ON  FLUID  EXTRACTS. 
523 
separately  evaporated,  and  mixed.  The  amount  of  the  liquids 
after  concentration  should  be  so  arranged  that,  when  mixed,  the 
percentage  of  the  menstruum  in  the  Extract  shall  be  just  high 
enough  to  hold  in  solution  the  substances  extracted  by  the  alco- 
hol. If  so  calculated,  the  larger  part  of  the  aqueous  extract 
will  dissolve,  and  the  sediment  which  falls  will  possess  little 
value. 
There  is  little  needs  to  be  said  upon  the  subject  of  evapora- 
tion. On  the  large  scale,  much  is  gained  by  using  the  vacuum 
pan,  while  for  smaller  operations  the  water  bath  must  be  re- 
sorted to.  This  subject  of  evaporation  is  ably  treated  in  the 
United  States  Dispensatory,  and  I  know  of  little  to  add.  The 
degree  of  concentration  for  Non-officinal  Extracts  should  be 
governed  by  the  following  rule,  which  appears  most  applicable, 
viz.,  That  each  fluid  ounce  of  Extract  should  represent  one 
ounce  of  raw  material. 
The  great  difficulty  in  perfecting  this  new  form  of  Extracts 
has  been  to  conquer  the  tendency  which  vegetable  substances 
possess  to  enter  upon  a  state  of  acetous  fermentation.  To  coun- 
teract this  tendency,  the  officinal  directions  are,  except  for  oleo- 
resinous  and  purely  alcoholic  Extracts,  to  add  sugar,  thus  form- 
ing syrups.  Experience  has  shown  that  such  preparations  are 
not  permanent,  and  the  rule  will  only  answer  for  those  that  are 
made  in  small  quanties,  to  be  kept  for  a  short  time.  Another 
and  serious  objection  is  that  in  the  precipitates  the  lumps  which 
form  during  the  concentration  of  Hydro-alcoholic  Extracts  are 
with  difficulty  subdivided  so  as  to  give  the  Fluid  Extract  uni- 
formity ;  and,  again,  however  well  the  extractive  matters  are 
suspended,  they  are  apt  in  time  to  settle,  and  form  a  concretion. 
This  class  of  preparations  should  be  so  prepared  that  they  will 
be  permanent  preparations,  admitting  of  transportation  to  any 
climate,  of  equal  value  at  all  times  and  under  all  circumstances. 
Alcohol  approaches  most  nearly  the  character  of  a  permanent 
preservative  of  any  substance  available  for  this  purpose,  and 
possesses  this  advantage, — that  when  added  to  the  evaporated 
liquid,  the  precipitates  re-dissolve,  and  form  a  beautiful  solution. 
The  only  objection  to  its  use  arises  from  its  stimulating  effects  
an  objection,  however,  that  is  but  little  urged,  and  which,  except 
in  rare  cases,  has  little  force.  The  proportion  of  alcohol  re- 
quisite is  seldom  over  20  per  cent.,  and  the  small  amount  of  the 
