ON  GLUCOSE. 
413 
it  is  intended  to  make  sugar  the  whole  of  the  starch  is  converted, 
but  if  syrup  is  sought  then  some  part  of  dextrine  is  left  un- 
altered. The  acid  liquor  is  neutralized  with  chalk  as  before, 
and  evaporated  in  vacuum  pans,  and  after  the  separation  of  the 
gypsum  is  run  into  barrels  and  allowed  to  crystallize.  For 
syrup  a  certain  percentage  of  dextrine  is  left  in  the  liquid  un- 
converted, which  helps  to  keep  it  from  crystallizing,  and  in  the 
manufacture  of  syrup  special  care  must  be  observed  to  neutralize 
all  of  the  acids.  The  sugar  is  sometimes  cast  into  blocks  six 
inches  square  and  dried  on  plaster  plates,  in  a  current  of  dry 
air,  as  hot  air  would  be  apt  to  discolor  it.  It  has  been  found 
that  glucose  can  be  made  from  cellulose  as  well  as  from  starch, 
but  the  process  is  too  expensive  for  practice ;  it  is,  however,  in- 
teresting from  a  scientific  point  of  view,  and  ought  to  be  men- 
tioned in  this  connection. 
Two  parts  of  clean  linen  shreds  are  gradually  added  to  three 
parts  of  sulphuric  acid,  and  they  are  allowed  to  stand  twenty- 
four  hours  ;  the  whole  is  then  largely  diluted,  and  the  sulphuric 
acid  neutralized  by  carbonate  of  lime  or  carbonate  of  baryta. 
In  a  similar  manner  any  other  kind  of  cellular  tissue,  as  cotton, 
wood  shavings,  paper,  etc.,  can  be  converted  into  grape  sugar. 
It  is  a  singular  fact  that,  although  we  can  prepare  grape  sugar 
from  cane  by  the  action  of  acids,  no  way  is  at  present  known 
by  which  glucose  can  be  re-converted  into  sucrose.  It  would  be 
a  discovery  of  great  importance  if  we  could  make  cane  sugar 
from  glucose,  as  in  that  event  common  sugar  could  be  prepared 
from  a  great  variety  of  refuse  matters,  and  would  be  largely  re- 
duced in  price. 
There  was  a  time  when  much  grape  sugar  was  manufactured 
in  England  clandestinely,  for  the  purpose  of  adulterating  Mus- 
covado sugar,  but  this  illegitimate  business  was  destroyed  as  soon 
as  the  tariff  on  sugar  was  reduced.  The  price  of  cane  sugar 
must  be  very  high  before  manufacturers  can  afford  to  make  grape 
sugar  for  its  adulteration. 
The  starch  of  potatoes  can  be  converted  into  glucose  by  di- 
gesting for  a  few  hours  with  parings  of  the  potato.  This  opera- 
tion is  largely  practised  by  German  farmers  in  the  preparation 
of  food  for  fattening  hogs.  The  starch  is  rendered  more  di- 
gestible in  this  way,  and  from  the  glucose  some  of  the  larger 
