AmApriir,'i897arm"}     Observations  on  Acacia  of  Commerce.  197 
in  every  instance,  a  marked  reduction  was  taking  place.  A  repe- 
tition of  the  experiments  verified  this  observation.  I  decided  to 
apply  the  test  to  a  sample  of  the  whole  gum.  For  this  purpose  the 
best  gum  (answering  the  Pharmacopceial  description  in  physical 
appearance)  obtainable  was  employed.  One  gramme  was  pulver- 
ized in  a  clean  mortar,  and  dissolved  in  10  c.c.  of  recently  distilled 
water. 
Just  sufficient  potassium  hydrate  solution  was  added  to  give  an  al- 
kaline reaction,  and  this  solution  heated  with  alkaline  cupric  tartrate, 
V.  S.,  in  a  water-bath  (boiling  temperature),  during  twenty  minutes. 
Here,  too,  a  well-defined  reduction  was  observed,  though  seemingly 
less  prominent  than  that  produced  by  an  equal  amount  of  the  pow- 
dered substance.  When  the  test  solution  was  heated,  without  the  so- 
lution of  gum,  for  an  equal  length  of  time,  it  remained  clear.  A  like 
behavior  of  acacia  is  described  in  Hager,  Hartwich  and  Fischer's  Com- 
mentary as  follows :  "Acacia  does  not  reduce  Fehling's  solution  at 
6o°-yo°,  but  has  a  reducing  action  after  being  boiled  with  the  rea- 
gent," and  "  dried  gum  in  solution  reduces  Fehling's  solution  at 
temperature  of  water  bath."  I  have  observed,  however,  that  gum, 
not  otherwise  than  air-dried,  reduces  Fehling's  solution  without 
being  boiled,  upon  heating  a  solution  for  some  time  at  water  bath 
temperature. 
The  increased  reduction  by  the  powdered  gum  is  probably  due  to 
drying  previous  to  powdering  it. 
The  iodine  test  for  dextrin  and  starch  was  applied  to  each 
sample  in  powder  and  in  the  form  of  solution.  When  applied  to  the 
same  powder  it  imparts  to  the  powder  only  a  light  yellowish  color 
of  the  iodine.  If  only  traces  of  dextrin  are  present  a  dark  red  tint 
is  produced.  When  a  larger  quantity  of  dextrin  is  present,  the  color 
produced  by  a  few  drops  of  the  reagent  is  almost  black.  If  starch 
and  dextrin  be  present  in  the  same  sample,  they  can  hardly  be  dis- 
tinguished. One  minim  of  the  official  T.  S.  of  iodine  will  produce  a 
decisive  tint  in  solution  of  dextrin  in  distilled  water,  in  proportion 
of  1  of  the  former  to  2,000  of  the  latter.  The  presence  of  gum 
does  not  interfere  with  this  reaction. 
As  commercial  dextrin  is  not  a  product  of  definite  composition 
and  constant  proportions,  the  delicacy  of  the  iodine  test  may,  of 
course,  vary  accordingly. 
As  all  the  samples  of  gum  gave  negative  results  with  iodine, 
