ON  THE  ODOR  OF  COMMERCIAL  TANNIC  ACID. 
53 
ON  THE  ODOR  OF  COMMERCIAL  TANNIC  ACID. 
By  WiLLrAM  Procter,  Jr. 
The  following  query  was  accepted  by  the  writer  : — "  Pure  tan- 
nic acid  being  an  odorless  substance,  is  there  an  odorous  sub- 
stance in  nutgalls,  that  is  found  adhering  to  commercial  tannic 
acid  ?  or  is  the  odor  commonly  noticed  in  that  substance  due  to 
impure  ether  used  in  its  preparation  ?" 
According  to  Dr.  Wood  (U.  S.  Disp.)  "galls  are  inodorous." 
Pereira  says,  "  Galls  have  no  odor."  (Elements,  page  323,  vol. 
II.  Am.  Edit.)  Christison  also  says,  "  Galls  are  without  odor." 
Notwithstanding  these  opinions,  at  least  two  of  these  authorities 
give  volatile  oil  as  one  of  the  ingredients  of  nutgalls. 
My  own  examination  of  galls  induces  the  opinion  that,  in 
their  whole  and  dry  condition,  they  have  but  little  odor  where 
they  are  in  a  box  or  drawer ;  when,  however,  galls  are  bruised, 
or  in  a  powder,  a  distinct  odor  is  manifest,  which  is  well  marked, 
though  not  very  prominent.  When,  therefore,  ordinary  alcoholic 
*  ether  is  allowed  to  percolate  powdered  galls,  it  should  remove  this 
odorous  substance  along  with  the  tannic  acid  and  green  and  brown 
coloring  matters,  and  deposit  them  on  evaporation  with  any  im- 
purities the  ether  may  contain. 
To  put  this  matter  to  a  practical  test,  a  bottle  of  ether  was 
procured  from  Dr.  Squibb,  which  left  hardly  a  trace  of  odor 
when  evaporated  on  a  surface.  This  was  mixed  with  a  due  pro- 
portion of  alcohol  and  water,  and  passed  through  powdered  galls. 
The  ethereal  percolate  was  evaporated  to  dryness  in  a  capsule, 
with  sufficient  heat,  until  the  ether  was  dissipated.  The  residue, 
when  dry  and  brittle,  was  rubbed  to  powder.  It  had  a  greenish 
color,  and  a  decided  odor  of  bruised  nutgalls,  but  no  odor  of  im- 
pure ether. 
A  portion  of  this  tannin  was  digested  in  benzine,  in  which 
liquid,  tannic  acid  is  insoluble,  and  on  evaporating  the  benzine 
in  a  glass  capsule,  until  the  odor  of  that  substance  entirely  dis- 
appeared, a  minute  residue,  possessing  the  well  marked  odor  of 
nutgalls,  remained  in  the  capsule. 
The  inference,  therefore,  is,  that  the  odor  of  commercial  tannic 
acid  is  chiefly  due  to  the  odorous  principle  of  nutgalls,  to  which 
