506 
Extract  of  Guarana,  etc. 
(  Am.  Jour.  Pharm. 
t    Nov.  1, 1874. 
Any  one  who  has  never  tried  this  plan  will  be  surprised  at  its 
advantages,  and  will  sometimes  be  astonished  at  what  the  sieve  will 
remove  from  powders  that  were  apparently  perfectly  uniform  and 
pure.  Of  course,  the  sieve  employed  for  this  purpose  must  not  be 
too  fine.  For  powders  ranging  from  No.  40  to  80  about  a  No.  20 
sieve  will  answer,  and  for  coarser  powders  a  coarser  sieve  in  propor- 
tion. 
I  would  recommend  to  inexperienced  operators  the  plan  I  have 
adopted  in  percolating  powdered  substances  with  which  I  am  not 
familiar,  or  which  I  have  not  treated  for  some  time,  which  is  to  first 
moisten  only  a  small  portion  of  the  powder,  and  pack  it  according  to 
your  best  judgment,  pour  upon  it  a  small  portion  of  the  menstruum, 
just  sufficient  to  see  how  it  enters  the  powder.  The  unabsorbed  por- 
tion should  then  be  returned  to  the  remainder  of  the  menstruum  and 
the  moistened  powder  should  be  returned  to  the  remainder  of  the 
powder  and  thoroughly  mixed  with  it  before  the  addition  of  more 
menstruum.  By  this  means  we  can  generally  form  a  correct 
idea  how  the  whole  of  the  powder  should  be  packed.  When  operating 
with  a  pound  or  more  of  material,  I  have  often  made  several  of  these 
preliminary  trials  with  small  portions  of  the  powder.  It  is  im- 
portant, however,  not  to  take  too  much  of  the  powder  for  these 
experimental  trials,  or  the  moisture  absorbed  by  it  may  make  the 
reserved  portion  of  the  powder,  when  mixed  with  it,  too  moist  for 
correct  packing.  This  simple  expedient  may  often  save  the  operator 
much  vexation,  and  even  entire  failure,  in  important  operations  in 
making  fluid  extracts. 
It  may  be  well  for  me,  in  this  connection,  to  say  a  word  also  in 
regard  to  the  manner  of  moistening  powders  preparatory  to  percola- 
tion, and  of  packing  them  when  moistened. 
Many  pharmacists  are  in  the  habit  of  using  a  stick  or  other  instru- 
ment with  which  to  stir  the  powder  as  the  menstruum  is  added,  as 
though  contact  with  the  substance  would  prove  fatal.  By  this  dainty 
method  of  manipulation,  powders  are  often  very  irregularly  and  im- 
perfectly moistened,  and  a  much  longer  time  is  consumed  in  the 
operation  than  would  otherwise  be  required,  resulting,  in  hot  weather, 
in  a  considerable  loss  of  menstruum  by  evaporation.  In  this  way, 
too,  the  powder  is  often  left  full  of  lumps  or  masses,  with  some  por- 
tions too  moist,  others  too  dry,  and  the  whole  in  a  bad  condition  for 
packing. 
