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{{Distinguish|Potassium chromate}} |
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{{chembox |
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{{chembox |
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| verifiedrevid = 394178870 |
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| verifiedrevid = 406377229 |
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| Name = Potassium dichromate |
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| Name = Potassium dichromate |
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| ImageFile = Potassium-dichromate-sample.jpg |
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| ImageFile = Potassium-dichromate-sample.jpg |
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| ImageName = Potassium dichromate |
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<!-- | ImageSize = 200px --> |
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| ImageName = Potassium dichromate |
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| ImageFile1 = Potassium-dichromate-unit-cell-3D-balls.png |
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| ImageName1 = Unit cell of potassium dichromate |
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| ImageFile1 = Potassium-dichromate-unit-cell-3D-balls.png |
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| ImageName1 = Unit cell of potassium dichromate |
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| IUPACName = Potassium dichromate(VI) |
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| OtherNames = {{ubl|potassium bichromate |
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| IUPACName = Potassium dichromate(VI) |
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|bichromate of potash |
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| OtherNames = Potassium bichromate |
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|dipotassium dichromate |
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| Section1 = {{Chembox Identifiers |
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|dichromic acid, dipotassium salt |
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| CASNo = 7778-50-9 |
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|chromic acid, dipotassium salt |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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|]<ref>{{cite web|url=http://www.epa.gov/osw/hazard/wastetypes/wasteid/inorchem/docs/pot-dich.pdf|title=POTASSIUM DICHROMATE LISTING|publisher=US EPA|date=2015-07-23}}</ref> |
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| ChemSpiderID = 22910 |
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}} |
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| SMILES = ..(=O)(=O)O()(=O)=O |
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| Section1 = {{Chembox Identifiers |
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| StdInChI=1S/2Cr.2K.7O/q;;2*+1;;;;;;2*-1 |
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| CASNo = 7778-50-9 |
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| StdInChIKey = KMUONIBRACKNSN-UHFFFAOYSA-N |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| PubChem = 516855 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| EINECS = 231-906-6 |
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| RTECS = HX7680000 |
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| UNII = T4423S18FM |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| UNNumber = 3288 |
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| ChemSpiderID = 22910 |
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| ChEMBL = 1374101 |
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| SMILES = ..(=O)(=O)O()(=O)=O |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChI =1S/2Cr.2K.7O/q;;2*+1;;;;;;2*-1 |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey = KMUONIBRACKNSN-UHFFFAOYSA-N |
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| PubChem = 24502 |
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| EINECS = 231-906-6 |
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| RTECS = HX7680000 |
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| UNNumber = 3288 |
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}} |
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}} |
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| Section2 = {{Chembox Properties |
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| Section2 = {{Chembox Properties |
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| Formula = K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> |
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| Formula = K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> |
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| MolarMass = 294.185 g/mol |
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| MolarMass = 294.185 g/mol |
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| Appearance = red-orange crystalline solid |
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| Appearance = red-orange crystalline solid |
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| Odor = odorless |
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| Odor = odorless |
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| Density = 2.676 g/cm<sup>3</sup>, solid |
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| Density = 2.676 g/cm<sup>3</sup>, solid |
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| Solubility = 4.9 g/100 ml (0°C) <br> 102 g/100 mL (100 °C) |
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| Solubility = 4.9 g/100 mL (0 °C) <br> 13 g/100 mL (20 °C) <br> 102 g/100 mL (100 °C) |
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| SolubleOther = insoluble in ] |
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| SolubleOther = insoluble in ], ]. |
