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14  ON  SOME  PHABMACEUTICAL  PREPARATIONS. 
for  maceration,  this  is  set  aside,  the  opium  exhausted  by  water, 
and  the  last  obtained  liquid  evaporated  first  to  a  syrupy  consist- 
ence before  the  first  part  is  added ;  thus  a  complete  exhaustion 
of  the  opium  is  made  sure  of,  and  the  contact  of  the  liquid  with 
the  atmosphere  avoided  as  much  as  possible. 
Tincture  of  Jlbps.— -Hops  are  too  bulky  to  allow  of  their  being 
used  for  the  process  of  displacement  without  having  been  previously 
reduced  to  a  moderately  fine  powder;  this,  however,  cannot  easily 
be  obtained ;  even  well  dried  hops  have  a  tendency  to  cake  when 
pounded  in  a  mortar,  and  to  clog  the  teeth  of  Swift's  drug-mill ; 
but  if,  as  soon  as  the  clogging  is  perceived,  a  little  fine  dry  sand 
is  run  through  the  mill,  the  teeth  are  cleaned  sufficiently,  and 
thus  by  alternately  passing  hops  and  fine  sand  through,  a  con- 
siderable quantity  may  be  ground  with  little  trouble.  After 
grinding  12  oz.  hops,  I  took  the  mill  apart  to  clean  it,  when 
scarcely  one  drachm  was  found  sticking  between  the  teeth. 
Rather  less  than  3  oz.  of  sand  were  found  sufficient  to  aid  in 
grinding  this  quantity  of  hops  to  a  pretty  fine  powder.  The 
powdered  hops  are  put  into  a  percolator,  and  after  having  been 
thoroughly  moistened  with  diluted  alcohol,  are  packed  tightly  ; 
then  12  oz.  do  not  quite  fill  the  space  of  three  pints.  In  this 
state,  and  mixed  with  such  a  small  quantity  of  sand,  hops  are 
admirably  adapted  for  the  process  of  displacement,  and  easily 
exhausted  by  diluted  alcohol,  the  last  portion  of  which  may  be 
displaced  by  water,  which  being  retained  by  the  hops  in  con- 
siderable quantity  causes  them  to  swell. 
Syrup  of  Citric  Acid. — The  readiness  of  this  syrup  to  acquire 
a  more  or  less  disagreeable  odor  or  taste,  may  be  partially  due 
to  the  changeableness  of  citric  acid  in  an  aqueous  solution,  though 
this  tendency  is  counteracted  by  the  sugar  ;  chiefly/however,  it 
must  be  referred  to  the  oil  of  lemon  used  for  flavoring,  which,  by 
its  exposure  to  the  air,  may  have  lost  the  delicate  odor  of  the 
lemon  peel  by  oxidation,  thus  assuming  a  more  terebinthinate 
smell  and  taste.  This  disposition  of  the  artificial  lemon  syrup 
to  deteriorate,  may  in  a  very  great  measure  be  obviated  by  em- 
ploying an  essence  for  flavoring  prepared  of  6  oz.  of  the  yellow 
rind  of  fresh  lemons  to  one  pint  of  95  per  cent,  deodorized  alco- 
hol. The  lemon  rind  in  its  fresh  state  is  covered  with  some 
alcohol  for  several  hours,  when  it  becomes  so  friable  as  to  be 
