430     THE  ANIMAL  CHARCOAL  USED  IN  SUGAR  REFINING. 
to  follow.  When  very  hard  water  is  used  the  carbonate  of  lime 
either  decreases  very  slightly  or  it  increases,  and  sometimes 
even  to  an  alarming  extent,  as  in  the  continental  beet  refineries, 
where  the  evil  is  a  very  serious  one. 
Dr.  Wallace  referred  to  the  various  methods — especially  those 
of  Beanes  and  Gordon — -for  getting  rid  of  any  excess  of  carbo- 
nate of  lime  in  the  charcoal ;  and  then  spoke  of  the  inconveni- 
ence attending  the  use  of  animal  charcoal  in  sugar-refining, 
owing  to  its  oxidizing  influence  upon  the  organic  matters  ex- 
tracted by  the  char  from  the  sugar,  and  to  the  alteration  of  the 
nitrogenous  compounds  by  means  of  which  fermentation  is 
induced,  and  ultimately  organic  acids  are  formed  at  the  expense 
of  the  sugar.  These  acids  make  the  washings  sour  and  putrid, 
«  and  a  necessary  and  evil  result  of  that  is  that  they  decompose 
sulphide  of  calcium  or  sulphide  of  iron  in  the  charcoal,  and  dis- 
solve carbonate  and  sulphate  of  lime  and  oxide  of  iron ;  then, 
as  the  washings  are  either  thrown  back  amongst  the  other  pro- 
ducts of  the  refinery,  or  mixed  with  a  fresh  lot  of  raw  sugar, 
they  occasionally  cause  an  immense  amount  of  mischief.  The 
author  said  that,  owing  to  its  importance,  this  department  of 
sugar  refining  had  occupied  a  good  deal  of  his  attention,  and  he 
claimed  to  have  made  known  to  refiners  the  means  of  entirely 
preventing  such  injurious  results  as  those  referred  to.  His 
method  is  a  follows : — While  the  liquor  is  on,  the  char  cisterns 
are  kept  at  a  temperature  of  at  least  150°  Fahr.,  so  long  as  the 
liquor  is  strong,  to  prevent  fermentation.  Then  the  water  used 
for  washing  down  the  sugar  is  to  run  on  quite  boiling,  and  this 
is  done  with  all  the  washings  which  are  to  be  preserved.  When 
these  directions  are  attended  to,  there  is  no  difficulty  with  sour 
washings,  or  with  the  presence  of  iron  in  the  low-class  sugars. 
The  char  should  ultimately  be  washed  with  boiling  water  for  10 
or  12  hours,  or  even  boiled  with  it. 
The  author  concluded  with  a  detailed  account  of  the  modes  of 
re-burning  charcoal,  and  of  the  good  and  bad  qualities  of  the 
different  kinds  of  re-burners  now  in  use,  and  suggested  the 
directions  in  which  improvements  might  be  made.—  Lond.  Chem. 
Neivis,  May  22,  1868. 
