Amseptu"  i?77arm'}  Preparation  of  Extracts  without  Heat.  439 
until  the  solution  is  of  the  same  density  as  the  natural  juice.  The 
method  is  also  advantageous  in  the  preparation  of  syrups  in  serving  to 
properly  concentrate  the  liquors  from  which  the  syrups  are  made. 
For  the  extracts  prepared  from  juices  by  the  method  indicated,  the 
author  proposes  the  designation  of  opopycnols  (opopicnolees),  derived 
from  the  two  Greek  words  07roc,  the  juice,  and  nuxvoco,  to  condense. 
In  obtaining  artificial  extractive  solutions,  the  process  of  infusion 
should  be  used,  unless  the  active  principles  are  sparingly  soluble  in 
water,  in  which  case  digestion  or  even  decoction  may  be  resorted  to, 
but  in  whichever  way  obtained,  the  solutions  are  treated  alike  for  pre- 
paring the  extracts.  Extract  of  rhatany,  prepared  by  the  process  of 
congelation,  dissolves  completely  in  water,  with  a  red  color,  and  has  a 
much  more  astringent  taste,  compared  with  the  extract  which  was  pre- 
pared with  the  utmost  precaution  by  evaporation  in  a  water  bath. 
Similar  comparisons  were  made  with  the  extracts  of  catechu,  aloes  and 
others,  and  in  all  cases  a  very  notable  difference  was  observed,  which 
is  explained  by  the  final  evaporation  in  the  proposed  process  being  con- 
ducted by  the  heat  of  the  sun  or  of  the  drying  closet,  which  is  insuffi- 
cient to  effect  a  change  or  to  volatilize  the  volatile  principles  in  anv 
appreciable  degree. 
The  apparatus  employed  by  me  is  the  so-called  sorbetiere  ; 1  for  larger 
quantities  the  apparatus  of  Gougaud  is  preferable.  The  frigorific 
mixture  is  composed  of  ice  and  sodium  chloride,  or  preferably  of  crys- 
tallized calcium  chloride.  After  a  large  portion  of  the  solution  has 
congealed,  the  mass  is  enclosed  in  a  cloth  and  subjected  to  pressure, 
the  presscake  of  ice  is  broken  and  again  pressed,  to  separate  the  mother 
liquor  as  completely  as  possible,  and  the  congelation  is  repeated  two  or 
three  times,  with  the  precaution  that  it  be  not  carried  far  enough  to 
cause  the  precipitation  of  the  sparingly  soluble  principles.  The 
mother  liquor  is  then  put  into  shallow  dishes  and  exposed  to  the 
heat  of  the  sun  or  of  a  drying  room,  the  temperature  of  which  does 
not  exceed  3o°C,  (86°F.)  until  the  extract  has  attained  the  desired 
consistence. 
In  conclusion,  it  may  be  stated  that  the  concentration  of  aqueous 
solutions  by  congelation  appears  to  be  preferable 
1.  For  the  preparation  of  aqueous  extracts  in  general. 
SimiUr  to  the  apparatus  used  here  for  making  ice  cream. — Editor. 