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| MeltingPt = 398°C |
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| MeltingPtC = 398 |
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| BoilingPt = 500°C ''decomp.'' |
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| BoilingPtC = 500 |
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| BoilingPt_notes = decomposes |
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| RefractIndex = 1.738 |
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}} |
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}} |
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| Section3 = {{Chembox Structure |
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| Section3 = {{Chembox Structure |
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| Coordination = ] (for Cr) |
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| Coordination = ] (for Cr) |
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| CrystalStruct = ] (α-form, <241.6 °C) |
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| CrystalStruct = ] (α-form, <241.6 °C) |
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}} |
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}} |
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| Section4 = {{Chembox Thermochemistry |
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| Section4 = {{Chembox Thermochemistry |
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| DeltaHf = -2033 kJ/mol |
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| DeltaHf = −2033 kJ/mol |
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| Entropy = 291.2 J K<sup>−1</sup> mol<sup>−1</sup> |
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| Entropy = 291.2 J/(K·mol) |
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| HeatCapacity = 219 J/mol<ref>{{cite book|pages=405|isbn=978-3-527-30524-7|date=2002|title=Thermochemical Data of Elements and Compounds|first1=M.|last1=Binnewies|first2=E.|last2=Milke|location=Weinheim|publisher=]|edition=2}}</ref> |
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}} |
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}} |
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| Section7 = {{Chembox Hazards |
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| Section7 = {{Chembox Hazards |
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| ExternalMSDS = |
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| MainHazards= carcinogenic,<ref>Like all compounds of hexavalent chromium, potassium dichromate is carcinogenic</ref> corrosive |
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| EUIndex = 024-002-00-6 |
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| ExternalSDS = |
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| EUClass = Oxidant ('''O''')<br/>]<br/>]<br/>Repr. Cat. 2<br/>Highly toxic ('''T+''')<br/>Harmful ('''Xn''')<br/>Corrosive ('''C''')<br/>Dangerous for the environment ('''N''') |
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| GHSPictograms = {{GHS03}}{{GHS05}}{{GHS06}}{{GHS08}}{{GHS09}}<ref name="sigma">{{Sigma-Aldrich|id=675644|name=Chromium(VI) oxide|accessdate=2014-06-15}}</ref> |
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| RPhrases = {{R45}}, {{R46}}, {{R60}}, {{R61}}, {{R8}}, {{R21}}, {{R25}}, {{R26}}, {{R34}}, {{R42/43}}, {{R48/23}}, {{R50/53}} |
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| HPhrases = |
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| SPhrases = {{S53}}, {{S45}}, {{S60}}, {{S61}} |
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| NFPA-H = 4 |
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| PPhrases = |
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| NFPA-F = 0 |
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| NFPA-H = 4 |
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| NFPA-R = 1 |
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| NFPA-F = 0 |
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| NFPA-O = OX |
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| NFPA-R = 1 |
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| FlashPt = non-flammable |
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| NFPA-S = OX |
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| FlashPt = Non-flammable |
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| LD50 = 25 mg/kg (oral, rat)<ref>{{cite web|url=https://chem.nlm.nih.gov/chemidplus/rn/7778-50-9|title=ChemIDplus - 7778-50-9 - KMUONIBRACKNSN-UHFFFAOYSA-N - Potassium dichromate - Similar structures search, synonyms, formulas, resource links, and other chemical information|first=Michael|last=Chambers}}</ref> |
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}} |
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}} |
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| Section8 = {{Chembox Related |
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| Section8 = {{Chembox Related |
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| OtherAnions = ]<br/>]<br/>] |
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| OtherAnions = ]<br />]<br />] |
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| OtherCations = ]<br/>] |
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| OtherCations = ]<br />] |
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| OtherCpds = ] |
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| OtherCompounds = ] |
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}} |
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}} |
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}} |
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}} |
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'''Potassium dichromate''', K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub>, is a common ] chemical reagent, most commonly used as an ] in various laboratory and industrial applications. As with all ] compounds, it is potentially harmful to health and must be handled and disposed of appropriately. It is a crystalline ionic solid with a very bright, red-orange color. |
