Difference between revisions of "Silver"

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'''Silver''' is a chemical element and transitional metal, with the symbol Ag and atomic number 47. Silver has the highest electrical and thermal conductivity of any metal and is the most reflective metal.
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{{Infobox element
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<!-- top -->
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|image name=Fine_Silver.jpg
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|image alt=
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|image size=
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|image name comment= One troy ounce of fine silver
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|image name 2=
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|image alt 2=
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|image size 2=
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|image name 2 comment=
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<!-- General properties -->
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|name= Silver
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|symbol= Ag
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|pronounce=
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|pronounce ref=
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|pronounce comment=
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|pronounce 2=
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|alt name=
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|alt names=
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|allotropes=
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|appearance= Lustrous silvery metal
 +
<!-- Periodic table -->
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|above= [[Copper|Cu]]
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|below= [[Gold|Au]]
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|left= [[Palladium]]
 +
|right= [[Cadmium]]
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|number= 47
 +
|atomic mass= 107.8682(2)
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|atomic mass 2=
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|atomic mass ref=
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|atomic mass comment=
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|series= Transition metal
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|series ref=
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|series comment=
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|series color=
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|group=
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|group ref=
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|group comment= 11
 +
|period= 5
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|period ref=
 +
|period comment=
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|block= d
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|block ref=
 +
|block comment=
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|electron configuration= [Kr] 4d<sup>10</sup> 5s<sup>1</sup>
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|electron configuration ref=
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|electron configuration comment=
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|electrons per shell= 2, 8, 18, 18, 1
 +
|electrons per shell ref=
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|electrons per shell comment=
 +
<!-- Physical properties -->
 +
|physical properties comment=
 +
|color= Silvery white
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|phase= Solid
 +
|phase ref=
 +
|phase comment=
 +
|melting point K= 1234.93
 +
|melting point C= 961.78
 +
|melting point F= 1763.2
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|melting point ref=
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|melting point comment=
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|boiling point K= 2435
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|boiling point C= 2162
 +
|boiling point F= 3924
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|boiling point ref=
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|boiling point comment=
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|sublimation point K=
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|sublimation point C=
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|sublimation point F=
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|sublimation point ref=
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|sublimation point comment=
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|density gplstp=
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|density gplstp ref=
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|density gplstp comment=
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|density gpcm3nrt= 10.49
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|density gpcm3nrt ref=
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|density gpcm3nrt comment=
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|density gpcm3nrt 2=
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|density gpcm3nrt 2 ref=
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|density gpcm3nrt 2 comment=
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|density gpcm3nrt 3=
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|density gpcm3nrt 3 ref=
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|density gpcm3nrt 3 comment=
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|density gpcm3mp= 9.320
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|density gpcm3mp ref=
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|density gpcm3mp comment=
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|density gpcm3bp=
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|density gpcm3bp ref=
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|density gpcm3bp comment=
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|molar volume=
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|molar volume unit =
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|molar volume ref=
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|molar volume comment=
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|triple point K=
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|triple point kPa=
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|triple point ref=
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|triple point comment=
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|triple point K 2=
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|triple point kPa 2=
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|triple point 2 ref=
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|triple point 2 comment=
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|critical point K=
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|critical point MPa=
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|critical point ref=
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|critical point comment=
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|heat fusion= 11.28
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|heat fusion ref=
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|heat fusion comment=
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|heat fusion 2=
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|heat fusion 2 ref=
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|heat fusion 2 comment=
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|heat vaporization= 254
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|heat vaporization ref=
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|heat vaporization comment=
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|heat capacity= 25.350
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|heat capacity ref=
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|heat capacity comment=
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|heat capacity 2=
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|heat capacity 2 ref=
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|heat capacity 2 comment=
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|vapor pressure 1=1283
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|vapor pressure 10=1413
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|vapor pressure 100=1575
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|vapor pressure 1 k=1782
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|vapor pressure 10 k=2055
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|vapor pressure 100 k=2433
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|vapor pressure ref=
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|vapor pressure comment=
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|vapor pressure 1 2=
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|vapor pressure 10 2=
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|vapor pressure 100 2=
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|vapor pressure 1 k 2=
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|vapor pressure 10 k 2=
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|vapor pressure 100 k 2=
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|vapor pressure 2 ref=
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|vapor pressure 2 comment=
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<!-- Atomic properties -->
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|atomic properties comment=
