.302  Detection  of  Extracted  Tea.  {Amju°nUe'-if9h3arm' 
DETECTION  OF  EXTRACTED  TEA. 
By  W.  A.  Tichomirow. 
The  author  has  made  an  examination  of  such  tea  as  is  used  for 
the  falsification  of  genuine  tea.  If  dry  extracted  tea  is  covered 
with  a  cold,  saturated  solution  of  copper  acetate,  the  blue  color  of 
the  liquid  remains  unchanged  for  months.  With  dry  fresh  tea  (not 
extracted),  the  original  blue  color  of  the  liquid  is  found  on  the 
second  day  to  have  been  changed  into  a  greenish  blue,  and  subse- 
quently to  a  pure  green.  The  leaflets  of  the  fresh  (not  extracted 
tea),  remain  strongly  contracted  and  rolled  up  even  after  steeping 
in  the  water  for  weeks,  whilst  tea  which  has  been  previously 
extracted  unrolls  perfectly  without  any  previous  immersion  in 
water. 
The  characteristic  distinction  between  extracted  and  fresh  tea  is 
shown  by  the  idioblasts.  If  microscopic  sections  of  leaves  which 
have  been  steeped  for  from  I  to  4  days  in  a  cold  saturated  solution 
of  copper  acetate  are  touched  with  a  drop  of  the  "liquor  ferri 
acetici  "  of  the  Russian  Pharmacopoeia  (specific  gravity  1*134  to 
1-138),  and  examined  under  the  microscope,  all  the  histological 
elements  which  contain  tannin  have  taken  a  deep,  black-blue  color. 
The  tannins  are  fixed  in  their  normal  places  by  the  previous  treat- 
ment with  copper  acetate. 
In  leaves  which  have  been  previously  extracted,  the  cell  walls 
have  been  previously  permeated  by  the  tannin  dissolved  in  water, 
whilst  in  fresh  tea  they  remain  colorless,  because  the  tannins  are 
found  normally  not  in  the  idioblasts,  but  in  the  surrounding  paren- 
chyma cells.  The  shrivelling  and  the  inability  to  unroll  in  water 
the  tea-leaves  which  have  not  been  previously  extracted  with  hot 
water  must  depend  on  the  formation  of  a  dense,  solid  copper  tannate, 
insoluble  in  water.  It  is  a  kind  of  tannin  which  prevents  the  tur- 
gescence  of  the  tissues. 
E.  Hanausek  (Zeit.  f.  N ahrungsmittel-  Unterszichung)  detected  the 
appearance  of  a  green  color  also  in  extracted  tea,  and  in  his  experi- 
ments the  idioblasts  did  not  show  sharply  and  consistently  the 
expected  microchemical  reactions,  probably  in  consequence  of  the 
complete  exhaustion  of  the  leaves.  Hanausek's  further  experi- 
ments had  the  purpose  of  determining  the  refractive  index  of  the 
infusion  of  tea  as  a  distinction  between  extracted  and  recent  tea. 
