342  .  ON  BORON. 
boracic  acid  and  alumina,  and  the  other  metallic  and  cavernous, 
of  an  iron-gray  color,  beset  with  little  crystals  of  boron  ;  it  is 
aluminium,  impregnated  throughout  with  crystallized  boron.  All 
the  metallic  portion  is  treated  with  a  moderately  concentrated 
boiling  solution  of  soda,  which  dissolves  the  aluminium ;  then 
with  boiling  muriatic  acid,  which  removes  the  iron  ;  and  lastly, 
with  a  mixture  of  hydrofluoric  and  nitric  acids,  to  extract  the 
traces  of  silicium,  which  the  soda  may  have  left  mixed  with  the 
boron.  The  boron  is  not  pure,  however  ;  it  contains  laminae  of 
aluminium,  which  may  be  extracted  mechanically,  but  cannot  be 
separated  from  the  boron  by  any  chemical  process. 
The  vitreous  matter,  when  boiled  with  water,  gives  a  large 
quantity  of  boracic  acid  and  a  gelatinous  matter,  which,  is  nearly 
pure  alumina.  The  spontaneous  separation  of  alumina  from 
boracic  acid  is  in  accordance  with  Rose's  observations  on  the 
action  of  water  upon  the  borates  with  insoluble  bases. 
2.  Graphitoid  Boron. — Aluminium  dissolves  but  little  boron. 
Thus  it  is  usually  obtained  only  in  small  quantity  in  this  new 
form,  when  an  alloy  of  boron  and  aluminium  is  dissolved  in  the 
way  already  described  for  the  preparation  of  graphitoid  silicium. 
A  little  is  obtained  in  the  preceding  experiment,  and  it  is  easily 
separated  from  the  crystallized  boron  from  the  facility  with 
which  it  may  be  suspended  in  water.  Graphitoid  boron  may 
also  be  easily  produced  by  treating  fluoborate  of  potash  with 
aluminium,  and  adding  as  a  flux  a  mixture  of  equal.equivalents 
of  the  chlorides  of  potassium  and  sodium.  Small  ingots  of  boride 
of  aluminium  are  obtained,  and  these,  when  dissolved  in  muriatic 
acid,  deposit  the  boron  in  its  second  modification.  This  consists 
of  spangles,  which  are  often  hexagonal;  they  are  slightly  reddish, 
and  have  exactly  the  form  and  brilliancy  of  natural  graphite  and 
graphitoid  silicium.    It  is  completely  opake. 
3.  Amorphous  Boron,  or  Boron  of  Gay-Lussac  and  Thenard. 
— This  is  also  produced  in  the  experiment  which  yields  crystal- 
lized boron ;  it  is  sufficient  for  this  purpose  that  a  small  globule 
of  aluminium  should  be  in  contact  with  a  great  mass  of  boracic 
acid.  The  reaction  then  takes  place  rapidly  ;  the  aluminium  can- 
not dissolve  the  boron  as  fast  as  it  is  separated,  and  after  the 
action  of  soda  and  acids  a  bright  chocolate-brown  substance  is 
obtained,  having  all  the  properties  assigned  by  Gay-Lussac, 
