Difference between revisions of "Iodine"

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[[File:DU8fKVG-1-.jpg|thumb|256px|Iodine sublimating in a fume hood.]]
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{{Infobox element
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'''Iodine''' is the element with the symbol I and atomic number 53. It is a reactive [[halogen]] which is volatile and has many uses in inorganic and organic chemistry.
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<!-- top -->
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|image name=Iodine vapors hotplate.jpg
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|image alt=
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|image size=300
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|image name comment=Iodine sublimating in a fume hood.
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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=Iodine
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|symbol=I
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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 metallic gray (solid)<br>Violet (gas)
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<!-- Periodic table -->
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|above=[[Bromine|Br]]
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|below=[[Astatine]]
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|left=[[Tellurium]]
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|right=[[Xenon]]
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|number=53
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|atomic mass=126.90447(3)
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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=
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|series ref=
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|series comment=
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|series color=
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|group=17
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|group ref=
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|group comment=17
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|period=5
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|period ref=
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|period comment=
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|block=p
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|block ref=
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|block comment=
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|electron configuration=[Kr] 4d<sup>10</sup> 5s<sup>2</sup> 5p<sup>5</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, 7
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|electrons per shell ref=
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|electrons per shell comment=
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<!-- Physical properties -->
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|physical properties comment=
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|color=Metallic gray
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|phase=Solid
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|phase ref=
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|phase comment=
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|melting point K=386.85
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|melting point C=113.7
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|melting point F=236.66
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|melting point ref=
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|melting point comment=
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|boiling point K=457.4
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|boiling point C=184.3
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|boiling point F=363.7
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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=4.933
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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=
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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=386.65
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|triple point kPa=12.1
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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=819
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|critical point MPa=11.7
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|critical point ref=
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|critical point comment=
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|heat fusion=15.52
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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=41.57
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|heat vaporization ref=
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|heat vaporization comment=
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|heat capacity=54.44
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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=260
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|vapor pressure 10=282
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|vapor pressure 100=309
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|vapor pressure 1 k=342
 +
|vapor pressure 10 k=381
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|vapor pressure 100 k=457
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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=7, 6, 5, 4, 3, 1, −1 ​
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|oxidation states ref=
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|oxidation states comment=(a strongly acidic oxide)
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|electronegativity=2.66
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|electronegativity ref=
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|electronegativity comment=
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|ionization energy 1=1008.4
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|ionization energy 1 ref=
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|ionization energy 1 comment=
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|ionization energy 2=1845.9
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|ionization energy 2 ref=
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|ionization energy 2 comment=
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|ionization energy 3=3180
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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=140
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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=139±3
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|covalent radius ref=
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|covalent radius comment=
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|Van der Waals radius=198
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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= Orthorhombic
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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=
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|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.=
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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=
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|thermal expansion at 25=
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|thermal expansion at 25 ref=
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|thermal expansion at 25 comment=
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|thermal conductivity=0.449
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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=
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|thermal diffusivity ref=
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|thermal diffusivity comment=
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|electrical resistivity=1.3×10<sup>7</sup>
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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=
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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
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|magnetic ordering ref=
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|magnetic ordering comment=
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|tensile strength=
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|tensile strength ref=
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|tensile strength comment=
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|Young's modulus=
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|Young's modulus ref=
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|Young's modulus comment=
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|Shear modulus=
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|Shear modulus ref=
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|Shear modulus comment=
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|Bulk modulus=7.7
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|Bulk modulus ref=
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|Bulk modulus comment=
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|Poisson ratio=
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|Poisson ratio ref=
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|Poisson ratio comment=
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|Mohs hardness=
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|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=
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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=7553-56-2
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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=
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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=Bernard Courtois (1811)
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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 -->
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|isotopes=
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|isotopes comment=
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|engvar=
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}}
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'''Iodine''' is the element with the symbol '''I''' and atomic number 53. It is a reactive [[halogen]] which is volatile and has many uses in inorganic and organic chemistry.
 +
 
 +
Unlike the other halogens, iodine is solid at standard conditions and does not sublime rapidly, thus can be handled much safer.
  
