Am.  Jour.  Pharm. 
Dec,  1887. 
Chemical  Notes  on  Tea. 
631 
of  about  43  grains  to  3J  fluid  ounces  of  water.  The  infusion  is 
then  poured  off  from  the  leaves  into  a  cup  and  the  value  of  the  tea  es- 
timated by  its  taste.  In  this  operation  the  soluble  constituents  of  the 
leaves  are  only  partially  extracted,  and  while  more  perfect  exhaustion 
of  the  leaves,  will  give  about  35  per  cent,  of  extract,  the  amount  taken 
out  in  the  ordinary  broker's  method  of  testing  does  not  amount  to  more 
than  20  per  cent,  on  the  average.  Hence  it  is  evident  that  attempts 
to  value  tea  on  the  basis  of  the  total  amount  of  extract  obtainable  by 
treatment  with  boiling  water  must  be  entirely  fallacious  and  useless  for 
any  practical  purpose.  In  respect  to  the  amounts  of  extract  thus  ob- 
tainable from  tea  of  different  qualities,  there  is  not  in  reality  any 
such  difference  as  would  afford  indications  of  the  actual  differences  in 
value.  Peligot  and  others  have  made  determinations  of  this  kind, 
showing  that  different  kinds  of  black  tea  yield  from  24  to  47  per  cent, 
of  extract,  or  on  the  average  34  to  40  per  cent.,  but  these  data  have 
little  practical  value.  It  is  indeed  not  by  the  perfect  extraction  of 
tea  that  its  value  can  be  estimated.  This  must  be  sought  for  within 
the  limits  of  extraction  which  obtain  in  the  ordinary  methods  of  us- 
ing tea,  as  is  the  case  in  the  broker's  method  of  testing,  which  fairly 
represents  ordinary  practice  in  the  use  of  tea,  though  the  infusion  is 
then  made  stronger  than  it  is  generally  drunk. 
To  obtain  some  idea  of  the  extent  to  which  the  constituents  of  tea 
are  extracted  under  these  ordinary  conditions  we  have  made  analyses 
of  the  infusion  thus  prepared,  and  have  ascertained  as  a  general  re- 
sult that  the  20  per  cent,  of  extract  taken  out  by  the  infusion  will 
contain  about  one-half  of  the  theine  present  in  the  tea  used.  An  ordi- 
nary breakfast  cup  of  equally  strong  tea  infusion,  measuring  about 
eight  ounces,  would  therefore  contain  two  grains  of  theine,  or  there- 
abouts. The  rest  of  the  theine  is  left  in  the  spent  leaves,  and  it  re- 
quires repeated  treatment  with  boiling  water  to  extract  the  whole 
quantity.  This  is  no  doubt  one  of  the  reasons  why  the  amount  of 
theine  in  tea  has  been  underestimated  in  so  many  instances,  since  ex- 
perimenters have  operated  upon  a  water  extract  for  its  determination. 
In  one  instance  we  found  that  the  residual  leaves  of  tea  which  had 
been  used  in  the  customary  manner  contained  as  much  as  1*7  per 
cent,  of  theine,  and  in  another  case  leaves  exhausted  as  far  as  practica- 
ble by  percolating  with  boiling  water  still  contained  as  much  as  0*13 
per  cent*,  calculated  on  the  original  tea. — Phar.  Jour,  and  Trans., 
November  19,  pp.  4i7-419. 
