl- 
sago  of  exceeding  fineness  assumes  under  similar  circumstances.  The 
jelly  is  of  snowy  or  rather  icy  whiteness,  freer  from  color  than  the 
jelly  yielded  by  the  best  isinglass,  and  of  enormous  bulk  when  the 
absorption  of  water  is  complete. 
This  gum  and  tragacanth  present  many  points  of  difference.  Their 
closest  similarity  is  in  outward  appearance.  Sterculia  gum  does  not 
thicken  water,  except  to  a  barely  appreciable  extent,  and  therefore 
could  not  have  the  economic  uses  to  which  the  very  viscid  tragacanth 
is  put.  On  treating  the  gums  with  cold  water,  a  difference  between 
them  is  the  more  bluish  opalescent  appearance  of  tragacanth,  and  the 
granular  appearance  of  the  mucilage  afforded  by  Sterculia.  But  these 
gums  may  be  at  once  distinguished  by  the  canary-yellow  color  yielded 
by  adding  caustic  soda  to  mucilage  of  tragacanth  and  boiling,  no  col- 
oration being  observable  in  the  case  of  Sterculia  gum. 
The  author  then  repeated  the  whole  of  Giraud's  experiments  on 
tragacanth,  as  detailed  in  Phar.  Journ.  [3],  v,  766  ;  viii,  773,  and 
he  may  at  once  state  that  he  obtained  with  tragacanth  all  the  general 
results  recorded  by  that  chemist.  He  then  repeated  the  experiments, 
with  substitution  of  Sterculia  gum  for  tragacanth,  and  he  presents  his 
results  in  the  form  of  comparative  statements  : 
S  imilarities —  Qualitative. 
1.  Horny  texture. 
2.  They  swell  enormously  in  water. 
3.  The  jellies  redden  litmus. 
4.  They  dissolve  on  prolonged  boiling  in  a  large  quantity  of  water. 
5.  They  dissolve  on  boiling  in  dilute  hydrochloric  acid. 
Quantitative. 
6.  They  contain  about  20  per  cent,  of  water. 