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|oxidation states= −2, −1, '''1''', 2, 3, 4
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|oxidation states ref=
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|oxidation states comment=
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|electronegativity= 1.93
 +
|electronegativity ref=
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|electronegativity comment=
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|ionization energy 1=731.0
 +
|ionization energy 1 ref=
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|ionization energy 1 comment=
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|ionization energy 2=2070
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|ionization energy 2 ref=
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|ionization energy 2 comment=
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|ionization energy 3=3361
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|ionization energy 3 ref=
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|ionization energy 3 comment=
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|number of ionization energies=
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|ionization energy ref=
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|ionization energy comment=
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|atomic radius=144
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|atomic radius ref=
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|atomic radius comment=
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|atomic radius calculated=
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|atomic radius calculated ref=
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|atomic radius calculated comment=
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|covalent radius=145±5
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|covalent radius ref=
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|covalent radius comment=
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|Van der Waals radius=172
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|Van der Waals radius ref=
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|Van der Waals radius comment=
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<!-- Miscellanea -->
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|crystal structure=
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|crystal structure prefix=
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|crystal structure ref=
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|crystal structure comment= ​face-centered cubic (fcc)
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|crystal structure 2=
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|crystal structure 2 prefix=
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|crystal structure 2 ref=
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|crystal structure 2 comment=
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|speed of sound=
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|speed of sound ref=
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|speed of sound comment=
 +
|speed of sound rod at 20=
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|speed of sound rod at 20 ref=
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|speed of sound rod at 20 comment=
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|speed of sound rod at r.t.= 2680
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|speed of sound rod at r.t. ref=
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|speed of sound rod at r.t. comment=
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|thermal expansion=
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|thermal expansion ref=
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|thermal expansion comment=
 +
|thermal expansion at 25=18.9
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|thermal expansion at 25 ref=
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|thermal expansion at 25 comment=
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|thermal conductivity=429
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|thermal conductivity ref=
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|thermal conductivity comment=
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|thermal conductivity 2=
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|thermal conductivity 2 ref=
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|thermal conductivity 2 comment=
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|thermal diffusivity=174
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|thermal diffusivity ref=
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|thermal diffusivity comment=
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|electrical resistivity=
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|electrical resistivity unit prefix=
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|electrical resistivity ref=
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|electrical resistivity comment=
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|electrical resistivity at 0=
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|electrical resistivity at 0 ref=
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|electrical resistivity at 0 comment=
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|electrical resistivity at 20=15.87
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|electrical resistivity at 20 ref=
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|electrical resistivity at 20 comment=
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|band gap=
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|band gap ref=
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|band gap comment=
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|Curie point K=
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|Curie point ref=
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|Curie point comment=
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|magnetic ordering= Diamagnetic
 +
|magnetic ordering ref=
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|magnetic ordering comment=
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|tensile strength=
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|tensile strength ref=
 +
|tensile strength comment=
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|Young's modulus=83
 +
|Young's modulus ref=
 +
|Young's modulus comment=
 +
|Shear modulus=30
 +
|Shear modulus ref=
 +
|Shear modulus comment=
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|Bulk modulus=100
 +
|Bulk modulus ref=
 +
|Bulk modulus comment=
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|Poisson ratio=0.37
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|Poisson ratio ref=
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|Poisson ratio comment=
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|Mohs hardness=2.5
 +
|Mohs hardness ref=
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|Mohs hardness comment=
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|Mohs hardness 2=
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|Mohs hardness 2 ref=
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|Mohs hardness 2 comment=
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|Vickers hardness=251
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|Vickers hardness ref=
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|Vickers hardness comment=
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|Brinell hardness=
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|Brinell hardness ref=
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|Brinell hardness comment=
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|CAS number= 206–250
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|CAS number ref=
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|CAS number comment=
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<!-- History -->
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|naming=
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|predicted by=
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|prediction date ref=
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|prediction date=
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|discovered by=
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|discovery date ref=
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|discovery date= before 5000 BC
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|first isolation by=
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|first isolation date ref=
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|first isolation date=
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|discovery and first isolation by=
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|named by=
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|named date ref=
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|named date=
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|history comment label=
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|history comment=
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<!-- Isotopes -->
 +
|isotopes=
 +
|isotopes comment=
 +
|engvar=
 +
}}
 +
{{stub}}
 +
'''Silver''' is a chemical element and transitional metal, with the symbol '''Ag''' and atomic number 47. Silver has the highest electrical and thermal conductivity of any metal and is the most reflective metal.
  
