244 
CHEMICAL  EXAMINATION  OF   THE  RUBIACEiE. 
Rubitannic  acid      =C14H809,  in  the  herb  of  Rubia  tinctorum. 
Cinchonatannic  acid=C14H809,  in  the  bark  of  Cinchona  scrobi- 
culata. 
Galitannic  acid      =C14H8O10(?),  in  the  herb  of  Galium  verum. 
The  caffeotannic  acid  is  resolved,  at  an  elevated  temperature, 
into  pyrocatechine,  C12H604,  carbon  and  water.  By  the  action  of 
the  oxygen  of  the  air  in  the  presence  of  potash,  C12H605  is 
found. 
The  chinovatannic  acid  is  decomposed  by  the  action  of  acids 
into  sugar  and  chinova-red=C12H605. 
The  aspertannic  acid,  by  treatment  with  acids,  gives  a  body  of 
the  composition  C12H606. 
The  cinchonatannic  acid,  by  decomposition  in  the  air,  produces 
cinchona-red,  C12H707=C12H606+HO. 
The  tannic  acids  of  the  Galium  verum  and  aparine  and  of  the 
leaves  of  Rubia  tinctorum  are  contained  in  these  plants  in  such 
small  quantities,  that  it  was  impossible,  even  by  operating  upon 
large  quantities  of  them,  to  procure  sufficient  material  for  the  ex- 
amination of  the  products  of  their  decomposition.  The  ipecacu- 
anhic  acid  also  has  not  yet  been  examined  in  this  respect. 
From  what  has  been  here  stated,  it  follows  that  all  the  plants  of 
the  family  Rubiacece  that  have  been  investigated  contain  a  tannic 
acid  of  the  general  formula  C14H8On.  Taking  into  consideration 
the  mode  of  decompositon  of  these  substances,  this  formula  may 
be 
C12H6  ) 
written  >  O13- 
AU  the  Rubiacece  belonging  to  the  division  Stellatse,  which  were 
investigated,  contained,  together  with  the  characteristic  tannic  acids, 
in  all  the  parts  which  were  examined,  rubichloric  and  citric  acids. 
Rubichloric  acid,  according  to  its  composition,  is  immediately  al- 
lied to  these  tannic  acids;  it  contains  carbon  and  hydrogen  in  the 
same  proportion.  Its  formula  is  C14H809;  it  is  decomposed  by  the 
action  of  acids  at  a  high  temperature  into  formic  acid  and  chlor- 
C12H6  } 
rubine,  so  that  its  formula  maybe  written  thus  : — ^2  ^2  r  O9.  ^n 
its  properties,  however,  it  differs  completely  from  the  tannic  acids  ; 
it  is  not  colored  green  by  perchloride  of  iron,  &c. 
Citric  acid  must  be  considered  as  a  characteristic  constituent  of 
