'm'MJa°yUri9i4arm"}        Chemistry  of  a  Cup  of  Coffee.  219 
the  view  being  that  the  secret  of  good  coffee  is  to  make  it  strong. 
This,  of  course,  is  an  entirely  aesthetic  demand,  which  may  likely 
enough  be  opposed  to  physiological  morality. 
The  Strength  of  Cold  Water  Extracts  of  Coffee  Compared 
with  Boiling  Water  Extracts. 
The  fact  that  the  caffeine  in  coffee  is  completely  soluble  in  cold 
water  suggested  making  a  comparison  as  to  the  composition  of  the 
cold  and  hot  water  infusions  in  regard  to  other  constituents.  For 
this  purpose  several  types  of  coffee  were  chosen,  all  of  which  reached 
this  country  through  Costa  Rica.  As  will  be  seen  from  the  accom- 
panying table,  the  varieties  examined  were  as  follows :  Raw  {i.e., 
unroasted)  Costa  Rica,  common  quality;  raw  Costa  Rica,  finest 
quality ;  pale  roasted  Costa  Rica,  common  quality ;  pale  roasted  Costa 
Rica,  finest  quality ;  high  roasted  Costa  Rica,  common  quality ;  and 
high  roasted  Costa  Rica,  finest  quality.  The  results  are  instructive, 
and  we  may  proceed  to  consider  the  differences  in  composition  of 
the  infusions,  both  cold  and  hot,  shown  where  raw,  pale  roasted, 
and  high  roasted  coffee  are  employed,  and  the  relationships,  if  any, 
of  these  differences  to  the  discrimination  supplied  by  the  expert 
taster,  who  describes  a  particular  coffee  as,  in  his  own  words,  "  com- 
mon "  or  "  finest." 
It  is  a  somewhat  remarkable  fact  that  cold  water  extracts  from 
coffee  the  same  weight  of  materials  as  boiling  water,  but  it  must 
be  admitted  that  the  former  infusion  is  somewhat  less  palatable 
than  the  latter.  Chemically,  however,  there  is  little  difference  be- 
tween them,  and  we  may  presume  that  physiologically  a  cold  water 
extract  of  coffee  will  be  much  the  same  as  a  hot  water  infusion,  leav- 
ing out  aesthetic  considerations,  although  these,  of  course,  are  exceed- 
ingly important,  from  all  dietetic  aspects.  It  is  probable  that  cold 
water  fails  to  extract  certain  oily  bodies  or  fats  which  contribute 
attractive  taste  and  aroma.  The  total  extract  is  frequently  higher 
in  cold  than  in  hot  water.  And  not  only  is  caffeine  extracted  from 
coffee  equally  well  by  cold  and  hot  water,  but  this  is  true  of  the 
mineral  salts  and  of  the  peculiar  acid  known  as  caffetannic  acid,  the 
acid  which  corresponds  to  the  tannin  of  tea.  In  regard  to  the  pro- 
portion of  materials  soluble  in  cold  water  coffee  shows  an  entirely 
different  result  to  tea,  inasmuch  as  while  coffee  yields  about  25  per 
cent,  of  its  weight  to  cold  water  (an  amount  which  is  not  increased 