 
==Properties==
 
==Properties==
 
===Chemical===
 
===Chemical===
−
Silver is resistant to many acids, such as halogen acids and [[sulfuric acid]], but will slowly dissolve in nitric acid forming [[silver nitrate]], reaction sped up by heating. It's stable in pure air and water, but tarnishes when it is exposed to air or water containing [[ozone]] or [[hydrogen sulfide]], in case of the latter it forms a black layer of [[silver sulfide]] which can be cleaned off with dilute [[hydrogen peroxide]] or [[hydrochloric acid]]. This phenomenon can be used as an indicator of air quality. Silver can be attacked by strong oxidizers, such as [[potassium dichromate]] or [[potassium permanganate]], in the presence of [[potassium bromide]].
+
Silver is resistant to many acids, such as organic acids, halogen acids and cold [[sulfuric acid]], but will slowly dissolve in conc. [[nitric acid]] forming [[silver nitrate]], reaction sped up by heating.
  
−
[[Silver fulminate]] (AgCNO) is a powerful touch sensitive explosive, that has little value in chemistry because it's extremely sensitive to shock, heat, static electricity. It is however used in bang snaps.
+
: 3 Ag + 4 HNO<sub>3</sub> (cold and diluted) → 3 AgNO<sub>3</sub> + 2 H<sub>2</sub>O + [[nitric oxide|NO]]
 +
: Ag + 2 HNO<sub>3</sub> (hot and concentrated) → AgNO<sub>3</sub> + H<sub>2</sub>O + NO<sub>2</sub>
  
−
Silver halides are photosensitive and are known for their ability to record a latent image, that can later be developed chemically, process that made photography possible.
+
[[Perchloric acid]] will also react with silver metal, more so when hot<ref>Gmelins Handbuch der anorganischen Chemie, Silber Teil B1, 8th edition 1971, p. 508ff</ref>, as does hot sulfuric acid.
 +
 
 +
: 2 Ag + 3 HClO<sub>4</sub> → 2 AgClO<sub>4</sub> + HClO<sub>3</sub> + H<sub>2</sub>O
 +
: 2 Ag + 2 H<sub>2</sub>SO<sub>4</sub> → Ag<sub>2</sub>SO<sub>4</sub> + SO<sub>2</sub> + 2 H<sub>2</sub>O
 +
 
 +
It's stable in pure air and water, but tarnishes when it is exposed to air or water containing [[ozone]] or [[hydrogen sulfide]], in case of the latter it forms a black layer of [[silver sulfide]] which can be cleaned off with dilute [[hydrogen peroxide]] or [[hydrochloric acid]]. This phenomenon can be used as an indicator of air quality. Silver can be attacked by strong oxidizers, such as [[potassium dichromate]] or [[potassium permanganate]], in the presence of [[potassium bromide]].
 +
 
 +
In the presence of air, or even hydrogen peroxide, silver dissolves readily in aqueous solutions of cyanide.<ref>Chemistry of the Elements 2nd Edition, by N. N. Greenwood (Author), A. Earnshaw (Author), 1997</ref>
 +
 
 +
[[Silver fulminate]] (AgCNO) is a powerful touch sensitive explosive obtained from silver metal, that has little value in chemistry because it's extremely sensitive to shock, heat, static electricity. It is however used in bang snaps.
 +
 
 +
Silver halides, such as [[silver chloride]], are photosensitive and are known for their ability to record a latent image, that can later be developed chemically, process that made photography possible.
  
 
===Physical===
 
===Physical===
−
Silver is soft, white metal. It has the highest electrical conductivity of any known metal and compound (except superconductors) and highest thermal conductivity.
+
Silver is soft, white metal. It has the highest electrical conductivity of any known metal and compound (except superconductors) and highest thermal conductivity of all known metals. It melts at 961.78 °C and boils at 2162 °C. It is a dense metal (10.49 g/cm<sup>3</sup>), though slightly less dense than [[lead]].
  
