33  ^  Extraction  of  Caffeina  from  Guar  ana.  { Amji?y,r;^h7arm" 
ment  the  quantitative  determination  of  the  caffeina  in  this  substance 
can  be  effected  with  the  utmost  facility. 
The  details  of  the  method  are  as  follows  :  the  powdered  guarana  is 
intimately  mixed  with  three  times  its  weight  of  finely  divided  litharge, 
and  the  mixture  boiled  in  distilled  water,  the  ebullition  being  continued 
until,  on  allowing  the  temperature  to  fall  below  the  boiling  point,  the 
insoluble  portion  is  found  to  subside  rapidly,  leaving  the  supernat- 
ant liquid  clear,  bright,  and  without  color.  The  quantity  of  distilled 
water  required  will  be  found  to  be  about  a  pint  for  every  fifteen  grams 
of  the  guarana  used  in  the  experiment,  and,  as  the  boiling  has  to  be  con- 
tinued for  several  hours  before  the  desired  and  all-essential  separation 
mentioned  above  takes  place,  water  must  be  added  from  time  to  time  to 
supply  the  place  of  that  lost  by  evaporation.  When  cool,  the  clear 
liquid  is  decanted  upon  a  filter,  and  when  it  has  passed  through,  which 
it  will  be  found  to  do  with  facility,  the  precipitate  is  to  be  transferred  to 
the  filter  and  washed  with  boiling  water,  the  washing  to  be  continued  as 
long  as  yellowish  precipitates  are  produced  with  either  phosphomolybdic 
acid  solution,  auric  or  platinic  chloride.  A  stream  of  sulphuretted 
hydrogen  gas  is  now  passed  through  the  filtrate  to  remove  the  small 
quantity  of  Jead  that  has  been  dissolved,  and  the  sulphide  thus  formed 
separated  by  filtration.  The  solution  is  evaporated  on  a  water  bath  to 
expel  the  excess  of  sulphuretted  hydrogen,  filtered  to  remove  a  trace  of 
sulphur,  finally  evaporated  to  the  crystallizing  point,  and  the  caffeina,, 
which  crystallizes  out  on  cooling,  removed  from  the  mother  liquor  and 
pressed  between  folds  of  bibulous  paper.  After  being  thus  treated  the 
crystals  will  be  found  to  be  perfectly  white.  On  diluting  the  mother 
liquor  with  distilled  water,  filtering  and  evaporating,  a  second  crop  of 
crystals  are  obtained,  which  are  also  perfectly  white,  after  being  pressed 
as  above.  The  crystals  are  now  dissolved  in  boiling  diluted  alcohol, 
filtered,  and  the  solution  set  aside  to  crystallize  by  spontaneous  evapo- 
ration. The  resulting  crystals  of  caffeina  are  perfectly  pure  and 
colorless. 
In  order  to  test  the  accuracy  of  the  process,  fourteen  grams  of 
guarana  in  an  impalpable  powder  were  treated  with  the  utmost  care,  as 
above  described.  The  extracted  caffeina,  after  drying  at  ioo°  F.  until 
the  weight  became  constant,  was  found  to  weigh  "joy  grams,  5*05 
per  cent.,  a  remarkably  close  approximation  to  the  results  of  Stenhouse> 
