344  On  Monobromated  Camphor.  {k\lTS™' 
the  glass  stopper ;  now  a  thermometer  is  inserted,  and  the  retort 
slowly  heated  ;  a  rapid,  but  regular  evolution  of  hydrobromic  acid 
gas  takes  place  as  the  temperature  increases ;  the  golden  yellow  nee- 
dles, mostly  condensed  in  the  neck,  fuse  and  run  back,  and  when  the 
temperature  has  gradually  reached  about  120°  C,  (248°  F.,)  the 
liquid  boils  somewhat  and  the  evolution  of  gas  slackens.  From  and 
above  90°  C,  (194°  F.,)  the  deep  red  color  of  the  liquid  becomes 
much  lighter,  and  if  the  heat  is  raised  to  about  132°  C,  (270°  F.,) 
the  color  will  not  deepen.  At  a  somewhat  higher  temperature,  par- 
ticularly when  nearing  150°  C,  (302°  F.,)  the  liquid  soon  becomes 
darker  and  finally  black. 
When  the  temperature  has  reached  132°  C. — which  should  require 
not  less  than  three  hours — the  fire  is  withdrawn  and  the  retort  allowed 
to  cool  to  about  50  or  55°  C,  (120  to  130°  F.);  the  contents  are  dis- 
solved in  12  oz.  of  petroleum  benzine,  and  the  solution  is  poured  into 
a  beaker  glass  containing  some  warm  water  and  pieces  of  marble  to 
neutralize  the  free  acid  still  present.  While  cooling,  the  benzine  so- 
lution is  occasionally  stirred  to  disturb  the  crystallization.  On  the  fol- 
lowing morning,  the  liquid  matter  is  poured  off,  the  benzine  mother- 
liquor  separated  from  the  aqueous  solution  of  bromide  of  calcium,  and 
the  crystals  drained  upon  a  funnel,  the  neck  of  which  is  loosely  stopped 
with  some  cotton.  Petroleum  naphtha  or  gasoline  is  poured  upon  them 
until  they  change  but  little  in  color  when  exposed  to  the  direct  sun- 
light. When  dry  the  crystals  will  weigh  about  twelve  ounces;  for 
complete  purification  they  require  to  be  recrystallized  from  alcohol  or 
petroleum  benzine. 
More  crystals  may  be  obtained  by  evaporating  the  benzine  mother- 
liquor  to  one-half  and  washing  them  first  with  the  naphtha  solution  and 
then  with  some  fresh  naphtha.  The  mother-liquor,  not  yielding  suf- 
ficiently pure  crystals,  is  evaporated,  heated  in  a  retort  to  260°  C, 
(500°  F.,)  when  it  boils  again,  evolving  hydrobromic  acid.  When  the 
evolution  of  the  latter  slackens,  the  black  mass,  after  cooling  suffi- 
ciently, is  taken  up  with  benzine,  the  solution  treated,  as  before,  with 
warm  water  and  an  alkali  (marble)  and  set  aside  to  crystallize ;  the 
black  crystals  are  redissolved  in  alcohol  or  benzine,  the  solution  fil- 
tered and  crystallized.  The  crystals  require  to  be  washed  with  petro- 
leum naphtha,  and  on  recrystallization  are  obtained  pure.  The  remain- 
ing mother-liquors  which  on  concentration  do  not  yield  any  crystals, 
are  evaporated,  and  the  oily  matter  reserved  for  a  subsequent  ope- 
ration. 
