246 
CHEMICAL  EXAMINATION  OF  THE  RUBIACEiE. 
I.  Characteristic 
constituent. 
Tannic  acid  of  the  for- 
mula- 
c2 
II.  Cinchonacese. 
II.  Characteristic 
constituent. 
III.  Characteristic 
constituent. 
7  or  9. 
On.n  =  6  or  7. 
Kinic  acid —  Kinovic  acid — 
C]2H6  >  n8  Cl2H903. 
C2  H2  ) 
III.  Coffeacece. 
II.  Characteristic  III.  Characteristic 
constituent.  constituent. 
"Wanting.   Citric  acid      =  C12H6012, 
Kinovic  acid    =  C,2H903, 
Gum  andstarch=CI2H10O10. 
%      I.  Characteristic 
constituent. 
Tannic  acid  of  the  for-  w  anting.   Uitnc  acia       =  u  ~n  u  ~,  or 
mula-  Kinovic  acid    =  C,2H903,  or 
C12H6 
C2H2; 
As  regards  the  quantity  of  the  characteristic  tannic  acids  ex- 
isting in  the  different  groups,  the  largest  quantity  is  found  in  the 
Coffieacese  and  Cinchonacese,  although  for  the  most  part  already 
changed  by  the  influences  to  which  the  parts  of  the  plants  have 
been  exposed  before  they  reach  us.  In  the  Stellatse  the  quantity 
of  these  acids  is  very  small,  especially  in  Galium  aparine  and 
the  leaves  of  Rubia  tinctorum. 
If  these  tannic  acids  be  considered  with  regard  to  their 
amount  of  oxygen,  it  appears  that  this  is  greatest  in  those  plants 
which  inhabit  the  temperate  zones,  such  as  the  Stellatse,  or 
which  grow  at  greater  elevations,  like  the  Cinchonse,  which 
flourish  on  the  Andes  at  from  4000  to  8000  feet  above  the  level 
of  the  sea  ;  whilst  it  is  small  in  the  tannic  acids  of  plants  inhab- 
iting hot  climates,  such  as  Cephaelis  ipecacuanha,  Coffea  arabica 
and  Qhiococca  racemosa.  While  the  tannic  acids  of  the  Stellatse 
contain  8.10  equivs.  of  oxygen,  those  of  the  true  Coffeacese  have 
only  6.T  equivs.;  so  that  the  deoxidation  goes  further  in  high 
temperatures  than  in  colder  climates. 
With  regard  to  those  plants,  which,  together  with  a  tannic 
acid,  contain  also  an  acid  of  the  formula  Cl4H8On,  it  appears  that 
they  only  differ  in  their  composition  by  1  equiv.  of  oxygen,  so 
that  by  the  separation  of  1  equiv.  of  oxygen,  the  one  acid  might 
pass  into  the  other.  Their  different  properties  and  mode  of  de- 
composition sufficiently  show  that  they  are  not  to  be  considered 
as  different  oxides  of  the  same  radical.  The  author  here  com- 
pares together  the  acids  which  are  contained  in  the  same  plant. 