 
==Availability==
 
==Availability==
−
Silver can be obtained from certain coins and jewelries, as an alloy, so purification might be required. US quarters and dimes made before 1964 were made of a 90% silver and 10% copper alloy. Nickels made between 1942-1945 ("War nickels") contain 35% silver, the rest being copper and manganese.<ref>https://www.youtube.com/watch?v=lLNf-vRKTmU</ref> However it's illegal to destroy money to obtain the metal from them.
+
Silver can be obtained from certain coins and jewelries, as an alloy, so purification might be required. US quarters and dimes made before 1964 were made of a 90% silver and 10% copper alloy. Nickels made between 1942-1945 ("War nickels") contain 35% silver, the rest being copper and manganese.<ref>https://www.youtube.com/watch?v=lLNf-vRKTmU</ref> However it may be illegal to destroy local money in order to obtain the metal from them, depending where you live.
  
−
Silver is also found in many contacts from various electronic devices, such as switches, circuit breakers, relays, as a sintered alloy, usually with [[nickel]], [[copper]] and [[tungsten]] or [[tungsten carbide]]. There is no standard mixture, sometimes other elements are also present such as [[cadmium]], which makes extraction difficult due to its toxicity. The specific gravity varies among the contacts, some can be as low as 6 g/cm<sup>3</sup>, while other may reach 10 g/cm<sup>3</sup>. Determining the exact percentage of silver presents challenges.
+
Silver is also found in many contacts from various electronic devices, such as switches, circuit breakers, relays, as a sintered alloy, usually with [[nickel]], [[copper]] and [[tungsten]] or [[tungsten carbide]]. There is no standard mixture, sometimes other elements are also present such as [[cadmium]], which makes extraction difficult due to its toxicity. The specific gravity varies among the contacts, some can be as low as 6 g/cm<sup>3</sup>, while other may reach 10 g/cm<sup>3</sup>. Determining the exact percentage of silver from electrical contacts presents challenges.
  
 
Tin-silver-copper solders also contain small amounts of silver in their composition.
 
Tin-silver-copper solders also contain small amounts of silver in their composition.
  
 
Various other electronics that contain appreciable amounts of silver:
 
Various other electronics that contain appreciable amounts of silver:
−
*Mylar sheets from old keyboards contain silver. You can get around 4 g of silver from around 25-26 mylars.
+
*Mylar sheets from old keyboards contain silver. You can get between 1-4 g of silver from around 25 mylars, depending on when the keyboard was made.
−
*Coin and button batteries (found on motherboards and in small electronics) often use silver oxide and zinc to generate power electrochemically. When these batteries are fully spent, the silver oxide inside has been reduced to silver metal, which can be carefully collected and purified. Another option is simply to dissolve the contents of the battery in [[nitric acid]] and precipitate the silver by adding [[copper]], comparatively a much more reactive metal, to a solution of silver nitrate or another soluble silver salt.
+
*Coin and button batteries (found on motherboards and in small electronics) often use silver oxide and zinc to generate power electrochemically. When these batteries are fully spent, the silver oxide inside has been reduced to silver metal, which can be carefully collected and purified. Another option is simply to dissolve the contents of the battery in [[nitric acid]] and precipitate the silver by adding [[copper]], comparatively a much more reactive metal, to a solution of silver nitrate or another reducing agent.
−
*Certain monolithic capacitors may contain silver instead of palladium
+
*Certain monolithic capacitors may contain silver instead of [[palladium]]. Some may not even have palladium.
 
*Varistor disks tend to be coated with a small amount of silver
 
*Varistor disks tend to be coated with a small amount of silver
  
−
Lastly, silver can also be bought as ingots and bars, thought it's price will vary depending on the market.
+
Note that extracting silver (and other precious metals) from electronics may or may not be legal depending on your jurisdiction. Consult the law or your lawyer before you start doing any precious metal refining.
  
−
==Preparation==
+
Lastly, silver can also be bought as ingots and bars, thought its price will vary depending on the market.
−
Silver can be obtained by reducing it's salt with a reducing agent, such as ascorbic acid.
+
 
 +
Silver can be found in nature in native form, as nuggets, often as a natural alloy. It requires a lot of work to obtain any significant amounts of Ag metal this way, and silver extraction may not be legal, depending on the country. Many former silver mines tend to still be property of the previous company, so it's illegal to mine other private properties.
 +
 
 +
==Isolation==
 +
Silver can be obtained by reducing its salt with a reducing agent, such as ascorbic acid. Silver metal precipitates as a very fine powder, which is then filtered, dried and melted if desired to keep the silver in bulk.
  
