On/?-* 
ON  ALUMINIUM.  125  / 
'JCf  p3g 
125  / 
object  to  dissolve  out  the  metals  which  darken  the  color  of  alu- 
minium by  their  presence. 
Aluminium  forms  alloys  with  nearly  all  the  metals,  but  those 
which  it  forms  with  silver  and  copper  are  the  most  interesting. 
Five  parts  of  aluminium  with  one  hundred  parts  of  pure  silver 
produce  an  alloy  almost  as  hard  as  a  silver-coin,  which  contains 
about  one-tenth  of  copper,  so  that  sufficient  hardness  can  be 
given  to  silver,  without  introducing  into  it  a  poisonous  or  an 
alterable  metal.  It  has  the  advantage  of  being  worked  like 
silver  in  a  pure  state,  possessing,  however,  greater  hardness,  and 
being  capable  of  a  higher  polish. 
Ten  parts  of  aluminium  and  ninety  parts  of  copper  produce 
an  alloy  of  a  pale  gold  color,  possessing  great  hardness  and 
considerable  malleability ;  its  hardness  is  greater  than  that  of 
bronze,  in  the  proportion  of  fifty-one  to  forty-nine.  It  can  be 
worked  when  warm,  with  the  same  facility  as  the  best  soft  iron. 
Twenty  parts  of  aluminium  and  eighty  of  copper  give  to  the 
alloy  the  color  and  brilliancy  of  fine  gold,  and  at  the  same  time 
sufficient  hardness  to  scratch  the  alloy  of  gold  employed  in  coin, 
without  imparing  in  the  slightest  degree  its  malleability. 
By  an  increase  of  the  per  centage  of  copper  in  alloys  of  alu- 
minium the  alloy  is  rendered  brittle,  showing  that  the  metal 
must  be  either  used  pure  or  alloyed  in  small  quantities  with  the 
copper. 
This  explains  the  peculiar  properties  ascribed  to  it  by  M. 
Regnault  in  his  investigation  on  the  physical  properties  of  the 
aluminium  prepared  by  M.  Deville,  exhibited  at  the  Paris  exhi- 
bition. 
Numerous  experiments  have  been  made  (without  regard  to 
economy  of  manufacture)  to  obtain  the  aluminium  directly  from 
the  oxide  alumina,  or  from  the  fluoride  of  aluminium. 
But  the  results  obtained  by  the  use  of  this  double  chloride  of 
aluminium  and  sodium,  have  fully  demonstrated  that  it  is  the 
most  economical  mode  by  which  to  produce  this  metal.  Theo- 
retically it  requires — 
3-86  Chlorine,  at  6  cts.  per  pound  ....  -23  16-100 
1-86  Alumina,  at  3    «  «         ....    *05  58-100 
5-68  Carbonate  of  soda,  at  4  cts.  per  pound  .      .    -22  72-100 
Total, 
•51  46-100 
