Am.  Jour.  Pharm. 
May,  1914. 
Chemistry  of  a  Cup  of  Coffee. 
221 
infusion  of  raw  coffee  (unroasted)  the  caffetannic  acid  amounts  to 
9.60  per  cent.,  it  is  in  the  pale  roasted  6.60  per  cent.,  while  by 
further  roasting,  as  in  the  "  high  roasted,"  it  is  reduced  in  the 
infusion  from  3.63  to  3.90  per  cent.  What  part  cafTetannic  acid  ex- 
actly plays  as  a  dietetic  constituent  of  coffee  it  is  difficult  to  say, 
but  if  it  should  prove  to  be  an  undesirable  element,  then  the  high 
roasted  coffees  are  least  open  to  objection  on  this  account.  It  may 
be  noticed  also  that  the  raw  coffee  yields  a  greater  percentage  of 
soluble  constituents  to  both  cold  and  hot  water  than  high  roasted 
coffee,  the  pale  roasted  coffee  showing  intermediate  results.  Roast- 
ing, amongst  other  things,  has,  therefore,  the  effect  probably  of 
rendering  certain  bodies  insoluble — e.g.,  albumins — while  the  slight 
burning  effect  upon  carbohydrates  would  produce  possibly  some  free 
and  of  course  insoluble  carbon. 
Quality  of  Coffee  in  Relation  to  Chemical  Composition. 
From  the  results  recorded  in  the  table  it  will  be  seen  that  no 
definite  relation  cambe  traced  between  the  aesthetic  quality  of  coffees, 
classed  respectively  as  "  common  "  and  "  finest,"  and  the  chemical 
composition  of  the  infusions  which  they  yield.  It  may  be  noted  that 
there  is  no  important  difference  in  the  amount  of  the  drug  caffeine 
when  the  common  and  finest  varieties  are  examined.  It  is  probable 
that  the  aesthetic  values — flavour,  body,  aroma,  and  so  forth — are  re- 
lated in  some  way  to  the  amounts  of  oil  bases  or  aromatic  principles 
present,  and  these  are  in  any  case  minute.  Whether  they  are  present 
in  appreciable  quantity  or  not  doubtless  depends  upon  the  care  spent 
upon  the  roasting  process.  At  any  rate,  it  is  conceivable  that  a  point 
in  the  roasting  process  could  be  reached  which  would  deprive  the 
coffee  of  all  attractive  flavour,  while  it  is  certain  that  the  infusion  of 
the  raw  unroasted  berry  is  not  fit  to  drink  on  account  of  its  un- 
pleasant taste.  Recently  it  has  been  announced  on  more  than  one 
occasion  that  pyridin  is  an  important  constituent  of  coffee.  We  have 
certainly  found  it  present,  but  not  in  sufficient  quantities  to  estimate. 
It  is  rather  a  curious  fact  that  some  authorities  mention  that  coffee 
often  relieves  asthma,  while  pyridin  is  described  as  "  useful  in  the 
treatment  of  asthma  "  and  "  beneficial  in  cardiac  dyspnoea,  emphy- 
sema, and  angina  pectoris,"  and,  finally,  that  "  it  is  probably  the 
relieving  agent  of  various  cigarettes  and  powders  smoked  or  burnt 
for  asthma  and  whooping-cough."    Another  constituent  of  coffee 