 
It can also be obtained by chemical purification of silver alloys used to make jewelry and coins. This is a process done in several steps.
 
It can also be obtained by chemical purification of silver alloys used to make jewelry and coins. This is a process done in several steps.
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* The powdered pure silver is washed with water to remove the remnants of acid.
 
* The powdered pure silver is washed with water to remove the remnants of acid.
  
−
If you are sure that copper is the only contaminant, a simpler process can be used. Do not add the hydroxide, evaporate the solution and crystallize the nitrate mixture and heat it to the temperature of 280 degrees. Copper nitrate will decompose, and silver nitrate won't, and it will be available for extraction with water, recrystallization and decomposition under 500 degrees to produce elemental silver.
+
If you are sure that copper is the only contaminant, a simpler process can be used. Do not add the hydroxide, evaporate the solution and crystallize the nitrate mixture and heat it to the temperature of 280 degrees. Copper nitrate will decompose, and silver nitrate won't, and it will be available for extraction with water, recrystallization and decomposition under 500 degrees to produce elemental silver. Filtering the silver powder from the reaction product is not easy, as due to its density it tends to compact, which prevents the removal of water, while also retaining copper nitrate/oxide.
  
 
==Projects==
 
==Projects==
−
*[[Silver nitrate]]
+
*Make [[silver nitrate]]
−
*[[Silver fulminate]]
+
*Make [[silver fulminate]]
−
*[[Silver aceltylide]]
+
*Make [[silver acetylide]]
−
*[[Silver azide]]
+
*Make [[silver azide]]
 
*Electrolytic silver cell
 
*Electrolytic silver cell
−
*Silver crystal growing, caused by insertion of a well-cleaned [[copper]] object such as wire into [[silver nitrate]] solution. The end product is a plant-like growth of silver crystals in a blue solution([[copper(II) nitrate]]).
+
*Silver crystal growing, caused by insertion of a well-cleaned [[copper]] object such as wire into [[silver nitrate]] solution. The end product is a plant-like growth of silver crystals in a blue solution ([[copper(II) nitrate]]).
 
*Anti-bacterial surfaces
 
*Anti-bacterial surfaces
  
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===Storage===
 
===Storage===
−
Silver does not require special disposal, though if stored in sulfide polluted air, it will form a dark layer. The layer can be removed with hydrogen peroxide.  
+
Silver does not require special disposal, though if stored in sulfide polluted air, it will form a dark layer. The layer can be removed by washing the silver metal with hydrogen peroxide. To limit this, you can keep the silver in a closed bottle or bag.
 +
 
 +
Silver jewelry should be kept in a safe.
  
 
===Disposal===
 
===Disposal===
−
Due to its high price, it's best to try to recycle the silver.
+
Due to its high price and scarcity, it's best to try to recycle all the silver.
  
 
==References==
 
==References==
 
<references/>
 
<references/>
 
===Relevant Sciencemadness threads===
 
===Relevant Sciencemadness threads===
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=11530 Silver Precipitation from Silver Nitrite]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=11473 silver]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=63640 Tin, Lead, and Silver from Solder]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=65686 Is it silver? -> Cutlery plating]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=14772 Silver Tarnish Cleaning]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=4159 Queries on the silver mirror process]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=64235 Deposit Silver on PVC]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=13330 Silver purification]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=10814 Separation of Lead and Silver?]
 +
*[https://www.sciencemadness.org/whisper/viewthread.php?tid=22653 Silver salts to elemental silver?]
  
 
[[Category:Elements]]
 
[[Category:Elements]]
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[[Category:Precious metals]]
 
[[Category:Precious metals]]
 
[[Category:D-block]]
 
[[Category:D-block]]
 +
[[Category:Noble metals]]
 +
[[Category:Minerals]]
 +
[[Category:Coinage metals]]

