FACTS  CONNECTED  WITH  SUGAR  REFINING. 
185 
of  sulphur  in  the  syrup  might  not  be  the  cause  of  the  phenomena 
observed.  The  experiments  described  in  my  note  have  led  me 
to  results  which  may  be  given  in  the  following  propositions. 
The  syrups  clarified  with  infected  blood,  the  albumen  of  which 
has  begun  to  decompose,  communicate  to  the  charcoal  properties 
which  repeated  revivifications  render  extremely  evident  and 
annoying. 
Charcoal  in  which  have  accumulated  compounds  with  a  base 
of  sulphur,  injure  the  limpidity  and  color  of  the  saccharine  solu- 
tion and  tend  to  augment  the  quantity  of  molasses. 
The  employment  of  hydrochloric  acid  and  the  estimation  of 
sulphur  in  the  state  of  sulphuret  of  copper,  enabled  us  to  com- 
pare and  judge  a  priori  okf  the  charcoals,  which  would  give  dif- 
ferent results  in  manufacture,  notwithstanding  their  apparent 
identity. 
I  come  now  to  the  examination  of  those  means  by  which  these 
serious  inconveniences  may  be  avoided.  Their  principles  are 
derived  from  the  very  nature  of  the  facts  which  I  have  just  de- 
scribed. 
Washing  the  charcoal  with  hydrochloric  acid  at  4°  Baume',  in 
an  apparatus  in  which  the  rotation  of  the  solid  substance  would 
be  combined  with  the  flowing  of  the  liquid,  would  decompose  the 
sulphurets  by  producing  a  disengagement  of  hydrosulphuric  acid. 
On  a  small  scale  this  operation  succeeds  perfectly,  the  liquids 
charged  with  acid  phosphate  of  lime,  producing  by  the  ulterior 
influence  of  milk  of  lime,  a  gelatinous  precipitate  of  basic  phos- 
phate of  lime,  of  great  value  in  agriculture. 
Washing  with  pure,  tepid  water,  or  water  rendered  slightly 
alkaline  with  carbonate  of  soda,  will  prevent  the  possibility  of 
any  acid  remaining  in  the  pores  of  the  charcoal.  Besides  this 
method,  which  was  very  successful  on  a  small  scale,  there  is 
another  which  I  would  propose  :  namely,  to  eliminate  as  far  as 
possible,  in  summer,  all  the  revivified  charcoal,  that  is  to  say,  to 
put  as  much  new  charcoal  into  the  filters  as  would  be  possible 
with  a  due  regard  to  economy.  This  new  charcoal  should  not 
be  mixed  with  what  is  in  the  filter,  but  placed  in  the  lower  part 
of  it,  so  that  the  syrup,  partly  freed  from  the  coloring  matter  by 
the  charcoal  at  the  top,  but  still  impregnated  with  the  decom- 
