220 
Chemistry  of  a  Cup  of  Coffee.  { 
Am.  Jour.  Pharm. 
May,  1914. 
when  hot  water  is  used)  tea  yields  only  12  per  cent,  of  its  weight  to 
cold  water,  which  is  increased  to  25  per  cent,  when  the  infusion  is 
made  with  hot  water.  Again,  cold  water  extracts  from  tea  only  17.5 
per  cent,  of  its  total  caffeine,  while  from  coffee  it  extracts  the  whole. 
Similarly,  cold  water  extracts  from  tea  13  per  cent,  of  its  total  tan- 
nin, while  coffee  under  the  same  treatment  yields  practically  the 
whole  of  its  caffetannic  acid. 
The  Effect  of  Roasting. 
An  infusion  of  green  or  unroasted  coffee  is  singularly  nasty  to 
the  palate,  and  it  follows  that  the  roasting  process  renders  coffee 
the  palatable  article  that  it  is.  The  chemistry  of  roasting  amounts 
largely  to  a  caramelisation  process,  during  which  certain  oils  and 
aromatic  principles  are  formed  as  products  of  a  mild  destructive  dis- 
tillation. Curiously  enough,  there  is  little  loss  of  caffeine  in  this 
process,  as  our  results  show,  which  is  remarkable  in  view  of  the 
fact  that  caffeine  sublimes  at  high  temperatures.  There  are  two 
degrees  of  roasting  adopted — viz.,  pale  roasting  and  high  roasting. 
The  important  chemical  effect  of  roasting,  according  to  our  analyses, 
is  to  diminish  considerably  the  amount  of  caffetannic  acid.  If  the 
figures  in  the  table  be  consulted  it  will  be  seen  that  while  in  an 
The  Analysis  of  Hot  and  Cold  Infusions  of  Coffee. 
Constituent. 
Raw  Costa  Rica 
(common). 
Raw  Costa  Rica 
(finest). 
Pale  roasted  Costa 
Rica  (common). 
Hot 
infusion. 
Cold 
infusion. 
Hot 
infusion. 
Cold 
infusion. 
Hot 
infusion. 
Cold 
infusion. 
Total  extract  
Ash  of  extract  
Caffetannic  acid  
29.16 
4.16 
9.60 
1. 00 
30.83 
3-88 
8.63 
1-33 
29.60 
4.00 
9.66 
1. 21 
3i.5o 
3-88 
7.83 
1.56 
25-33 
4.16 
6.10 
1. 11 
24.00 
5-66 
5.8o 
1. 11 
Constituent. 
Pale  roasted  Costa 
Rica  (finest). 
High  roasted  Costa 
Rica  (common). 
High  roasted  Costa 
Rica  (finest). 
Hot 
infusion 
Cold 
infusion. 
Hot 
infusion. 
m  Cold 
infusion. 
Hot 
infusion 
Cold 
infusion. 
23.SO 
25.66 
24.30 
24.00 
25.60 
23.00 
3-50 
4-50 
4.66 
4.00 
4.00 
4-50 
Caffetannic  acid  
6.60 
5-90 
3-90 
3.16 
363 
3.87 
Total  caffeine  
1. os 
1.06 
1.23 
1. 11 
1.05 
1.20 
