120  ON  THE  PRESERVATION  OF  FLUID  EXTRACTS. 
generally  unsightly  and  in  some  cases  even  repulsive.  When- 
ever it  is  in  our  power,  we  owe  it  to  the  suffering  to  remedy  this 
defect  by  making  the  medicine  as  transparent  as  possible.  Al- 
coholic tinctures  when  freshly  prepared,  are  unexceptionable  as 
far  as  their  appearance  is  concerned,  but  above  I  have  shown 
that  they  are  subject  to  changes  and  form  precipitates.  This  is 
admitted  by  M.  Thayer,  but  he  thinks  this  tendency  is  less  in 
fluid  extracts  than  in  tinctures,  doubtless  so  on  account  of  their 
specific  gravity  being  higher.  I  have  had  little  experience  with 
alcoholic  fluid  extracts,  a  few  instances  excepted  ;  but  if  I  am  to 
judge  from  them  and  the  conclusions  of  the  above  stated  well 
established  facts,  it  appears  to  me  that  they  all  must  soon  pre- 
cipitate, and  though  the  precipitate  be  light  and  more  pulveru- 
lent, and  may  by  agitation  be  easily  mixed  with  the  extract, 
still  this  does  not  improve  their  appearance,  but  certainly  ren- 
ders them  more  or  less  unsightly. 
In  making  fluid  extracts,  the  obtained  tincture  or  infusion  du- 
ring the  process  of  evaporation  is  heated  for  such  a  length  of 
time,  that  by  contact  with  air  a  partial  change  is  unavoidable ; 
the  darker  color  of  the  liquid  and  sometimes  the  portions  of  in- 
soluble matter  floating  therein  are  evidences  thereof.  The  ad- 
dition of  sugarin  such  cases,  may,  by  its  own  solvent  powers,  dis- 
solve some,  or  keep  that  extractive  matter  suspended  for  a  time  ; 
but  if  suspended  only,  it  is  sure  to  separate  and  thus  detract 
from  the  nicety  of  the  preparation.  This  result  may  be  avoided  by 
straining  the  fluid  extract  before  the  addition  of  the  sugar  through 
close  flannel,  or  better  still  by  filtering  it  quickly  through  good 
filtering  paper,  while  yet  hot,  and  washing  the  filter  subsequently 
with  hot  water  to  make  up  for  the  loss  suffered  by  evaporation. 
The  separation  of  apotheme  from  the  fluid  extracts  ought  to  be 
a  necessity,  as  it  contributes  nothing  at  all  to  the  medicinal  pro- 
perties of  the  preparation,  and  as  it  is  a  substance  in  the  process 
of  alteration,  it  most  likely  interferes  with  the  stability  of  the 
fluid  extract.  Alcohol  is  a  better  solvent  for  this  substance, 
which  consequently  enters  greally  into  the  extracts  preserved 
by  alcohol,  without  adding  to  their  stability. 
Besides  apotheme,  during  evaporation  other  bodies  may  be 
separated,  particularly  chlorophyll  and  resin ;  the  first  of  the  two 
W7e  had  better  get  rid  of  in  all  our  preparations,  with  the  latter, 
