462 
PURIFICATION  OF  VEGETABLE  JUICES. 
ide  of  iron,  on  account  of  its  property  (well  known  to  chemists^ 
of  absorbing  alkaline  and  earthy  salts,  removes  the  small  quan- 
tity of  the  sulphate  of  lime  which  was  left  in  the  solution.  Thus, 
the  juice  which,  after  defecation  by  sulphate  of  lime,  reduced 
nitrate  of  silver,  protoxide  of  mercury,  &c.,  will  produce  no 
alteration  in  these,  after  its  own  contact  with  oxide  of  iron. 
The  juice,  when  it  proceeds  from  a  vegetable  taken  in  a  nor- 
mal condition,  is  perfectly  neutral  to  test  paper,  after  this  pu- 
rification, and  may  be  preserved  in  contact  with  the  air  for  sev- 
eral days,  without  its  undergoing  the  slightest  alteration  or  col- 
oration, which  proves  that  all  the  substances  capable  of  acting 
the  part  of  a  ferment  have  been  removed.  It  can  be  boiled, 
without  coloring  under  the  action  of  the  heat.  The  syrup  car- 
ried to  the  point  of  candying  possesses  only  the  slight  yellow 
color  peculiar  to  all  the  purest  syrups.  Its  taste  is  pleasant, 
devoid  of  that  saline  and  disagreeable  taste  which  is  found  in 
the  syrup  of  the  beet,  and  it  preserves  a  remarkable  fluidity 
and  limpidity.    It  crystallizes  readily,  the  crystals  being  white. 
As  the  last  proof  of  a  good  purification  of  saccharine  juice  in 
this  way,  if  we  add  to  some  of  the  boiled  syrup  a  suflScient 
quantity  of  water  so  that  the  areometer  could  stand  at  from  25^ 
to  30°,  and  then  mix  it  with  a  large  excess  of  alcohol  of  90, 
there  will  be  produced  neither  turbidness  nor  deposit  after  days 
standing, — showing  that  not  a  trace  of  air  is  present. 
Henceforward  the  manufacture  of  sugar  is  reduced  to  the  fol- 
lowing manipulations  :  to  heat  the  saccharine  juice  in  a  boiler 
along  with  a  few  thousandths  of  sulphate  of  lime  (crude  plaster 
is  the  best),  all  the  coagulable  substances  will  collect  in  a  com- 
pact scum  :  the  clean  juice  is  then  agitated  with  the  sesquioxide 
of  iron.  After  the  separation  of  the  sesquioxide,  it  only  re- 
mains to  evaporate  the  water,  that  is  to  say,  to  boil  it. 
The  form  of  hydrated  sesquioxide  of  iron  which  seemed  most 
fitted  was  that  of  a  consistent  paste.  A  litre  weighs  about 
1.145  grm.,  containing  from  70  to  80  parts  to  100  of  water. 
The  quantity  to  be  employed  varies  with  the  nature  of  the  veg- 
etable, its  own  condition  and  state  of  preservation.  It  should 
not  exceed,  as  the  extreme  limit,  8  to  10  parts  to  100  of  juice, 
— which  amounts  to  about  2  parts  to  100  parts  of  solid  sub- 
stance, the  remainder  being  water. 
