72 
Soluble  Gum  of  Tragacanth. 
Am,  Jour.  Pharm, 
Feb.,  1889. 
ON  THE  SOLUBLE  GUM  OF  TRAGACANTH. 
By  John  M.  Maisch. 
Read  at  the  Pharmaceutical  Meeting,  January  15. 
From  an  attentive  student  at  a  College  of  Pharmacy  a  letter  was 
recently  received  as  follows  : 
"  While  comparing  your  "  Manual  of  Organic  Materia  Medica  " 
with  the  United  States  Pharmacopoeia  I  find  a  point  where  your  book 
diifers  from  the  latter.  You  state  that  the  fluid  portion  of  the  gela- 
tinous mass,  obtained  by  treating  tragacanth  with  water,  is  precipi- 
tated by  alcohol,  while  the  Pharmacopoeia  says,  this  is  not  so.  Is 
this  statement  of  the  Pharmacopoeia  correct  ?  " 
My  attention  having  thus  again  been  called  to  this  statement  of  the 
Pharmacopoeia,  it  was  determined  to  repeat  an  experiment  frequently 
made  in  former  years.  Some  thin  flakes  of  white  tragacanth  were 
washed  with  cold  water,  and  then  soaked  in  sufficient  water  without 
applying  heat ;  cold  water  was  then  added  from  time  to  time  with  agi- 
tation, until  the  gelatinous  mass  remained  sufficiently  thin  after  stand- 
ing for  some  time  to  permit  the  fluid  portion  to  be  separated  by  means 
of  a  wetted  filter.  On  pouring  some  alcohol  upon  the  clear  filtrate, 
both  layers  remained  clear  also  at  the  point  of  contact,  and  on  mixing 
the  two  liquids,  the  transparency  of  the  mixture  was  apparently  not 
disturbed  immediately ;  but  on  close  examination  the  formation  of  a 
transparent  jelly  could  easily  be  distinguished,  and  this  separated  after 
a  while  in  the  form  of  whitish  flocks  rising  to  the  surface.  The  re- 
sult corroborates  that  of  experiments  previously  placed  on  record  by 
others,  and  proves  that  a  portion  of  tragacanth  is  soluble  in  cold  water, 
and  that  this  solution  is  precipitated  by  alcohol.  In  performing  this  ex- 
periment, it  is  necessary  to  avoid  the  use  of  heat,  since  tragacanth  al- 
ways contains  starch  which  would  be  dissolved  by  hot  water. 
It  seemed  of  interest  to  ascertain,  if  possible,  how  the  error  alluded 
to  crept  into  the  United  States  Pharmacopoeia.  Very  probably  it  was 
copied  from  the  British  Pharmacopoeia  of  1867,  as  will  be  seen  by 
comparing  the  texts  of  the  two  authorities  : 
B.  P.,  1867.  U.  S.  P.,  1880. 
....   Swelling  into  a  gelatinous  .  .  .  Swelling  with  water  to  a  gela- 
mass  which  is  tinged  violet  by  tincture  tinous  mass,  which  is  tinged  blue  by 
of  iodine.    After  maceration  in  cold  test  solution  of  iodine,  and  the  fluid 
water  the  fluid  portion  is  not  precipi-  portion  of  which  is  not  precipitated 
tated  by  the  addition  of  rectified  spirit.  on  the  addition  of  alcohol. 
The  close  similarity  in  the  phraseology  of  these  sentences  leaves 
scarcely  any  doubt  about  the  origin  of  the  last  one.    The  same  error 
