ON  CHEMISTRY  APPLIED  TO  THE  ARTS.  263 
wrong  in  me  to  leave  you  under  the  impression  that  animal  black 
can  only  remove  colors  from  solutions.  Purified  animal  black — 
that  is  to  say,  animal  black  deprived  of  its  mineral  matters  by 
the  action  of  muriatic  acid  and  subsequent  washing — has  the 
power  of  removing  certain  bitters  from  their  solutions.  Thus 
Dr.  Hofmann  and  Professor  Redwood  applied  this  property  with 
great  skill  some  years  ago  to  the  detection  of  strychnia  in  beer. 
Again,  Thomas  Graham,  Esq.,  Master  of  the  Mint,  published  a 
most  interesting  series  of  researches,  in  which  he  established  the 
fact  that  purified  animal  black  had  the  power  to  remove  a  great 
number  of  saline  matters  from  their  solutions,  such  as  the  salts 
of  lime,  lead,  copper,  &c. 
Revivification  of  Bone  Black. — After  a  certain  quantity  of 
syrup  sugar  has  percolated  through  the  cylinders  containing 
bone-black,  the  interstices  become  so  clogged  with  impurities 
that  it  loses  its  power  of  decolorating  the  syrup.  Sugar  re- 
finers are  therefore  in  the  habit  of  restoring  the  power  of  their 
bone-black,  generally  speaking,  by  submitting  it  to  a  process  of 
calcination,  which  volatilises  or  destroys  the  organic  matter 
fixed  by  the  char.  It  has  been  proved  by  experience  that  char 
may  undergo  this  operation  about  twenty  times  before  its  pores 
become  so  clogged  with  dirt  as  to  render  it  useless.  [Here  the 
lecturer  described,  with  the  aid  of  drawings,  several  of  the  vari- 
ous apparatus  used  in  sugar  refineries  for  the  above  process,  al- 
luding particularly  to  that  of  Messrs.  Pontifex  and  Wood,  by 
which  a  ton  of  char  is  revivified  every  twenty-four  hours.]  A 
new  process,  however,  has  been  devised  by  Messrs.  Leplay  et 
Cuisinier,  which  as  a  whole  deserves  the  attention  of  refiners, 
though  I  am  aware  that  several  of  the  details  of  their  process 
have  been  used  for  some  time.  The  char  which  has  served  its 
purpose  in  the  cylinders,  instead  of  being  removed,  is  treated  at 
once  by  the  following  processes : — It  is  first  thoroughly  washed, 
treated  by  steam  to  remove  all  viscous  substances,  then  a  weak 
solution  of  alkali  is  allowed  to  percolate  through  the  char,  which 
removes  saline  matters  and  a  certain  amount  of  coloring  matter, 
when  it  is  further  acted  upon  by  weak  hydrochloric  acid,  which, 
in  removing  a  certain  amount  of  the  lime  salts,  liberates  the 
coloring  matter ;  the  char  is  again  washed  with  weak  alkali  to 
