£76 
VARIETIES. 
We  have  observed  a  property  of  caffeic  acid  which  facilitates  the  detec- 
tion of  that  substance,  and  consequently  of  coffee,  in  a  mixture.  Caffeic 
acid  appears  to  be  analogous  to  kinic  acid,  the  acid  of  cinchona  barks,  for 
it  yields  kinone  when  oxidated  by  means  of  sulphuric  acid  and  binoxide  of 
manganese.  To  observe  this  property,  the  coffee  is  boiled  with  water  and  a 
little  slaked  lime,  the  infusion  filtered,  and  evaporated  down  to  the  consist- 
ence of  a  syrup.  The  syrupy  liquid  is  then  mixed  in  a  retort  with  four 
times  its  weight  of  binoxide  of  manganese,  and  one  part  of  oil  of  vitrol 
diluted  with  an  equal  bulk  of  water.  Sufficient  heat  is  produced  by  the 
action  of  sulphuric  acid  upon  the  other  materials,  to  bring  over  the  greater 
portion  of  the  kinone,  and  the  lamp  need  not  be  applied  till  towards  the  close 
of  the  operation.  The  distillate  consists  of  yellow  crystals  of  kinone,  which 
usually  coat  the  neck  and  sides  of  the  retort,  and  a  bright  yellow  liquid, 
which  is  a  saturated  aqueous  solution  of  kinone,  with  a  considerable  quan- 
tity of  formic  acid.  Kinone  is  easily  discernible  by  its  volatility  and  pecu- 
liarly acrid  odor,  which  greatly  resembles  that  of  chlorine.  The  solution 
of  kinone  gives  with  ammonia  a  sepia-black  color,  and  becomes  reddish- 
brown  with  hydrosulphuric  acid.  It  is  decolorized  by  sulphurous  acid.  The 
beautiful  green  hydrokinone  is  obtained  by  exactly  neutralizing  the  solution 
of  the  yellow  kinone  with  sulphurous  acid,  great  care  being  taken  not  to 
introduce  the  latter  in  excess. 
The  peculiar  acid  of  Paraguay  tea  agrees  with  cafieic  acid  (to  which  it  is 
no  doubt  related)  in  yielding  kinone  to  similar  oxidizing  agencies  ;  so  does 
the  acid  of  the  leaves  of  common  holly  (Ilex  aquifolium)  tea,  and  the  whole 
of  the  cinchona  tribe. 
The  -prune  tribe  of  plants,  including  the  sloe,  cherry,  laurel,  &c,  the  seeds 
of  which  yield  prussic  acid,  all  contain  amygdalin,  or  some  similar  principle. 
Now  all  of  these,  when  oxidized  in  the  same  manner  as  the  former  class, 
yield  oil  of  bitter  almonds,  and  so  can  be  recognized. 
The  willow  and  poplar  tribe,  on  the  other  hand,  yield  oil  of  Spirea  ulmaria 
(salieylous  acid),  a  very  characteristic  substance. 
The  tests  for  kinone  can  be  applied  in  a  few  minutes,  and  they  are  suffi- 
cient to  indicate  the  presence  often  or  twelve  per  cent,  of  coffee  in  a  mix- 
ture. 
12.  The  root  of  chicory  presents  no  feature  of  a  marked  nature,  beyond 
its  large  proportion  of  sugar  and  the  composition  of  its  ash,  which  have  both 
been  sufficiently  adverted  to.  The  proportion  of  fat  naturally  in  the  root, 
is  quite  insignificant.  In  an  infusion  of  the  fresh  undried  root,  neutral 
acetate  of  lead  appears  to  throw  down  the  whole  acids  of  chicory,  and  the 
subacetate  of  lead  produces  no  further  precipitate  in  the  liquid.  But  the 
root  appears  to  undergo  a  considerable  modification  by  being  dried  at  a 
temperature  not  exceeding  212°.  Its  infusion  now  gives  a  second  precipi- 
tate with  subacetate  of  lead  following  the  neutral  acetate.  Both  of  these 
precipitates  can  be  well  enough  washed  ;  but  when  the  attempt  was  made 
to  decompose  either  of  them  by  means  of  hydrosulphuric  acid,  a  mucila- 
