CHEMICAL  EXAMINATION  OF  THE  RUBIACE^E. 
247 
The  tannic  acid  in  Portlandia  grandiflora,  Cl4H807,  may  be 
formed  from  the  kinic  acid,  C'4  H808,  by  the  loss  of  1  equiv.  of 
oxygen;  as  may  the  kinic  acid,  C14H808,  of  the  Cinchona  scro. 
bieulata  from  its  cinchonatannic  acid,  C,4H809;  the  aspertannic 
acid,  C,4H808,  of  the  Asperula  odorata  from  its  rubichloric  acid, 
Cl4H809;  and  the  rubichloric  acid,  Cl4H809,of  the  Galium  verum 
from  its  galitannic  acid,  C14H8Ol0. 
The  rubitannic  acid  of  the  Rubia  tinctorum  may  pass  directly 
into  the  isomeric  rubichloric  acid.  The  occurrence  of  acids  with 
12  equivs.  of  carbon,  such  as  citric  and  kinovic  acids,  together 
with  acids  of  the  formula  C14H8On,  as  well  as,  on  the  other  hand, 
the  readiness  with  which  the  acids  containing  14  equivs.  of  car- 
bon pass  into  substances  with  12  equivs.  of  carbon,  appears  to 
render  it  probable  that  these  acids  with  12  equivs.  of  carbon  are 
the  materials  from  which  the  acids  with  14  equivs.  are  formed, 
although  hitherto  no  one  has  succeeded  in  forming  a  tannic  acid 
from  citric  or  kinovic  acid. 
If  the  hydrate  of  citric  acid,  C12H6012,  were  to  assimilate  1 
equiv.  of  formic  acid  and  give  off  oxygen,  the  formation  of  the 
tannic  acids  of  the  Rubiacese  might  be  effected, — Citric  acid  = 
Cl2H6Ol2-fC2H204,  formic  acid=Cl4H8016. 
C^H8016— 06=CI4H8010,  the  tannic  acid  of  Galium  verum. 
OH8016— 07=Cl4H8Q9,  the  rubichloric  acid  of  the  Stellatw, 
or  the  tannic  acids  of  the  cinchona  bark  and  of  the  Rubia  tinc- 
torum. 
C^4H8016— 08=Cl4H808,  the  kinic  acid  of  the  Cinchonaceee, 
or  the  tannic  acid  of  Asperula. 
Cl*H8016— 09=Cl4H807,  caffeotannic  acid,  or  the  tannic  acid 
of  the  Cinchona  nova  bark. 
C^H8Ol6— Ol0=Cl4H8OG,  the  tannic  acid  of  the  Ipecacuanha 
root. 
In  this  manner  the  kinovic  acid,  Cl2H903,  might  be  transformed 
into  these  acids  by  the  assimilation  of  oxalic  acid  and  oxygen^ 
Cl2H903+C203==C14H906.  If  1  equiv.  of  water  be  separated, 
there  remains  C  4H805,  which  united  with  1  equiv.  oxygen  might 
form  ipecacuanhic  acid,  with  two  equivs.,  the  caffeotannic  acid, 
and  so  on. 
That  kinovic  acid  is  capable  of  assimilating  other  compounds 
is  shown  by  the  investigation  of  caincic  acid,  which  consists  of 