 
==Properties==
 
==Properties==
 
===Physical===
 
===Physical===
−
[[File:Iodine beaker.JPG|thumb|293x293px|Metallic crystals of iodine encrusting the inside of a beaker.]]
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Iodine can be seen in the form of royal dark purple crystals, or in a gas in a lighter color. It is most commonly found as a silvery metallic looking chemical. Iodine, like other halogens, has its own unique smell, somewhat similar to [[chlorine]], or described as being "clean". Contrary to some sources, iodine will melt if heated, though it tends to sublime a lot. This can be done very easy by using high heat or hot concentrated [[sulfuric acid]].
−
Iodine can be seen in the form of royal dark purple crystals, or in a gas in a lighter color. It is most commonly found as a silvery metallic looking chemical. Iodine, like other halogens, has its own unique smell, somewhat similar to [[chlorine]], or described as being "clean".
+
  
 
===Chemical===
 
===Chemical===
 
Iodine is not very soluble in water, but is very soluble in a solution of sodium or [[potassium iodide]] in water. When dissolved like this, the solution has a color from light yellow to dark orange, to almost black brown. This change in color and solubility is due to the formation of the triiodide(I<sub>3</sub><sup>-</sup>) ion. If reacted while in water with a sufficient reducing agent, such as [[phosphorus]] or [[hydrogen sulfide]], iodine is converted to hydrogen iodide, which dissolves in solution as [[hydroiodic acid]]. Iodine possesses some metallic properties, despite being a [[Halogen]].
 
Iodine is not very soluble in water, but is very soluble in a solution of sodium or [[potassium iodide]] in water. When dissolved like this, the solution has a color from light yellow to dark orange, to almost black brown. This change in color and solubility is due to the formation of the triiodide(I<sub>3</sub><sup>-</sup>) ion. If reacted while in water with a sufficient reducing agent, such as [[phosphorus]] or [[hydrogen sulfide]], iodine is converted to hydrogen iodide, which dissolves in solution as [[hydroiodic acid]]. Iodine possesses some metallic properties, despite being a [[Halogen]].
  
−
==Preparation/Availability==
+
==Availability/Isolation==
−
[[File:GoodCrystals.JPG|thumb|220x220px|Metallic iodine prepared by melting in H<sub>2</sub>SO<sub>4</sub>]]
+
Elemental iodine is sold by chemical suppliers, but it's not easy to get hold of.
−
Iodine can be isolated by acidifying a soluble iodide (I<sup>-</sup>) solution to form [[hydroiodic acid]], adding an oxidizing agent like [[hydrogen peroxide]] to precipitate insoluble iodine, and purifying by sublimation. Adding
+
  
−
concentrated [[sulfuric acid]] or [[nitric acid]] will produce iodine directly. Wet iodine can be dried by melting under concentrated sulfuric acid. Iodine is not easily purchased in the United States and other countries that tightly control drug precursors, as iodine is often used in the clandestine manufacture of methamphetamine.
+
Iodine is best extracted from iodine tinctures, though you will need large amounts of such tincture to obtain useful amounts of iodine. Iodine can be isolated by acidifying a soluble iodide (I<sup>-</sup>) solution to form [[hydroiodic acid]], adding an oxidizing agent like [[hydrogen peroxide]] to precipitate insoluble iodine, and purifying by sublimation. Adding concentrated [[sulfuric acid]] or [[nitric acid]] will produce iodine directly. Wet iodine can be dried by melting under concentrated sulfuric acid.
 +
 
 +
Another convenient source of iodine is seaweed, which contains a few percentages of iodine. To extract the iodine, you will need lots of dry seaweed, a few kg minimum. Old seaweed mattresses tend to be a good source. You can also collect it directly from beaches if it's permitted (check the local law before you do anything). Dry the seaweed then burn it in a container until it turns into ash. Add some water to the seaweed ash, then filter the suspension to separate the soluble part, which includes the iodine. Concentrate the solution until it crystals begin to form. To extract the iodine simply add conc. sulfuric acid, followed by conc. hydrogen peroxide. Dry and purify the resulting iodine. Keep in mind that seaweed also contains bromine and lots of chlorine (from sodium bromide and sodium chloride aka sea salt) and this may contaminate you iodine.<ref>https://www.youtube.com/watch?v=jmWB1Sl2uzE</ref>
  
 
===Legality===
 
===Legality===
 +
Iodine is not easily purchased in the United States and other countries that tightly control drug precursors, as iodine is often used in the clandestine manufacture of methamphetamine.
 +
 
Iodine is a controlled substance in many countries due to its use in producing illicit drugs, and while possession of iodine itself may not be a crime, its presence in a lab may be used to build a case against an innocent amateur chemist.
 
