374 
VARIETIES. 
acid,  when  strongly  heated  in  an  open  vessel,  emits  the  peculiar  odor  of 
roasted  coffee  ;  but  the  acid  from  Paraguay  tea  emits  a  perfectly  different 
odor  when  similarly  treated. 
The  sugar  of  coffee  may  be  inferred  to  exist  in  a  peculiar  condition,  as 
was  before  hinted,  from  the  fact  that  when  the  coffee  is  roasted,  none  of  its 
sugar  appears  to  be  converted  into  grape-sugar,  as  it  does  not  affect  Trom- 
mels test ;  while,  when  seven  grains  of  cane-sugar  were  added  to  100  grains 
of  coffee,  and  the  whole  roasted  in  the  usual  way,  abundant  indications  of 
grape-sugar  were  obtained  by  the  same  test. 
M.  Payen  gives  the  proportional  quantities  of  the  different  substances 
which  he  finds  in  raw  coffee  as  follows : — 
Cellular  tissue    .....  34.000 
Hygroscopic  water  ....  12  000 
Fats  10.  to  13.000 
Starch,  sugar,  dextrin,  and 
vegetable  acids    ....  15.000 
Legumin   1.000 
Chlorogenate  of  potash  and 
caffeine   3.500 
Nitrogenous  portion    .    .    .  3.000 
Free  caffeine   0.800 
Thick  insoluble  ethereal  oil  .  0.001 
Aromatic  oil   0.002 
Mineral  constituents ;  potash, 
lime,  magnesia,  phosphorus, 
sulphur,  silica,  and  traces 
of  chlorine  6.697 
Payen's  chlorogenic  acid  is  the  same  as  the  caffeic  acid  of  Kochleder  and 
Pfaff.  Payen  believed  that  he  had  obtained  from  coffee  a  crystalline  double 
salt  of  this  acid,  containing  potash  and  caffeine  ;  but  this  observation  has 
not  been  confirmed. 
The  proportion  of  fat  in  the  coffee-bean  is  remarkably  high,  being  gener- 
ally stated  at  ten  or  about  ten  per  cent.  We  found  at  least  8.9  per  cent,  of 
fat  readily  extracted  by  ether.  In  chicory  the  proportion  of  natural  fat  is 
scarcely  appreciable  ;  but  it  is  brought  up  by  the  fat  added  in  the  process 
of  roasting  the  chicory. 
10.  Some  uncertainty  existing  respecting  the  proportion  of  the  active  prin- 
ciple, caffeine,  in  coffee,  the  point  was  particularly  inquired  into.  The  fol- 
lowing process  was  adopted : — The  raw  coffee  was  ground  fine,  having  been 
previously  well  dried  at  212°  to  facilitate  that  operation.  A  decoction  was 
then  made  of  1000  grains,  by  the  repeated  application  of  boiling  water,  so 
as  to  exhaust  the  coffee  of  all  soluble  matter.  The  solution  was  concen- 
trated a  little  by  evaporation.  The  acid  of  the  coffee,  and  certain  other 
substances,  were  now  entirely  precipitated  by  the  addition,  first,  of  the  neu- 
tral acetate  of  lead,  and  then  of  the  subacetate  of  lead.  These  insoluble 
matters  were  removed  from  the  liquid  by  filtration.  The  excess  of  lead  in 
solution  was  then  thrown  down  by  means  of  hydrosulphuric  acid. 
The  liquid,  after  this  preparation,  was  evaporated  to  dryness,  and  the  dry 
matter  left  was  exhausted  by  moans  of  strong  spirit  of  wine  (sp.  gr.  0.840). 
The  alcoholic  solution  was  concentrated  by  evaporation,  and  allowed  to 
stand  in  a  nearly  syrupy  state  for  about  ten  days,  in  order  to  crystallize. 
The  crystals,  which  ars  caffeine,  were  collected  upon  a  small  filter,  and  com- 