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'''Potassium dichromate''', {{chem2|K2Cr2O7|auto=1}}, is a common ] chemical reagent, most commonly used as an ] in various laboratory and industrial applications. As with all ] compounds, it is acutely and chronically harmful to health. It is a crystalline ionic solid with a very bright, red-orange color. The salt is popular in laboratories because it is not ], in contrast to the more industrially relevant salt ].<ref name=Ullmann>Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger, "Chromium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. {{doi|10.1002/14356007.a07_067}}</ref> |
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{{TOC limit|3}} |
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==Chemistry== |
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==Chemistry== |
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Potassium dichromate is an oxidant (oxidizing agent). The reduction half-equation can be seen: |
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===Production=== |
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:Cr<sub>2</sub>O<sub>7</sub><sup>2−</sup>(aq) + 14H<sup>+</sup> + 6e<sup>−</sup> → 2Cr<sup>3+</sup>(aq) + 7H<sub>2</sub>O (E = +1.33 V) |
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Potassium dichromate is usually prepared by the reaction of ] on ]. Alternatively, it can be also obtained from ] by roasting ] ore with ]. It is soluble in water and in the dissolution process it ionizes: |
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{{block indent|K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> → 2 K<sup>+</sup> + {{chem|Cr|2|O|7|2−}}}} |
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{{block indent|{{chem|Cr|2|O|7|2−}} + H<sub>2</sub>O ⇌ 2 {{chem|CrO|4|2−}} + 2 H<sup>+</sup>}} |
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===Reaction=== |
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Potassium dichromate is an oxidising agent in ], and is milder than ]. It is used to ] ]s. It converts primary alcohols into aldehydes and, under more forcing conditions, into carboxylic acids. In contrast, potassium permanganate tends to give carboxylic acids as the sole products. Secondary alcohols are converted into ]s. For example, ] may be prepared by oxidation of ] with acidified dichromate.<ref>{{OrgSynth |title = ''l''-Menthone | author = L. T. Sandborn | collvol = 1 | collvolpages = 340 | prep = cv1p0340}}</ref> Tertiary alcohols cannot be oxidized. |
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In an aqueous solution the color change exhibited can be used to test for distinguishing aldehydes from ketones. Aldehydes reduce dichromate from the +6 to the +3 ], changing color from orange to green. This color change arises because the aldehyde can be oxidized to the corresponding carboxylic acid. A ketone will show no such change because it cannot be oxidized further, and so the solution will remain orange. |
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When heated strongly, it decomposes with the evolution of oxygen. |
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{{block indent|4 K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> → 4 ] + 2 ] + 3 O<sub>2</sub>}} |
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When an ] is added to an orange-red solution containing dichromate ions, a yellow solution is obtained due to the formation of ] ions ({{chem2|CrO4(2-)}}). For example, potassium chromate is produced industrially using ]: |
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In organic chemistry, potassium dichromate is a mild oxidizer compared with ]. It is used to ] ]s. It converts primary alcohols into aldehydes, or into carboxylic acids if heated under ]. In contrast, with permanganate, carboxylic acids are the sole products. Secondary alcohols are converted into ketones — no further oxidation is possible. For example, ] may be prepared by oxidation of ] with acidified dichromate.<ref>{{OrgSynth |title = ''l''-Menthone | author = L. T. Sandborn | collvol = 1 | collvolpages = 340 | prep = cv1p0340}}</ref> Tertiary alcohols are not oxidized by potassium dichromate. |
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{{block indent|K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> + ] → 2 K<sub>2</sub>CrO<sub>4</sub> + CO<sub>2</sub>}} |
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The reaction is reversible. |
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Treatment with cold ] gives red crystals of ] (chromium trioxide, CrO<sub>3</sub>): |
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In an aqueous solution the color change exhibited can be used to test whether an aldehyde or ketone is present. When an aldehyde is present the chromium ions will be reduced from the +6 to the +3 ], changing color from orange to green. This is because the aldehyde can be further oxidized to the corresponding carboxylic acid. A ketone will show no such change because it cannot be oxidized further, and so the solution will remain orange. |
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{{block indent|K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> + 2 H<sub>2</sub>SO<sub>4</sub> → 2 CrO<sub>3</sub> + 2 ] + H<sub>2</sub>O}} |
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On heating with concentrated acid, oxygen is evolved: |
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{{block indent|2 K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> + 8 H<sub>2</sub>SO<sub>4</sub> → 2 ] + 2 ] + 8 H<sub>2</sub>O + 3 O<sub>2</sub>}} |
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==Uses== |
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==Uses== |
