456  Micro-Chemistry  of  Tea  Leaves.     { AmseJp°u,r ™*Tm' 
crystalline  body,  but  only  a  saccharide  resembling  in  every  respect  the 
last. 
On  fusing  with  potassium  hydrate,  the  oak  tannin  yields,  amongst 
other  products,  butyric  acid  amongst  the  volatile  products,  and  proto- 
catechuic  acid  from  the  residue.  Willow  tannin,  similarly  treated,, 
yielded  acetic  and  butyric  acid  amongst  the  volatile  products,  whilst 
the  residue  in  the  retort  contained  a  body  whose  identity  could  not  be 
satisfactorily  made  out.  Elm  tannin,  treated  in  the  same  manner*, 
yielded  acetic  and  butyric  acids  among  the  volatile  products,  and  oxy- 
phenic  acid    in  the  residue. — Jour.   Chem.  June,    1877,  from 
Arch.  Phar.  [3],  ix,  210 — 248. 
MICRO-CHEMISTRY  as  APPLIED  to  the  IDENTIFICA- 
TION of  TEA  LEAVES,  and  a  NEW  METHOD  for  the 
ESTIMATION  of  THEINA. 
By  A.  Wynter  Blyth,  F.C.S. 
I  have  been  lately  examining  tea  leaves,  with  a  view  of  obtaining 
some  chemical  test,  either  peculiar  to  them  or,  at  all  events,  restricted 
to  the  thein-producing  plants.  The  result  of  my  experiments  has  been 
the  establishment  of  a  process  of  great  simplicity  which  will  enable 
any  one  in  a  few  minutes  to  pronounce  whether  the  merest  fragment 
of  a  plant  belongs  to  the  thein  class  or  not.  The  procedure  is  based 
upon  the  well-ascertained  fact  that  the  alkaloid  already  alluded  to  is  dis- 
tributed in  the  woody  tissue,  the  bark,  the  stem,  the  leaf,  the  flower,, 
in  short,  in  all  parts  of  a  thein  plant,  and  this  is  the  more  especially 
true  in  the  case  of  the  various  species  of  Tbea.  Now,  this  thein  has 
some  very  characteristic  properties  j  the  most  useful  of  these  for  my 
present  purpose  are,  that  it  commences  to  sublime  at  the  comparatively 
low  temperature  of  1010  C.  ;  that  it  sublimes  from  organic  substances 
in  a  perfectly  pure  crystalline  state  ;  that  the  crystals  have  a  very  defi- 
nite, easily  recognizable  form,  and  that  a  one-thousandth  of  a  milligram 
is  distinctly  seen  aud  may  be  identified  by  the  aid  of  the  microscope. 
The  details  of  the  process  I  use  are  as  follows : 
(1.)  The  leaf  or  fragment,  if  it  is  desired  to  examine  it  subsequently 
by  the  microscope,  is  boiled  in  a  very  small  quantity  of  water,  say  a 
cubic  centimeter,  and  the  little  decoction  is  transferred  to  a  watch  glass,, 
a  minute  quantity  of  calcined  magnesia  added,  and  the  whole  evapo- 
