ON  BORON. 
341 
Pulverulent  boron,  which  it  is  almost  impossible  to  otsain 
pure  by  the  process  of  Berzelius,  was  fused  by  M.  Despretz  with 
the  pile.  With  the  heat  of  the  oxhydrogen  flame,  no  percepti- 
ble fusion  took  place  with  crystallized  boron.  Crystallized 
boron,  when  strongly  heated,  resists  the  action  of  oxygen  ;  it 
becomes  oxidized  at  the  temperature  at  which  the  diamond  burns, 
but  a  little  stratum  of  boracic  acid,  which  forms  upon  its  surface 
and  is  easily  seen,  prevents  the  extension  of  the  action. 
Chlorine,  on  the  contrary,  acts  with  remarkable  energy  upon 
boron,  which  becomes  red-hot  in  an  atmosphere  of  this  gas,  and 
is  converted  into  gaseous  chloride  of  boron  ;  it  is  difficult  to  get 
chlorine  sufficiently  dry  to  avoid  the  production  of  a  little  vapor 
in  this  experiment,  and  a  little  boracic  acid  is  deposited,  arising 
from  the  water  and  air  contained  in  the  chlorine.  Crystallized 
boron  burns  without  residue  ;  the  apparent  inflation  of  the  crys- 
tals, characteristic  of  the  combustion  of  the  diamond  in  oxygen, 
is  also  manifested. 
When  heated  with  the  blowpipe  between  two  plates  of  platinum, 
it  immediately  causes  the  fusion  of  the  metal  in  consequence  of 
the  formation  of  a  boride.*  No  acids,  whether  pure  or  mixed, 
have  any  action  upon  boron,  either  cold  or  hot ;  at  a  red  heat 
bisulphate  of  potash  converts  it  into  boracic  acid,  with  evolution 
of  sulphurous  acid. 
Boiling  concentrated  caustic  soda  does  not  change  it ;  but 
monohydrated  soda  and  carbonate  of  soda  dissolves  it  slowly  at 
a  red  heat.  Nitrate  of  potash  does  not  appear  to  act  upon  crys- 
tallized boron  at  this  temperature;  it  is  therefore  the  most  un- 
alterable of  all  simple  bodies. 
It  is  prepared  by  fusing  together  in  a  charcoal  crucible  80 
grms.  of  aluminium  in  large  fragments,  and  100  grms.  of  frag- 
ments of  fused  boracic  acid.  The  charcoal  crucible  is  luted  into 
a  good  black-lead  crucible,  and  the  whole  put  into  a  blast-furnace 
capable  of  easily  fusing  pure  nickel.  The  temperature  is  kept 
at  its  maximum  for  about  five  hours,  care  being  taken  to  clear 
the  bars  of  all  ashes.  When  cold,  the  crucible  is  broken,  and 
two  distinct  strata  are  found  in  it, — one  vitreous,  composed  of 
*  Very  curious  alloys  of  boron  with  platinum  and  palladium  have  been 
obtained. 
