Aluminum  unites  with  the  other  metals,
forming  allots,  of  which  some  promise  to  be
of  great  value  in  the  arts.  An  alloy  of  100
parts  of  aluminum  with  5  parts  of  silver  may
be  worked  liko  the  pure  metal,  but  is  harder
and  susceptible  of  n  finer  polish,  whilst  its
property  of  not  being  affected  by  sulphuretted
hydrogen  and  acids  remains  unimpaired;  even
3|  of  silver  is  said  to  be  sufficient  to  impart  to
it  the  full  brilliance  and  colour  of  pure  silver.
An  alloy  containing  10§  of  gold  is  softer  and
scarcely  so  malleable  as  the  pure  metal.  With
85  of  iron,  or  lOJ  of  copper,  it  still  remains
tough  and  malleable;  but  a  larger  proportion
of  either  of  these  metals  renders  it  brittle.
The  presence  of  2  or  3  J-  of  zinc  destroys  its
ductility  and  malleability,  and  also  impairs  its
colour  and  lustre;  whilst  less  than  even  ij  of
•  bismuth  renders  it  brittle  in  a  high  degree,
Small  quantities  of  aluminum  added  to  other
metals  change  their  properties  in  a  very  re-
markable manner.  Thus,  copper  alloyed  with
10§  of  aluminum  has  the  colour  and  brilliancy
of  gold,  is  harder  than  bronze,  very  malleable,
and  may  be  worked  at  high  temperatures  easier
than  the  best  varieties  of  iron ;  and  with  20^
is  quite  white,  and  closely  resembles  silver.
With  more  than  12;  of  aluminum  the  alloy  is

VOL.   I.
harder,  but  brittle.  The  alloy  formed  of  100
parts  of  silver  with  5  parts  ol  aluminum  ii
as  hard  as  the  silver  of  our  coinage,  whilst
the  other  properties  of  the  latter  metal  remain
unaltered.
