280 
Active  Principle  of  Polygonum  Hydropiper.  {AmjJ^; 
Pharm. 
1556. 
animal  charcoal  repeatedly,  until  all  coloring  matter  is  removed.  The 
nitrate  is  then  treated  with  a  solution  of  gelatin,  in  order  to  remove 
any  tannic  acid  that  might  be  present,  again  filtered  and  evaporated 
to  dryness,  redissolved  in  ether  and  the  ethereal  solution  allowed  to 
evaporate  spontaneously. 
Polygouic  acid  thus  prepared  crystallizes  in  needles  (see  figure  i. 
Polygonic  acid  from  ethereal  solution.   X  700. 
Its  solution  in  water  does  not  precipitate  gelatin  nor  produce  a  bluish 
green  discoloration  when  added  to  a  mixture  of  ferrous  and  ferric 
salts  in  solution,  showing  absence  both  of  gallic  and  tannic  acids.  It 
is  freely  soluble  in  water,  less  so  in  ether,  and  insoluble  in  petroleum 
spirit.  The  heat  of  a  water-bath  does  not  destroy  any  of  its 
properties. 
I  may  state  here  that  the  smart -weed  employed  by  me  was  nor 
selected  by  "an  expert  botanist  fully  familiar  with  the  requirements 
of  the  case/'  but  was  selected  by  myself  :  therefore  I  know  there  can 
be  no  doubt  whatever  about  the  species  of  smart- weed  employed  in 
my  analysis. 
Xow,  as  I  have  shown  that  polygonic  acid  is  not  identical  with 
tannic  and  gallic  acids,  it  remains  for  the  learned  investigator-  to 
explain  how  it  happened  that  they  made  such  an  unpardonable  mis- 
take.   I  presume  it  was  due  to  imperfect  manipulation. 
Louisville,  Ky. 
