252 
ON  THE  DRIED  COFFEE-LEAF  OF  SUMATRA. 
with  a  considerable  quantity  of  formic  acid.  Kinone  is  easily 
discernible  by  its  volatility  and  peculiarly  acrid  odor,  which 
greatly  resembles  that  of  chlorine.  The  solution  of  kinone  gives 
with  ammonia  a  sepia  black  color.  It  is  decolorized  by  sulphur- 
ous acid.  The  beautiful  green  hydrokinone  is  obtained  by 
exactly  neutralizing  the  solution  of  the  yellow  kinone  with  sul- 
phurous acid,  great  care  being  taken  not  to  introduce  the  latter 
in  excess. 
"  The  peculiar  acid  in  Paraguay  tea  agrees  with  caffeic  acid, 
to  which  it  is  no  doubt  related,  in  yielding  kinone  to  similar 
oxidizing  agencies  ;  so  does  the  acid  of  the  leaves  of  the  common 
holly,  Ilex  aquifoUum,  and  the  whole  of  the  cinchona  tribe." 
When  coffee-leaves  are  boiled  with  a  considerable  quantity  of 
water,  and  a  slight  excess  of  milk  of  lime,  the  dark  brown  strongly 
alkaline  liquor  is  cautiously  evaporated  to  dryness,  and  then 
treated  in  the  way  already  described,  with  three  times  its  weight 
of  black  oxide  of  manganese  and  one  part  of  sulphuric  acid, 
diluted  with  its  own  bulk  of  water,  a  much  larger  quantity  of 
crystals  of  kinone  are  obtained  than  can  be  procured  from  an 
equal  weight  of  the  coffee-bean.  This  clearly  shows  that  the 
leaves  are  richer  in  caffeic  acid  than  the  beans. 
Kinone  may,  I  find,  be  obtained  in  small  quantity  by  a  similar 
process  from  a  great  number  of  our  commonest  plants.  Thus  I 
also  obtained  indications  of  kinone  from  the  leaves  and  branches 
of  the  privet,  Ligustrum  vulgare  ;  from  the  common  ivy,  Hedera 
helix,  from  the  Quercus  Ilex,  the  evergreen  oak  ot  our  gardens 
and  shrubberies,  a  native  of  Turkey;  from  the  Quercus  robur, 
the  common  British  oak ;  from  the  Ulmus  campestris,  the  com- 
mon small-leaved  elm ;  from  the  ash,  Fraxinus  excelsior ;  and 
from  the  bush-tea  of  the  Cape  of  Good  Hope,  the  Cyclopia  lati- 
folia  of  De  Candolle,  a  plant  of  the  natural  order  Leguminosas. 
From  numerous  plants  which  I  tried,  I  could  not  obtain  a  trace 
of  kinone.  This  was  the  case  among  others  with  laburnum, 
Cytisus  laburnum,  with  tobacco,  with  Primus  spinosa,  the  sloe, 
and  others  too  numerous  to  mention. 
The  kinone  was  only  obtained  in  crystals  from  the  coffee-bean, 
from  the  coffee-leaf,  and  from  the  holly,  Ilex  aquifoUum,  In  all 
the  other  cases,  its  existence  was  detected  by  the  deep  yellow 
liquid  which  distilled  over  at  a  comparatively  low  temperature, 
and  which  yielded  the  dark  humus-like  coloration  with  ammonia, 
