CLARIFICATION  OF  SACCHARINE  LIQUIDS.  553 
of  the  charcoal  can  be  divided  into  three  periods,  which  we  will 
examine  successively. 
The  first  series  of  absorbing  properties  is  almost  entirely  ex- 
hausted after  a  few  hours'  filtering, — say,  under  ordinary  cir- 
cumstances, about  four  hours.  These  are  the  properties  which 
affect  viscous,  nitrogenised,  ammoniacal,  sapid,  and  odorous 
matters,  which  injure  the  fluidity  of  syrups,  their  crystallization, 
the  hardness  and  consistence  of  the  grain,  the  quantity  and 
quality  of  the  sugar,  and  which  impart  to  rough  sugars  the  odor 
and  flavor  peculiar  to  the  produce  of  the  beet-root.  We  com- 
pletely re-establish  the  primitive  absorbing  properties  by  passing 
a  current  of  steam  through  the  granulated  animal  charcoal  con- 
tained in  the  filter.  The  absorbing  properties  of  animal  char- 
coal can  thus  be  regenerated  indefinitely. 
A  much  longer  time  is  required  to  exhaust  the  second  series 
of  absorbing  properties.  They  last  six  or  eight  times  as  long 
as  those  of  the  first  series.  The  period  of  exhaustion  varies 
with  the  alkalinity  of  the  defecated  juices  and  syrups.  Free  al- 
kalies, lime,  potash,  soda,  salts  of  lime,  and  other  saline  matters 
are  absorbed  by  the  series  in  question.  These  matters  especi- 
ally contribute  to  color  the  juices  and  syrups  during  evaporation 
by  destroying  the  sugar,  and  when  present  in  large  proportion 
prevent  crystallization.  We  revive  these  absorbing  properties 
by  pouring  a  weak  solution  of  hydrochloric  acid  over  the  char- 
coal contained  in  the  filter  and  by  sufficiently  prolonged  wash- 
ings in  water. 
The  third  series  comprise  the  absorptive  properties  of  charcoal 
for  coloring  matters.  They  last  thirty  or  forty  times  as  long 
as  the  first  series.  Moreover,  the  presence  of  coloring  matters 
in  these  syrups  is  of  no  great  importance  when  they  are  trans- 
parent and  brilliant  and  hold  no  matter  in  suspension.  White 
sugars  can  be  obtained  from  colored  syrups,  and  when  from 
the  tint  of  the  products,  it  is  deemed  necessary  to  revivify  the 
power  of  absorbing  coloring  matters,  we  make  use  for  this  pur- 
pose of  a  weak  solution  of  boiling  caustic  alkalies. 
We  use  these  various  means  of  revivification  either  in  the 
filter  itself  or  in  a  special  apparatus  similar  to  the  filter. 
The  various  methods  of  revivification  just  described,  restore 
the  absorbing  properties  of  the  animal  charcoal  to  their  primi- 
