AmDe°cU,ril9arm'}     Contribution  to  the  Knowledge  of  Boron.  603 
ii,  p.  209)  found  that  in  place  of  potassium  or  sodium,  magnesium 
could  be  used  to  advantage  in  the  last  method. 
On  the  advice  of  Prof.  L.  Gatterrnann,  I  took  up  the  reduction  by 
means  of  magnesium,  using  in  place  of  potassium  borofluoride  the 
cheaper  borax.  This  was  employed  in  the  form  of  powdered  borax 
glass  because  the  water  of  crystallization  otherwise  present  would 
have  an  injurious  effect  on  the  reaction. 
Without  going  into  details  as  to  the  experiments  made  with  the 
idea  of  finding  the  best  proportion  of  the  reagents  to  be  used,  I  will 
simply  give  the  one  which  was  found  to  be  the  best.  The  bottom  of 
a  hessian  crucible  was  covered  with  the  powdered  borax  glass,  on  this 
an  intimate  mixture  of  two  parts  borax  and  one  part  magnesium 
powder  was  packed,  so  as  to  drive  out  as  much  air  as  possible,  and 
this  was  covered  by  about  half  an  inch  of  powdered  borax  glass,  which 
is  to  fill  the  crucible.  The  lid  is  then  fastened  down  with  moist  clay 
and  the  whole  subjected  to  the  heat  of  a  well-drawing  charcoal  fur- 
nace, the  crucible  being  surrounded  by  the  fuel,  which  is  allowed  to 
burn  down  once.  After  cooling,  the  crucible  is  broken  and  the  pro- 
duct finely  pulverized.  The  powder  is  extracted  with  boiling  water, 
and,  after  cooling,  thrown  in  small  portions  into  cooled  diluted  hydro- 
chloric acid  and  allowed  to  remain  for  four  or  five  hours,  after  which 
it  is  filtered  off  and  subjected  to  the  action  of  concentrated  hydro- 
chloric acid  for  about  two  hours.  The  powder  is  then  filtered  off, 
washed  with  water  and  dried  either  by  the  heat  of  a  water  bath  or 
by  the  following  method :  The  water  is  replaced  with  alcohol,  this  in 
turn  by  ether,  and  this  allowed  to  evaporate  at  the  temperature  of 
the  room.  The  boron  thus  obtained  is  by  no  means  pure,  but 
answers  perfectly  well  for  the  preparation  of  its  halogen  derivatives. 
Boron  trichloride. — The  first  method  to  be  found  in  literature  is  that 
of  Berzelius  (Pogg.  Ann.,  1824,  ii,  p.  147)  who  states  that  amorphous 
boron  which  has  been  dried  in  a  vacuum  ignites  in  an  atmosphere  of 
chlorine  at  ordinary  temperatures,  while  boron  which  has  been  heated 
reacts  only  at  higher  temperatures.  Some  decades  later  Wohler  and 
Deville  (I.  c.)  showed  that  the  same  takes  place  in  hydrochloric  acid 
gas  ;  the  reaction,  however,  must  be  completed  at  higher  temperatures. 
They  also  found  that  by  the  action  of  boron  on  mercuric  chloride,  lead 
chloride,  or  silver  chloride  this  compound  was  likewise  obtained. 
The  method  which  has  been  used  up  to  the  present  for  the  prepara- 
tion of  the  chloride  is  that  of  Dumas  (Ann.  Chim.  Phys.,  1826,  xxxi, 
