344  ANOMALIES  PRESENTED   BY  ALUMINIUM. 
Aluminium  does  not  decompose  water,  and  it  decomposes  car- 
bonic acid  and  silicic  acid  exactly  in  the  same  way  as  potassium 
or  sodium. 
What  rank  must  be  assigned  to  Aluminium  f — This  metal 
ranks  not  far  from  silver  in  its  action  upon  water  and  oxygen  ; 
near  the  alkaline  metals  in  its  action  upon  silicic,  boracic  and 
carbonic  acids,  and  near  iron  in  its  action  upon  the  metallic 
oxides  ;  in  fact,  it  decomposes  all  the  oxides  which  are  decom- 
posed by  iron,  except  the  oxide  of  zinc.  According  to  this  last 
peculiarity,  aluminium  would  have  less  affinity  for  oxygen  than 
iron,  and  would  range  beside  iron,  but  below  it. 
In  considering  what  place  aluminium  should  occupy  in  the 
electro-chemical  series,  we  find  that  it  precipitates  all  the  metals 
from  their  chlorides  up  to  lead  and  cadmium  inclusive,*  so  that 
it  comes  between  cadmium  and  iron. 
To  sum  up,  until  chemistry  has  made  further  progress,  we  must 
not  hope  to  assign  aluminium  an  exact  place  in  the  classifications. 
However,  as  M.  Sainte-Claire  Deville  has  said,  it  will  certainly 
be  least  out  of  place  by  the  side  of  iron.  We  know,  in  fact,  that 
at  a  high  temperature  iron  also  decomposes  silicic,  boracic  and 
carbonic  acids;  and  if  aluminium  has  not  the  same  action  upon 
oxygen  and  water  as  iron,  it  is,  as  M.  Deville  has  also  observed, 
because  we  do  not  know  an  oxide  of  aluminium  of  the  formula 
R3  O4,  an  oxide  which  iron  always  tends  to  produce  at  a  high 
temperature. 
Lastly,  taking  into  consideration  the  electro-chemical  proper- 
ties, it  is  still  in  the  neighborhood  of  iron  that  aluminium  would 
be  placed. 
The  remarkable  properties  which  distinguish  this  metal  from 
all  others  are  therefore — 
1.  Its  slight  density. 
2.  Its  resistance  to  the  action  of  the  oxyacids  and  sulphur- 
etted compounds,  which  approximates  it  to  gold  and  platinum. 
3.  The  difficulty  with  which  it  enters  into  alloys,  a  property 
which  is  not  shared  by  the  other  malleable  metals  ;  for  iron,  zinc, 
lead,  tin,  copper,  silver,  gold,  and  platinum  are  capable  of  form- 
*  This  observation  is  the  result  of  personal  experiments.  Aluminium 
has  no  action  upon  the  chlorides  of  iron,  zinc,  and  manganese. 
