ON  SILICIUM  AND  TITANIUM. 
441 
the  greater  part  of  the  alkaline  chloride,  two  kinds  of  products 
are  obtained,  which  vary  according  to  the  temperature  and  the 
nature  of  the  flux. 
In  the  first  place  the  graphitoid  silicium  already  described  by 
me*  as  being  obtained  from  the  fonte  of  aluminium,  may  be  pro- 
duced ;  fused  silicium  is  also  obtained  in  the  midst  of  a  gangue 
which  resists  the  action  of  heat ;  it  is  then  frequently  crystallized. 
Crystallized  silicium  has  much  resemblance  in  color  with  spe- 
cular iron  ore  when  a  little  iridescent.  Its  form  cannot  be  exactly 
measured,  the  faces  of  the  crystals  being  always  curved ;  but 
the  form  presents  so  close  a  resemblance  to  those  of  the  diamond, 
that  this  comparison  has  been  made  immediately  by  all  the 
mineralogists  to  whom  I  have  shown  it.  In  this  state  silicium 
cuts  glass. 
The  analysis  of  the  crystals  which  accompanied  the  specimen 
exhibited  furnished  the  following  results  ; — 100  silicium  gave  205 
of  silica ;  calculation  requires  209.  The  small  quantity  of 
matter  which  was  wanting  also  contained  silica  and  iron,  but  in 
proportions  which  might  be  neglected.  Thus  silicium,  like  carbon, 
beside  which  it  has  been  placed  in  the  series  of  metalloids,  is 
capable  of  assuming  three  distinct  forms : — 
1.  The  silicium  of  Berzelius,  which  represents  ordinary  carbon. 
2.  Graphitoid  silicium,  which  corresponds  with  graphite,  and 
is  obtained  under  the  same  circumstances  as  artificial  graphite. 
3.  Crystallized  silicium,  which  is  the  analogue  of  the  diamond. 
Silicium  consequently  differs  from  the  metals  in  every  respect. 
I  also  exhibit  some  fused  silicium,  which  has  been  extracted 
from  diflerent  gangues.  I  cannot,  however,  state  exactly  either 
the  temperature,  which  was  very  high,  employed  in  this  new  ex- 
periment, or  the  mode  of  preparation  which  is  most  proper  for 
attaining  a  certain  result.  I  must  observe  only  that  silicium  takes 
up  iron,  wherever  it  exists,  even  in  vessels  in  common  porcelain, 
which  it  corrodes  in  a  singular  manner,  f    In  preparing  silicium, 
*Chem.  Gaz.,  No.  287,  Oct.  2,  1854,  p.  362. 
-j-It  reacts  upon  alumina,  at  least  in  the  presence  of  bases,  furnishing 
vitreous  products,  which  appear  to  me  to  be  new,  and  which  I  am  at  present 
engaged  in  analysing.  The  vessels  which  I  prefer  are  crucibles  of  coke, 
calcined  and  immersed  whilst  still  hot  in  boiling  muriatic  acid.  After 
remaining  for  some  time  in  the  acid,  and  being  repeatedly  washed,  these 
crucibles  are  very  good. 