Latest revision as of 16:36, 4 April 2023

Silver,  47Ag
Fine Silver.jpg
One troy ounce of fine silver
General properties
Name, symbol Silver, Ag
Appearance Lustrous silvery metal
Silver in the periodic table
Cu
↑
Ag
↓
Au
Palladium ← Silver → Cadmium
Atomic number 47
Standard atomic weight (Ar) 107.8682(2)
Group, block 11; d-block
Period period 5
Electron configuration [Kr] 4d10 5s1
per shell
 2, 8, 18, 18, 1
Physical properties
Silvery white
Phase Solid
Melting point 1234.93 K ​(961.78 °C, ​1763.2 °F)
Boiling point 2435 K ​(2162 °C, ​3924 °F)
Density near r.t. 10.49 g/cm3
when liquid, at  9.320 g/cm3
Heat of fusion 11.28 kJ/mol
Heat of 254 kJ/mol
Molar heat capacity 25.350 J/(mol·K)
 pressure
Atomic properties
Oxidation states −2, −1, 1, 2, 3, 4
Electronegativity Pauling scale: 1.93
energies 1st: 731.0 kJ/mol
2nd: 2070 kJ/mol
3rd: 3361 kJ/mol
Atomic radius empirical: 144 pm
Covalent radius 145±5 pm
Van der Waals radius 172 pm
Miscellanea
Crystal structure ​​face-centered cubic (fcc)
Speed of sound thin rod 2680 m/s (at )
Thermal expansion 18.9 µm/(m·K) (at 25 °C)
Thermal conductivity 429 W/(m·K)
Thermal diffusivity 174 mm2/s (at 300 K)
Electrical resistivity 15.87 Ω·m (at 20 °C)
Magnetic ordering Diamagnetic
Young's modulus 83 GPa
Shear modulus 30 GPa
Bulk modulus 100 GPa
Poisson ratio 0.37
Mohs hardness 2.5
Vickers hardness 251 MPa
CAS Registry Number 206–250
History
Discovery before 5000 BC
· references
Stub.png This article is a stub. Please help Sciencemadness Wiki by expanding it, adding pictures, and improving existing text.

Silver is a chemical element and transitional metal, with the symbol Ag and atomic number 47. Silver has the highest electrical and thermal conductivity of any metal and is the most reflective metal.

Properties

Chemical

Silver is resistant to many acids, such as organic acids, halogen acids and cold sulfuric acid, but will slowly dissolve in conc. nitric acid forming silver nitrate, reaction sped up by heating.

3 Ag + 4 HNO3 (cold and diluted) → 3 AgNO3 + 2 H2O + NO
Ag + 2 HNO3 (hot and concentrated) → AgNO3 + H2O + NO2

Perchloric acid will also react with silver metal, more so when hot[1], as does hot sulfuric acid.

2 Ag + 3 HClO4 → 2 AgClO4 + HClO3 + H2O
2 Ag + 2 H2SO4 → Ag2SO4 + SO2 + 2 H2O

It's stable in pure air and water, but tarnishes when it is exposed to air or water containing ozone or hydrogen sulfide, in case of the latter it forms a black layer of silver sulfide which can be cleaned off with dilute hydrogen peroxide or hydrochloric acid. This phenomenon can be used as an indicator of air quality. Silver can be attacked by strong oxidizers, such as potassium dichromate or potassium permanganate, in the presence of potassium bromide.

In the presence of air, or even hydrogen peroxide, silver dissolves readily in aqueous solutions of cyanide.[2]

Silver fulminate (AgCNO) is a powerful touch sensitive explosive obtained from silver metal, that has little value in chemistry because it's extremely sensitive to shock, heat, static electricity. It is however used in bang snaps.

Silver halides, such as silver chloride, are photosensitive and are known for their ability to record a latent image, that can later be developed chemically, process that made photography possible.

Physical

Silver is soft, white metal. It has the highest electrical conductivity of any known metal and compound (except superconductors) and highest thermal conductivity of all known metals. It melts at 961.78 °C and boils at 2162 °C. It is a dense metal (10.49 g/cm3), though slightly less dense than lead.

Availability

Silver can be obtained from certain coins and jewelries, as an alloy, so purification might be required. US quarters and dimes made before 1964 were made of a 90% silver and 10% copper alloy. Nickels made between 1942-1945 ("War nickels") contain 35% silver, the rest being copper and manganese.[3] However it may be illegal to destroy local money in order to obtain the metal from them, depending where you live.

