AmseJp0tu,r'x37h7arni }      Micro-Chemistry  of  Tea  Leaves.  459 
A  quantity  not  less  than  one  gram  or  more  than  two  grams  of  either 
tea  or  coffee,  in  its  undried  state,  is  as  finely  powdered  as  possible,  and 
treated  in  a  flask  with  70  cc.  of  water  ;  the  flask  is  attached  to  a  reversed 
Liebig's  condenser,  and  the  liquid  boiled  for  one  hour  ;  the  decoction, 
including  the  powdered  substance,  is  transferred  to  a  porcelain  dish  ; 
about  the  same  weight  of  calcined  magnesia  as  the  substance  originally 
taken  is  added,  and  the  whole  evaporated  down  nearly  to  dryness  ;  the 
powdery  extract  is  now  transferred  to  the  iron  subliming  plate  already 
spoken  of,  and  covered  with  a  tared  glass  funnel,  the  edge  of  which 
must  be  accurately  ground,  and  the  tube  of  which  must  be  several 
inches  long.  The  substance  should  form  a  very  thin  equal  layer  within 
the  circle  of  the  funnel,  which  may  be  easily  accomplished  by  a  series 
of  gentle  taps.  The  heat  at  first  should  not  exceed  uo°  C,  then, 
when  the  substance  appears  thoroughly  dry,  it  may  be  gradually 
raised  to  2000  C,  and  towards  the  latter  stages  to  2200  C.  If 
the  heating  has  been  properly  regulated,  there  will  be  no  distilla- 
tion of  empyreumatic  products,  but  the  alkaloid  sublimes,  in  the 
cool  part  of  the  funnel,  in  a  compact  coating,  cone  shaped,  of  beau- 
tifully white  silky  crystals.  In  order  to  ascertain  when  the  sublima- 
tion is  complete,  the  tared  funnel  may  be  cooled  and  weighed  at  inter- 
vals, or  a  series  of  tared  funnels  may  be  kept  on  hand  and  changed 
until  no  more  thein  is  extracted.  The  funnel  as  well  as  the  thein,  as 
may  be  expected,  at  the  end  of  the  process  is  perfectly  dry,  and  the 
increase  of  weight  is  thein  pure  and  simple.  By  the  method  described 
I  have  made  numerous  determinations  of  thein,  and  have  afterwards 
digested  the  powder  remaining,  for  twenty-four  hours  in  ether,  but 
have  failed  to  obtain  any  crystalline  product  ;  I,  therefore,  believe  that 
the  whole  of  the  alkaloid  is  sublimed,  and  that  the  results,  with  care, 
are  accurate.  From  one  to  two  grams  may  be  considered  by  some  too 
small  a  quantity  for  an  accurate  assay,  and,  if  so,  there  is  no  reason 
why  very  much  larger  weights  should  not  be  used  ;  indeed,  the  process 
is  well  adapted  for  working  on  a  large  scale,  and  if  there  ever  should 
be  any  great  demand  for  the  alkaloid  would  probably  be  employed. 
There  is  yet  another  micro-chemical  test  which  belongs  to  pyrology, 
and  that  is  the  presence  of  manganese  in  the  ash  of  tea.  The  ash  of 
a  single  leaf  will  give  a  distinct  green  manganate  of  soda  bead,  and, 
unfortunately  for  our  purposes,  so  will  the  ash  of  a  great  many  other 
leaves;  but  since  I  have  never  found  any  tea  leaf  without  manganese, 
