532  PROCESS  FOR  "preparing  JAMES'  POWDER. 
experiments  convinced  me  that  the  heating  in  the  ladle  is  the 
most  important  part  of  the  whole  process  ;  and  at  length  it  be- 
came evident  that  when  the  heat,  accompanied  by  continued 
stirring  or  raking,  was  maintained  until  the  powder  changed 
from  dark  brown  to  a  light  yellowish-grey,  the  final  heating  in 
a  skittle-pot  brightened  it,  or  the  greater  part  of  it,  to  a  perfect 
white.  The  light  yellowish-grey  color  hero  mentioned  will  be 
best  understood  by  comparing  it  to  the  dust  of  a  Bath  brick, 
often  used  for  cleaning  dinner  knives,  but  a  little  paler. 
But  to  heat  the  powder  while  in  the  ladle  fully  to  this  color, 
but  not  beyond  it,  was  the  difficulty. 
During  these  experiments  I  perceive<I  that  when  the  quanti- 
ties of  the  two  ingredients  were  as  large  as  ten  ounces  of  each, 
the  resulting  powder  when  taken  from  the  skittle-pot  never 
proved  white,  but  generally  dark  grey,  interspersed  with  a  deep 
yellow-colored  portion.  This  fact  pointed  to  the  conclusion  that 
the  ladle  was  too  small  for  that  quantity  of  materials,  that  due 
raking  during  the  heating  was  impeded,  and  \Jiiit  the  desulphura- 
tion  was  accordingly  imperfect.  A  hemispherical  ladle  capable 
of  holding  a  gallon  being  procured,  a  charge  of  ten  ounces  of 
each  was  placed  on  the  fire  and  continually  raked  for  several 
hours,  at  first  without  any  intermission,  and  at  length  with  short 
intervals  of  rest,  until  the  proper  color  was  attained.  This 
matter,  being  finely  powdered,  was  introduced  into  a  proportion- 
ately large  skittle  pot  and  exposed  to  a  well-built  coal  fire  in  a 
common  grate,  and  kept  red-hot  for  three  hours.  When  cold, 
the  top  portion  proved  to  be  a  thin  cake  of  dark-colored  matter ; 
under  that  was  a  small  quantity  of  yellow  portion  ;  and  the  re- 
mainder was  very  nearly  snow-white. 
On  trying  so  large  a  charge  as  sixteen  ounces  of  each  ingre- 
dient in  the  large  ladle  it  proved  to  be  unmanageable ;  the  car- 
bon at  an  early  period  ignited  ;  the  mass  softened,  collected  into 
dark-colored  lumps,  which  could  not  be  raked  notwithstanding 
much  effort.  Finding  it  impracticable,  I  took  out  the  charge 
when  cold,  and  being  powdered,  it  was  returned  into  the  ladle 
in  four  different  portions,  each  of  wdiich  was  separately  raked 
while  heating,  until  the  proper  color  appeared  to  be  attained. 
The  whole  of  the  powder  being  charged  into  a  very  large  skittle- 
