196  Observations  on  Acacia  of  Commerce.  {AmAprii,'f897?m' 
to  state  that  they  are  presented  solely  on  account  of  the  interest 
which  they  seem  to  possess  for  the  practical  pharmacist,  with  the 
consciousness  that,  considered  as  a  scientific  investigation,  the 
important  factor,  completeness,  is  lacking. 
According  to  the  U.  S.  Pharmacopoeia,  acacia  is  "  a  gummy  exu- 
dation from  Acacia  Senegal,  Willdeiiow  (nat.  ord.  Leguminosce). 
Besides  the  description  of  the  physical  appearance  of  the  gum,  the 
following  tests  are  also  given  : 
(a)  Acacia  should  be  soluble  in  2  parts  of  water;  it  should  yield  a 
gelatinous  precipitate  with  basic  lead  acetate,  T.  S.,  ferric  chloride, 
T.  S.,  or  concentrated  solution  of  sodium  borate,  and  does  not 
reduce  alkaline  cupric  tartrate,  V.  S. 
(b)  The  powder  is  not  colored  blue  (absence  of  starch),  or  red 
(absence  of  dextrin),  by  iodine,  T.  S. 
In  addition  to  these  tests,  it  may  be  of  interest  to  refer  to  two 
others  for  the  presence  of  dextrin. 
One,  which  is  from  Hager,  Hartwich  and  Fischer's  Commentar 
zur  Pharm.,  B.  II,  p.  44,  is  as  follows : 
"  Three  c.c.  of  a  solution  composed  of  1 5  drops  of  solution  of  fer- 
ric chloride,  15  drops  of  saturated  solution  of  potassium  ferricyan- 
ide,  5  drops  of  diluted  hydrochloric  acid  (sp.  gr.  1-165)  anc*  60  c.c. 
of  distilled  water,  are  added  to  6  c.c.  of  a  solution  of  the  suspected 
gum  (strength  of  solution  should  be  20  per  cent).  If  the  gum  be 
devoid  of  dextrin,  it  will  be  colored  a  pure  yellowish-brown  tinge, 
this  color  remaining  permanent  during  eight  to  ten  hours.  If  dex- 
trin be  present,  the  color  will  change  in  about  one  hour  to  blue." 
The  other  test,  which  is  evidently  a  modification  of  the  above 
method,  is  described  in  El  Memorandum} 
It  seems  to  be  erroneous,  inasmuch  as  it  contains  potassium  ferro- 
cyanide  instead  of  potassium  /<?mcyanide,  in  presence  of  ferric 
chloride.  The  sulphuric  acid  present  in  the  solution  does  not 
prevent  the  precipitation  of  ferric  ferrocyanide.  This  test  seems, 
therefore,  inapplicable. 
The  foregoing  are  the  tests  upon  which  the  examination  of  sam- 
ples of  commercial  gum  arabic  was  based. 
While  I  was  examining  samples  of  the  powdered  gum  in  regard 
to  their  action  upon  alkaline  cupric  tartrate,  V.  S.,  I  noticed  that, 
1  Pharm.  Jour.,  October  12,  1895,  p.  322,  and  Proc.  Am.  Pharm.  A ssoc,  Vol 
44,  P-  625. 
