546 
EXAMINATION  OF  KINO. 
acid,  at  least  in  reference  to  the  characteristic  precipitation  with 
persalts  of  iron  ;  and  the  possibility  of  obtaining  this  reaction  with 
various  kinds  of  kino,  tormentilla,  and  other  plants,  induced  Hen- 
nig  not  only  to  give  up  the  opinion  that  coccotannic  acid  is  a  defi- 
nite substance,  but  likewise  to  regard  the  different  kinds  of  tannic 
acid,  which  precipitate  persalts  of  iron  green  or  grey,  and  are  ad- 
mitted by  Chemists  to  be  in  almost  every  case  distinct  substances, 
as  intimate  mixtures  of  tannic  acid,  which  gives  a  blue  precipitate 
with  persalts  of  iron,  and  some  modifying  substance,  such  as  a  yel- 
low or  red  coloring  matter.  He  found,  however,  that  the  tannic 
acid  from  kino  differed  from  that  of  the  oak  in  two  particulars,  viz., 
the  solubility  in  ether  and  the  reaction  with  potassio-tartrate  of 
antimony  ;  but  he  considers  that  the  minute  and  probably  inappre- 
ciable quantity  of  kinoic  acid  mixed  with  the  tannic  acid  might  be 
sufficient  to  account  for  these  discrepancies. 
The  red  substance  which  Hennig  calls  kinoic  acid  corresponds 
with  the  coloring  matters  associated  with  tannic  acid  in  elm  bark, 
catechu,  cinchona  bark,  coffee,  &c,  and  cannot,  in  kino  at  least, 
be  regarded  as  a  product  of  the  oxidation  of  tannic  acid,  but  is 
probably  the  derivative  of  a  colorless  substance,  for,  according  to 
Pereira,  the  fresh  juice  of  the  kino-tree  has  but  a  faint  reddish 
tint. 
This  red  substance  is  more  readily  soluble  in  alcohol  than  in 
cold  water,  and  to  it  the  alcoholic  solution  owes  not  only  its  in- 
tense red  color  but  likewise  its  acid  reaction.  It  gives  a  yellow- 
ish brown  precipitate  with  perchloride  of  iron,  and  a  brownish  red 
one  with  acetate  of  lead.  It  partly  separates  from  the  hot  aqueous 
solution  on  cooling.  From  these  characters  many  who  have  pre- 
viously examined  this  substance  inferred  that  it  was  a  resin,  an 
opinion  which  Mohr  opposes.  A.  W.  Buchner  states  that  he  has 
detected  catechine  in  kino,  and  ascribes  to  it  the  production  of  a 
green  precipitate  with  persalts  of  iron.  Hennig,  however,  expresses 
his  conviction  that  catechin  is  not  present  in  true  kino,  and  is  only 
a  constituent  of  those  drugs  which  are  varieties  of  catechu,  al- 
though frequently  confounded  with  kino,  viz.,  Uncaria  or  Nauclea 
Gambir,  the  product  of  Erythina  monosperma. 
The  behavior  of  this  red  coloring  matter  towards  the  tannic  acid 
is  remarkable,  for  it  not  only  adheres  to  it  with  obstinacy,  perhaps 
holding  it,  together  with  the  pectin,  for  some  time  in  solution,  but 
