AmjJa°nu;'if9|araj  }        Examination  of  Chinese  Tea.  49 
water ;  and  (5)  an  indigo-carmine  solution  prepared  by  mixing  50 
grams  of  pure  indigo-carmine  paste  with  water,  adding  50  grams  of 
sulphuric  acid  and  a  litre  of  water,  filtering,  and  diluting  until  25  cc. 
of  the  solution  require  20  cc.  of  the  permanganate  for  oxidation. 
The  tea  solution  (10  grams  in  the  litre)  is  prepared  as  already 
described,  and  of  this  40  cc.  is  diluted  with  500  cc.  of  water,  treated 
with  25  cc.  of  the  indigo-carmine  solution  and  25  cc.  of  dilute  sul- 
phuric acid,  and  titrated  with  permanganate  until  the  yellow  color 
becomes  evident.  The  manner  in  which  the  permanganate  is  added 
is  of  considerable  importance,  and  the  author  states  that  in  the 
titration  of  the  indigo-carmine  solution,  18  cc.  of  the  permanganate 
is  added  at  the  rate  of  2-3  drops  per  second,  and  the  remainder  at 
the  rate  of  1  drop  per  second,  and  that  in  the  titration  of  the  tea 
with  indigo-carmine,  23  cc.  of  the  permanganate  is  run  in  first  of  all,, 
then  2-3  drops  per  second  is  added,  and  finally  only  1  drop  per 
second  until  the  reaction  is  completed.  If  more  than  38  cc,  of  per- 
manganate is  required  in  the  latter  titration,  a  smaller  quantity  of 
the  tea  solution  should  be  taken  for  the  analysis.  The  amount  of 
the  fermentation  product  is  then  estimated.  For  this  purpose,  80 
cc.  of  the  tea  solution  is  mixed  with  20  cc.  of  baryta-water,  filtered, 
and  50  cc.  of  the  filtrate  corresponding  with  i/25th  of  the  tea 
extract  is  diluted  with  500  cc.  water,  mixed  with  25  cc.  of  dilute 
sulphuric  acid,  then  with  25  cc.  of  the  indigo-carmine  solution,  and 
titrated  with  permanganate,  18  cc.  of  the  solution  being  run  in,  first 
of  all,  then  2-3  drops  per  second  added,  and  finally  1  drop  per  second 
until  the  reaction  is  ended.  The  amount  of  permanganate  employed, 
less  that  required  for  the  oxidation  of  the  indigo-carmine,  indicates 
the  amount  of  decomposition  products  of  tannin,  or,  more  correctly, 
the  degree  of  fermentation  which  the  tea-leaves  have  undergone. 
The  percentage  of  tannin  and  of  the  fermentation  product  is  calcu- 
lated by  multiplying  the  weight  of  oxalic  acid  equivalent  to  the 
number  of  cc.  of  permanganate  employed  in  the  oxidation,  by  31-3, 
since  63  grams  of  oxalic  acid,  according  to  the  author's  experiments, 
correspond  with  31-3  grams  of  tannin,  and  not  with  41-2  grams  as 
stated  by  Neubauer. 
With  regard  to  the  comparative  values  of  teas,  the  author  states 
that  the  higher  the  proportion  of  theine  to  the  total  amount  of 
tannin  and  fermentation  products,  the  more  valuable  is  the  tea. 
The  analyses  of  teas  of  the  first  crop  of  1890  are  quoted  in  the  paper, 
