266.  Characteristic  Reactions.  —  The  presence  of  copper  in
a  solution  may  be  readily  detected,  not  only  by  ammonia  as  in-
dicated above,  but  also  by  the  action  of  polished  iron  (a  needle,
for  example),  which,  in  a  feebly  acid  solution,  soon  becomes
covered  with  a  red  metallic  coating.     Copper  ores,  when  mixed
with  fluxes,  are  readily  reduced  on  charcoal  before  the  blow-
pipe, and  this  is  one  of  the  best  means  of  recognizing  such
compounds.
267.  Uses.  —  Besides  the  numerous  uses  of  the  metal  itself,
copper  is  employed  in  the  arts  still  more  extensively  when
alloyed  with  other  metals.     The  varieties  of  brass  and  yellow
metal  are  alloys  of  copper  and  zinc  in  different  proportions*


3.32  MERCUEY.  [§  268.
while  bronze,  bell-metal,  gun-metal,  and  speculum-metal  are  all
essentially  alloys  of  copper  and  tin.  Several  of  the  compounds
of  copper  are  much  used  as  paints.
268.  MERCURY.     Hg  =  200.  —  Dyad.     This  element  is
not  widely  disseminated,  but  its  ores  are  abundant  in  a  few  lo-
calities, of  which  the  most  noted  are  Idria  in  Austria,  Almaden
in  Spain,  New  Almaden  in  California,  and  Huancavelica  in  Peru.
The  ores  at  all  these  localities  consist  chiefly  of  Cinnabar,  UgS,
but  they  frequently  contain  a  small  quantity  of  the  metal  in  the
native  state.     They  are  easily  smelted,  the  sulphur  of  the  ore
serving  as  fuel.     The  assorted  ores  are  arranged  in  layers  in
kilns  of  peculiar  construction,  and  the  mass  kindled  with  brush-
wood.    As  the  sulphur  burns  away,  the  mercury  is  volatilized,
and  the  products  thus  formed  are  passed  through  earthen  pipes
("  aludels  ")  or  brick  chambers,  which  condense  the  mercury
vapor,  while  the  S02  gas  escapes  into  the  atmosphere.
