ANOMALIES  PRESENTED  BY  ALUMINIUM. 
843 
Thenard,  and  Berzelius  to  the  amorphous  boron  with  which  they 
were  acquainted. 
When  amorphous  boron  is  collected  on  a  filter,  all  that  remains 
adhering  to  the  latter  when  well  dried,  burns  with  remarkable 
facility  and  brilliancy  when  the  paper  is  set  on  fire.  Graphitoid 
boron,  on  the  contrary,  resists  the  heat  produced  by  the  com- 
bustion of  paper. 
From  these  facts  it  appears  that  boron  should  be  placed  still 
nearer  than  silicium  to  carbon  Chem.  Graz.,  May,  1857,  from 
Comptes  Rendus,  Dee.  8,  1856. 
NOTE  ON  THE  ANOMALIES  PRESENTED  BY  ALUMINIUM. 
By  C.  Tissier. 
Relation  between  the  Density  and  Alter  abilit y . — Hitherto  the 
least  oxidizable  metals  have  been  amongst  the  heaviest,  such  as 
mercury,  silver,  gold,  and  platinum  ;  nevertheless,  aluminium, 
the  density  of  which  is  only  2.56,  is  the  least  alterable  of  all  the 
ordinary  metals,  after  silver,  gold,  and  platinum. 
Relation  between  the  Atomic  Weight  and  the  Alter  ability . — 
In  general  the  metals  are  more  alterable  the  lower  their  atomic 
weight;  nevertheless,  the  atom  of  aluminium,  the  alterability  of 
which  is  so  small,  only  weighs  14 ;  that  is  to  say,  it  has  the 
lowest  atomic  weight  of  all  the  ordinary  metals.  It  is  the  half 
of  that  of  iron,  which  is  28. 
Relation  between  the  Density  and  the  Physical  Properties  of 
Metals. — We  do  not  know  of  any  other  body  of  so  little  density, 
which  possesses  like  aluminium,  the  hardness,  malleability,  te- 
nacity, conductibility,  and  sonorousness  charcteristic  of  what  is 
called  a  metal. 
Aluminium  and  Thenard' 8  Classification. — According  to 
Sainte-Claire  Deville,  aluminium  does  not  decompose  water;*  it 
should  therefore  be  ranged  at  least  in  the  fourth  section,  accord- 
ing to  Thenard's  classification,  and  yet  its  oxide  (alumina)  is  not 
reducible  by  hydrogen  and  carbon,  or  even  by  sodium  or  potas- 
sium. 
*  We  admit  that  it  absorbs  oxygen  from  the  air  at  a  very  high  tempera- 
ture. 
