604  Contribution  to  the  Knowledge  of  Boron.  {AmbJe°cU,Ji8^9arm* 
p.  466  ;  xxxiii,  376),  who  allowed  chlorine  to  pass  in  a  tube  over  a 
heated  mixture  of  powdered  melted  boric  acid  and  charcoal. 
It  seemed  to  be  of  interest  to  ascertain  how  the  boron  prepared  by 
the  above  method  would  behave  towards  chlorine.  The  apparatus 
which  was  used  was  the  following  :  A  hard  glass  tube,  as  used  for  com- 
bustions, about  4  to  8  inches  longer  than  the  combustion  furnace  to  be 
used,  is  drawn  out  at  one  end  and  bent  almost  at  right  angles.  This 
part  is  attached  to  a  Peligot's  tube,  which  is  surrounded  by  a  freezing 
mixture  of  ice  and  salt.  All  the  necessary  joints  are  made  by  means 
of  smooth  and  closely-fitting  corks.  The  air-dry  boron  is  loosely 
spread  in  the  combustion  tube,  so  that  it  is  one-fourth  inch  in  thickness 
all  through ;  and  as  the  boron  must  be  thoroughly  dry  the  water  is 
driven  out  by  heating  in  a  stream  of  hydrogen,  also  allowing  it  to 
cool  in  the  same.  Carbonic  acid  cannot  be  used,  as  boron  reduces  it 
completely  to  carbon  monoxide,  as  noticed  by  Lorenz  (Ann.  Chem., 
1889,  ccxlvii,  p.  226).  After  the  tube  has  cooled  the  hydrogen  is  forced 
out  by  a  stream  of  dry  air,  and  tHe  larger  end  of  the  tube  then  con- 
nected with  a  chlorine  generator.  The  chlorine  is  prepared  from  man- 
ganese dioxide  and  hydrochloric  acid,  and  best  regulated  so  that  a  slow 
but  steady  stream  is  obtained.  The  whole  apparatus  is  filled  with 
washed  and  dried  chlorine  gas  before  heat  is  applied,  sufficient  for  pro- 
ducing a  slight  glow  in  the  tube.  A  liquid  having  the  color  of  chlo- 
rine gas  condenses  in  the  Peligot's  tube,  which  is  best  connected  with 
a  good  drawing  chimney,  as  some  of  the  trichloride  goes  through 
uncondensed.  The  color  of  the  liquid  is  due  to  dissolved  chlorine, 
which  is  removed  by  shaking  the  liquid  with  mercury  in  a  sealed  tube, 
which  can  also  be  used  for  distilling.  After  the  liquid  has  become 
perfectly  colorless,  which  takes  about  two  days,  the  tube  is  opened 
and  by  means  of  a  closely-fitting  cork  a  narrow  glass  tube,  twice  bent 
at  right  angles,  is  attached.  The  one  arm  of  the  tube  which  is  used 
as  a  condenser  is  to  be  about  20  inches  long  and  projects  to  the  bot- 
tom of  the  receiving  vessel,  which  is  surrounded  by  a  freezing  mixture 
of  ice  and  salt.  The  best  receiver  is  a  wide  glass  tube  about  25  inches 
long  and  about  5  inches  below  the  orifice  drawn  out,  so  that  the  con- 
densing tube  just  moves  freely  in  the  opening.  The  distillation  is 
best  carried  on  by  means  of  warm  water,  very  slowly,  so  as  not  to 
lose  too  much  of  the  chloride — this  boiling  at  18°  C.  The  yield  of 
the  chloride  by  this  process  is  as  follows  :  By  using  8  gms.  of  magne- 
sium powder  for  reduction  the  boron  gave  15  gms.  of  the  chloride,  the 
theoretical  yield  being  26  gms. 