Iodine is a controlled substance in many countries due to its use in producing illicit drugs, and while possession of iodine itself may not be a crime, its presence in a lab may be used to build a case against an innocent amateur chemist.
 +
 +
However, in most countries elemental iodine can be purchased freely, with no restrictions.
  
 
==Projects==
 
==Projects==
−
*Make [[Nitrogen Triiodide|nitrogen triiodide]]
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*Make [[nitrogen triiodide]]
 +
*Make organoiodine compounds ([[methyl iodide]], [[ethyl iodide]], [[iodoform]], etc.)
 
*Anhydrous metal iodides
 
*Anhydrous metal iodides
 +
*Make [[hydrogen iodide]] and [[hydroiodic acid]]
 
*Activating magnesium for [[Grignard reagent]] prep
 
*Activating magnesium for [[Grignard reagent]] prep
 +
*Make purple smoke (dangerous)
 +
*Iodoform test (detecting aldehydes and ketones)
  
 
==Handling==
 
==Handling==
 
===Safety===
 
===Safety===
 
Iodine, like other halogens, is toxic in large quantities and its vapors should not be inhaled. Objects stained with iodine solution or with solid iodine on them should not be brought inside or left out, as any iodine will sublimate given time. Iodine stains can be cleaned with a solution of [[sodium thiosulfate]].
 
Iodine, like other halogens, is toxic in large quantities and its vapors should not be inhaled. Objects stained with iodine solution or with solid iodine on them should not be brought inside or left out, as any iodine will sublimate given time. Iodine stains can be cleaned with a solution of [[sodium thiosulfate]].
 +
 +
Iodine is corrosive to most common metals, which is why it should only be handled with glass or plastic tools.
  
 
===Storage===
 
===Storage===
Line 34: Line 317:
  
 
===Disposal===
 
===Disposal===
−
Iodine can be neutralized by reacting it with thiosulfate.
+
Iodine can be neutralized by reacting it with a reducing agent, like sodium or potassium thiosulfate.
 +
 
 +
==Gallery==
 +
<gallery widths="200" position="center" columns="4" orientation="none">
 +
Iodine beaker.jpg|Metallic crystals of iodine encrusting the inside of a beaker
 +
Iodine Good Crystals.jpg|Metallic iodine prepared by melting in H<sub>2</sub>SO<sub>4</sub>
 +
</gallery>
  
 
==References==
 
==References==
 
<references />
 
<references />
 
===Relevant Sciencemadness threads===
 
===Relevant Sciencemadness threads===
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=1869 Finally! Povidone iodine extraction (this one works way better than Rhodiums extraction method)]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=14229 Iodine from seaweed]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=10887 Iodine preparation for who needs it]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=19745 Synthesis of Iodine from KI and sulfuric acid question.]
 +
*[http://www.sciencemadness.org/talk/viewthread.php?tid=6200 Liquid Iodine]
  
 
[[Category:Elements]]
 
[[Category:Elements]]
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[[Category:Nonmetals]]
 
[[Category:Nonmetals]]
 
[[Category:P-block]]
 
[[Category:P-block]]
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[[Category:DEA List I chemicals]]

Latest revision as of 15:21, 23 December 2021

Iodine,  53I
Iodine vapors hotplate.jpg
Iodine sublimating in a fume hood.
General properties
Name, symbol Iodine, I
Appearance Lustrous metallic gray (solid)
Violet (gas)
Iodine in the periodic table
Br
↑
I
↓
Astatine
Tellurium ← Iodine → Xenon
Atomic number 53
Standard atomic weight (Ar) 126.90447(3)
Group, block 17; p-block
Period period 5
Electron configuration [Kr] 4d10 5s2 5p5
per shell
 2, 8, 18, 18, 7
Physical properties
Metallic gray
Phase Solid
Melting point 386.85 K ​(113.7 °C, ​236.66 °F)
Boiling point 457.4 K ​(184.3 °C, ​363.7 °F)
Density near r.t. 4.933 g/cm3
Triple point 386.65 K, ​12.1 kPa
Critical point 819 K, 11.7 MPa
Heat of fusion 15.52 kJ/mol
Heat of 41.57 kJ/mol
Molar heat capacity 54.44 J/(mol·K)
 pressure
Atomic properties
Oxidation states 7, 6, 5, 4, 3, 1, −1 ​ ​(a strongly acidic oxide)
Electronegativity Pauling scale: 2.66
energies 1st: 1008.4 kJ/mol
2nd: 1845.9 kJ/mol
3rd: 3180 kJ/mol
Atomic radius empirical: 140 pm
Covalent radius 139±3 pm
Van der Waals radius 198 pm
Miscellanea
Crystal structure ​Orthorhombic
Thermal conductivity 0.449 W/(m·K)
Electrical resistivity 1.3×107 Ω·m
Magnetic ordering Diamagnetic
Bulk modulus 7.7 GPa
CAS Registry Number 7553-56-2
Discovery and first isolation Bernard Courtois (1811)
· references

Iodine is the element with the symbol I and atomic number 53. It is a reactive halogen which is volatile and has many uses in inorganic and organic chemistry.

