Am.  Jour.  Pharm.  ) 
Nov.  1,1874.  J 
Extract  of  Guarana,  etc. 
501 
tion,  at  a  temperature  not  exceeding  120°,  until  the  whole  is  reduced 
to  the  proper  consistence. 
During  the  concentration,  in  making  this  extract,  the  liquid  should 
be  stirred  almost  constantly,  and  especially  is  this  necessary  at  the 
close  of  the  process. 
In  the  manufacture  of  all  extracts,  both  solid  and  fluid,  this  im- 
portant precaution  of  stirring  during  the  evaporation  should  be  observed 
as  it  is  by  the  neglect  of  this  that  the  products  in  such  cases  are  so 
often  injured  by  heat.  When  it  is  observed,  the  concentration  pro- 
ceeds more  rapidly  and  satisfactorily,  and  the  medicinal  virtues  of  the 
drug  under  treatment  thus  enjoy  a  comparative  immunity  from  the 
injurious  influences  of  heat. 
In  making  fluid  extracts,  when  reserved  portions  are  to  be  concen- 
trated to  a  given  point,  by  either  artificial  or  spontaneous  evaporation, 
preparatory  to  receiving  the  product  of  the  remainder  of  the  percolate, 
it  is  very  important  to  see  that  the  concentration  does  not  proceed 
too  far. 
The  evaporation  should  be  closely  watched,  and  the  moment  it  has 
reached  the  desired  point,  the  liquid  should  at  once  be  transferred 
to  a  bottle  and  tightly  corked,  to  await  the  product  of  the  remainder 
of  the  process.  The  neglect  of  this  apparently  trifling  point  is  often 
the  cause  of  entire  failure,  or  at  least  of  great  inconvenience,  and  not 
^infrequently  leads  to  the  production  of  imperfect  and  faulty  prepa- 
rations ;  as,  owing  to  the  uncertainty  of  the  composition  of  the 
liquid  after  evaporation  has  once  been  permitted,  its  loss  cannot  be  sup- 
plied with  any  degree  of  accuracy,  especially  when  it  is  a  liquid  of  a 
compound  nature ;  such,  for  instance,  as  alcohol. 
Formulas  are  in  this  way  sometines  blamed  for  imperfections  when 
it  is  the  carelessness  or  inattention  of  the  operator  that  is  at  fault. 
Much  care  is  also  necessary  in  the  concentration  of  the  last  portion 
of  the  percolate  in  making  fluid  extracts  ;  where  the  liquid  to  be 
evaported  is  a  simple,  as  water,  ether,  chloroform,  &c,  the  same  care 
is  not  requisite  to  guard  against  excessive  concentration,  as  the  loss, 
in  such  cases,  may  be  supplied  by  the  addition  of  fresh  portions  of 
the  respective  liquids  ;  nor  is  it  so  important  even  when  alcohol  is  the 
liquid  under  treatment,  if,  in  the  operation,  all  of  the  alcohol  is  supposed 
to  be  expelled,  because  then  water  may  be  used  to  make  up  the 
loss,  but  if  the  spirit  is  to  be  only  partially  driven  off,  then  care  is 
absolutely  necessary,  for  reasons  just  stated. 
