ON  THE  PREPARATION  OF  FLUID  EXTRACTS.  153 
the  Pharmacopoeia,  a  powder  moderately  fine,  or  one  that  would 
pass  through  a  sieve  No.  50,  would  be  preferable  to  the  one 
adopted  bj  Mr.  Campbell,  which  is  moderately  coarse,  or  one 
that  would  pass  through  a  sieve  No.  40.  Almost  any  drug  can 
be  reduced  to  this  degree  of  fineness,  without  involving  much 
more  labor  or  time  than  is  required  to  reduce  it  to  a  moderately 
coarse  powder.  Of  the  23  fluid  extracts  now  ofiicinal,  in  which 
fineness  of  powder  is  indicated,  eleven  are  directed  to  be  made 
from  moderately  fine  powder  (No.  50,)  and  twelve  from  fine 
powder  (No.  60) ;  these  two  grades  being  the  only  ones  indi- 
cated. 
When  powders  finer  than  No.  50  are  directed  they  will 
rarely  be  prepared  by  the  apothecary,  but  will  be  purchased 
from  the  wholesale  druggist,  or  the  drug  grinder,  and  will  con- 
sequently be  much  more  liable  to  be  inert,  impure  or  adulterated 
than  when  powdered  under  the  supervision  of  one  who  wishes  to 
prepare  his  own  extracts. 
Two  of  the  fluid  extracts  of  the  Pharmacopoeia,  viz.,  those  of 
hemlock  and  ergot,  have  a  small  quantity  of  acetic  acid  added 
to  the  menstruum  ;  and  this  is  a  very  useful  addition  to  those 
preparations  when  made  according  to  the  formula  of  the  present 
Pharmacopoeia.  The  main  object  of  this  addition  is  to  give 
stability  to  the  alkaloids  during  the  process  of  concentrating 
these  extracts  by  heat ;  it  is  also  incidentally  useful  in  promoting 
the  solubility  of  the  alkaloids,  and  in  preserving  the  preparations 
when  finished.  These  objects  are  all  accomplished  by  the  pro- 
cess of  Mr.  Campbell,  without  the  addition  of  the  acid.  No  heat 
being  used  in  the  process,  all  danger  of  destruction  from  this 
cause  is  avoided.  The  menstruum  being  sufficient  to  completely 
exhaust  the  drug,  no  addition  is  required,  while  the  glycerin  is 
perhaps  a  better  preservative  of  the  finished  preparation  than 
acetic  acid. 
As  Mr.  Campbell  has  well  said,  a  fluid  extract  should  repre- 
sent the  drug  from  which  it  is  prepared,  giving  the  constituents, 
as  nearly  as  possible,  as  they  exist  in  the  crude  drug ;  and 
although  acidulated  preparations  of  cinchona,  opium,  conium, 
&c.,  may  be  desirable,  it  is  at  least  questionable  whether  acetic 
or  any  other  acid,  whereby  the  natural  composition  is  changed, 