Unlike the other halogens, iodine is solid at standard conditions and does not sublime rapidly, thus can be handled much safer.

Properties

Physical

Iodine can be seen in the form of royal dark purple crystals, or in a gas in a lighter color. It is most commonly found as a silvery metallic looking chemical. Iodine, like other halogens, has its own unique smell, somewhat similar to chlorine, or described as being "clean". Contrary to some sources, iodine will melt if heated, though it tends to sublime a lot. This can be done very easy by using high heat or hot concentrated sulfuric acid.

Chemical

Iodine is not very soluble in water, but is very soluble in a solution of sodium or potassium iodide in water. When dissolved like this, the solution has a color from light yellow to dark orange, to almost black brown. This change in color and solubility is due to the formation of the triiodide(I3-) ion. If reacted while in water with a sufficient reducing agent, such as phosphorus or hydrogen sulfide, iodine is converted to hydrogen iodide, which dissolves in solution as hydroiodic acid. Iodine possesses some metallic properties, despite being a Halogen.

Availability/Isolation

Elemental iodine is sold by chemical suppliers, but it's not easy to get hold of.

Iodine is best extracted from iodine tinctures, though you will need large amounts of such tincture to obtain useful amounts of iodine. Iodine can be isolated by acidifying a soluble iodide (I-) solution to form hydroiodic acid, adding an oxidizing agent like hydrogen peroxide to precipitate insoluble iodine, and purifying by sublimation. Adding concentrated sulfuric acid or nitric acid will produce iodine directly. Wet iodine can be dried by melting under concentrated sulfuric acid.

Another convenient source of iodine is seaweed, which contains a few percentages of iodine. To extract the iodine, you will need lots of dry seaweed, a few kg minimum. Old seaweed mattresses tend to be a good source. You can also collect it directly from beaches if it's permitted (check the local law before you do anything). Dry the seaweed then burn it in a container until it turns into ash. Add some water to the seaweed ash, then filter the suspension to separate the soluble part, which includes the iodine. Concentrate the solution until it crystals begin to form. To extract the iodine simply add conc. sulfuric acid, followed by conc. hydrogen peroxide. Dry and purify the resulting iodine. Keep in mind that seaweed also contains bromine and lots of chlorine (from sodium bromide and sodium chloride aka sea salt) and this may contaminate you iodine.[1]

Legality

Iodine is not easily purchased in the United States and other countries that tightly control drug precursors, as iodine is often used in the clandestine manufacture of methamphetamine.

Iodine is a controlled substance in many countries due to its use in producing illicit drugs, and while possession of iodine itself may not be a crime, its presence in a lab may be used to build a case against an innocent amateur chemist.

However, in most countries elemental iodine can be purchased freely, with no restrictions.

Projects

Handling

Safety

Iodine, like other halogens, is toxic in large quantities and its vapors should not be inhaled. Objects stained with iodine solution or with solid iodine on them should not be brought inside or left out, as any iodine will sublimate given time. Iodine stains can be cleaned with a solution of sodium thiosulfate.

Iodine is corrosive to most common metals, which is why it should only be handled with glass or plastic tools.

Storage

Elemental iodine is very difficult to store properly, as it tends to sublime at ambient temperatures and its vapors will escape the storage bottle, and stain the environment where it's stored. Sealing the bottle with parafilm or teflon tape will reduce the escaping iodine vapors. Do NOT use aluminium or any other metal foil, as it will corrode.

A more permanent way is to store the iodine in a sealed glass ampoule.

Disposal

Iodine can be neutralized by reacting it with a reducing agent, like sodium or potassium thiosulfate.

Gallery

  • Metallic crystals of iodine encrusting the inside of a beaker

  • Metallic iodine prepared by melting in H2SO4

References

  1. ↑ https://www.youtube.com/watch?v=jmWB1Sl2uzE

Relevant Sciencemadness threads

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