136 
Tannins  of  Oak-Bark. 
f  Am.  Jour.  Pharm. 
\      March,  1884. 
being  freed  from  adhering  moisture  by  drying  at  110°,  gives  off  a 
further  quantity  of  water  at  130-140°. 
Quercitannic  acid  is  represented  by  the  formula  C17H1609.  At 
130-140°,  it  gives  off  water,  and  is  converted  into  the  brown-red 
anhydride,  C34H30O17  =  2C17H1609  —  H20,  identical  with  the  phlo- 
baphene  contained  in  the  bark.  1  mol.  of  this  substance  boiled  with 
sulphuric  or  hydrochloric  acid  gives  up  1  mol.  water,  and  is  converted 
into  a  second  anhydride,  C34H28016;  and  by  boiling  the  tannic  acid  free 
from  anhydrides  with  either  of  these  anhydrides,  a  third  anhydride, 
C34H2S015,  is  obtained.  These  three  anhydrides  are  soluble  in  alcohol 
and  in  caustic  alkalis. 
Lowe  ("Amer.  Jour.  Phar."  1881  p.  401,  1882  p.  118,)  by  treating 
quercitannic  acid  or  phlobaphene  with  dilute  sulphuric  acid,  or  with 
oxalic  acid,  has  obtained  a  fourth  anhydride,  03tH24O14=2C17H16O9 — 
4H20,  which  he  designates  as  oak-red.  The  same  name  has  been  applied 
to  the  first  anhydride  by  Oser,  and  to  the  second  by  Bottinger. 
Another  oak-bark  examined  by  the  author  yielded  a  tannic  acid 
having  the  composition  C20H20O9,  and  agreeing  with  the  former  in  all 
its  properties,  excepting  in  its  reaction  with  ferric  chloride,  with  which 
it  gives  a  bluish  green  color,  quickly  changing  to  deep  green,  and  on 
addition  of  sodium  carbonate,  first  to  blue  and  then  to  red,  whereas 
the  quercitannic  acid  above  described,  and  all  its  anhydrides,  give  with 
ferric  chloride  a  black-blue  precipitate.  This  tannic  acid  begins  to 
lose  water  at  124°,  melts  at  140°,  resolidifies  on  further  loss  of  water, 
and  is  converted  into  a  brown-red  substance  identical  in  composition 
with  phlophene. 
The  tannic  acid,  C20H20O9,  also  yields  four  anhydrides  agreeing  in 
character  with  those  obtained  from  the  acid  C17H16Og.  These  anhy- 
drides are  represented  by  the  formulae  C40H38O17,  C4(JH36016,  C40H34O15, 
and  C40H32O14.  The  same  tannic  acid  heated  in  a  sealed  tube  with 
hydrochloric  acid  yielded  a  gas  burning  with  a  green  flame,  but 
smaller  in  quantity  than  that  obtained  from  the  acid  C17H1609.  Heated 
in  a  tube  with  dilute  sulphuric  acid,  it  gave  a  red  liquid  and  a  large 
quantity  of  undissolved  anhydrides;  and  on  agitating  this  liquid  with 
ether  a  small  quantity  of  crystals  was  obtained  consisting  of  gallic 
acid. 
The  phlobaphene  submitted  to  dry  distillation,  yielded  pure  catechol, 
free  carbon,  and  an  oil  insoluble  in  potash,  smelling  like  the  terpenes 
and  containing  72*46  per  cent.  C  and  7*11  H.    This  oil,  oxidized  with 