Silver is also found in many contacts from various electronic devices, such as switches, circuit breakers, relays, as a sintered alloy, usually with nickel, copper and tungsten or tungsten carbide. There is no standard mixture, sometimes other elements are also present such as cadmium, which makes extraction difficult due to its toxicity. The specific gravity varies among the contacts, some can be as low as 6 g/cm3, while other may reach 10 g/cm3. Determining the exact percentage of silver from electrical contacts presents challenges.

Tin-silver-copper solders also contain small amounts of silver in their composition.

Various other electronics that contain appreciable amounts of silver:

  • Mylar sheets from old keyboards contain silver. You can get between 1-4 g of silver from around 25 mylars, depending on when the keyboard was made.
  • Coin and button batteries (found on motherboards and in small electronics) often use silver oxide and zinc to generate power electrochemically. When these batteries are fully spent, the silver oxide inside has been reduced to silver metal, which can be carefully collected and purified. Another option is simply to dissolve the contents of the battery in nitric acid and precipitate the silver by adding copper, comparatively a much more reactive metal, to a solution of silver nitrate or another reducing agent.
  • Certain monolithic capacitors may contain silver instead of palladium. Some may not even have palladium.
  • Varistor disks tend to be coated with a small amount of silver

Note that extracting silver (and other precious metals) from electronics may or may not be legal depending on your jurisdiction. Consult the law or your lawyer before you start doing any precious metal refining.

Lastly, silver can also be bought as ingots and bars, thought its price will vary depending on the market.

Silver can be found in nature in native form, as nuggets, often as a natural alloy. It requires a lot of work to obtain any significant amounts of Ag metal this way, and silver extraction may not be legal, depending on the country. Many former silver mines tend to still be property of the previous company, so it's illegal to mine other private properties.

Isolation

Silver can be obtained by reducing its salt with a reducing agent, such as ascorbic acid. Silver metal precipitates as a very fine powder, which is then filtered, dried and melted if desired to keep the silver in bulk.

It can also be obtained by chemical purification of silver alloys used to make jewelry and coins. This is a process done in several steps.

  • The coin, ring or another object made of a silver alloy is dissolved in nitric acid. The reaction should be done under a fume hood or outdoors, because of nitrogen dioxide.
  • The solution at the end of the reaction is of a bluish-green color, because it contains a mixture of copper, silver and other metal nitrates.
  • Sodium hydroxide is added into the solution. All dissolved metals precipitate in the form of hydroxides.
  • The precipitate is removed from the solution and dried.
  • The dried precipitate is heated to the temperature of 280-300 degrees Celsius. This temperature is enough to decompose the silver (I) oxide, but not enough to decompose the oxides of copper, nickel or whatever other metals are there. After heating, the precipitate turns into a mixture of powdered elemental silver and various oxides.
  • The calcinated powder is treated with hydrochloric acid, which dissolves all oxides but does not attack elemental silver. It is the only substance left in the powder.
  • The powdered pure silver is washed with water to remove the remnants of acid.

If you are sure that copper is the only contaminant, a simpler process can be used. Do not add the hydroxide, evaporate the solution and crystallize the nitrate mixture and heat it to the temperature of 280 degrees. Copper nitrate will decompose, and silver nitrate won't, and it will be available for extraction with water, recrystallization and decomposition under 500 degrees to produce elemental silver. Filtering the silver powder from the reaction product is not easy, as due to its density it tends to compact, which prevents the removal of water, while also retaining copper nitrate/oxide.

Projects

Handling

Safety

Silver metal has antiseptic properties and does not react with the organism. Silver compounds are harmful, and in large doses, silver compounds or colloids will deposit in various body tissues, leading to argyria, which results in a blue-grayish pigmentation of the skin.

Storage

Silver does not require special disposal, though if stored in sulfide polluted air, it will form a dark layer. The layer can be removed by washing the silver metal with hydrogen peroxide. To limit this, you can keep the silver in a closed bottle or bag.

Silver jewelry should be kept in a safe.

Disposal

Due to its high price and scarcity, it's best to try to recycle all the silver.

References

  1. ↑ Gmelins Handbuch der anorganischen Chemie, Silber Teil B1, 8th edition 1971, p. 508ff
  2. ↑ Chemistry of the Elements 2nd Edition, by N. N. Greenwood (Author), A. Earnshaw (Author), 1997
  3. ↑ https://www.youtube.com/watch?v=lLNf-vRKTmU

Relevant Sciencemadness threads

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