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Potassium dichromate has few major applications, as the sodium salt is dominant industrially. The main use is as a precursor to ], used in ].<ref name=Ullmann/><ref>{{Cite journal|title=Footwear dermatitis|author1=M. Saha |author2=C. R. Srinivas |author3=S. D. Shenoy |author4=C. Balachandran |journal=Contact Dermatitis|volume=28|issue=5|pages=260–264|date=May 1993|doi=10.1111/j.1600-0536.1993.tb03428.x|pmid=8365123|s2cid=23159708 }}</ref> |
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===Cleaning=== |
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===Cleaning=== |
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Like other ] compounds (], ]), potassium dichromate may be used to prepare "]", which can be used for cleaning glassware and etching materials. |
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Like other ] compounds (], ]), potassium dichromate has been used to prepare "]" for cleaning glassware and etching materials. Because of safety concerns associated with hexavalent chromium, this practice has been largely discontinued. |
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===Construction=== |
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===Construction=== |
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It is used as an ingredient in ] in which it retards the setting of the mixture and improves its density and texture. This usage commonly causes ] in ].<ref>{{Cite journal|title=Addition of ferrous sulfate to cement and risk of chromium dermatitis among construction workers|author=Pekka Roto, Hannele Sainio, Timo Reunala, Pekka Laippala|journal=Contact Dermatitis|volume=34|issue=1|pages=43–50|date=January 1996|url=http://www.blackwell-synergy.com/doi/abs/10.1111/j.1600-0536.1996.tb02111.x|doi=10.1111/j.1600-0536.1996.tb02111.x|pmid=8789225|postscript=<!--None-->}}</ref> |
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It is used as an ingredient in ] in which it retards the setting of the mixture and improves its density and texture. This usage commonly causes ] in ].<ref>{{Cite journal|title=Addition of ferrous sulfate to cement and risk of chromium dermatitis among construction workers|author1=Pekka Roto |author2=Hannele Sainio |author3=Timo Reunala |author4=Pekka Laippala |journal=Contact Dermatitis|volume=34|issue=1|pages=43–50|date=January 1996|doi=10.1111/j.1600-0536.1996.tb02111.x|pmid=8789225|s2cid=27027304 }}</ref> |
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===Ethanol determination=== |
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===Photography and printing=== |
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In 1839, ] discovered that paper treated with a solution of potassium dichromate was visibly tanned by exposure to sunlight, the discoloration remaining after the potassium dichromate had been rinsed out. In 1852, ] discovered that exposure to ultraviolet light in the presence of potassium dichromate hardened organic ] such as ] and ], making them less soluble. |
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The concentration of ethanol in a sample can be determined by ] with acidified potassium dichromate. Reacting the sample with an excess of potassium dichromate, all ethanol is oxidized to ]: |
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These discoveries soon led to the ], ], and other photographic printing processes based on differential hardening. Typically, after exposure, the unhardened portion was rinsed away with warm water, leaving a thin relief that either contained a pigment included during manufacture or was subsequently stained with a dye. Some processes depended on the hardening only, in combination with the differential absorption of certain dyes by the hardened or unhardened areas. Because some of these processes allowed the use of highly stable dyes and pigments, such as ], prints with an extremely high degree of archival permanence and resistance to fading from prolonged exposure to light could be produced. |
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: C<sub>2</sub>H<sub>5</sub>OH + → CH<sub>3</sub>COOH |
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Dichromated colloids were also used as ]s in various industrial applications, most widely in the creation of metal printing plates for use in photomechanical printing processes. |
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The excess dichromate is determined by titration against ]. Subtracting the amount of excess dichromate from the initial amount, gives the amount of ethanol present. Accuracy can be improved by calibrating the ] solution against a blank. |
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''Chromium intensification'' or ''Photochromos'' uses potassium dichromate together with equal parts of concentrated ] diluted down to approximately 10% v/v to treat weak and thin negatives of black and white photograph roll. This solution reconverts the elemental silver particles in the film to ]. After thorough washing and exposure to ] light, the film can be redeveloped to its end-point yielding a stronger negative which is able to produce a more satisfactory print. |
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One major application for this ] is in old police ] tests. When alcohol vapor makes contact with the yellow dichromate-coated crystals, the ] changes from yellow to green. The degree of the color change is directly related to the level of alcohol in the suspect's breath. |
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A potassium dichromate solution in ] can be used to produce a reversal negative (that is, a positive transparency from a negative film). This is effected by developing a black and white film but allowing the development to proceed more or less to the end point. The development is then stopped by copious washing and the film then treated in the acid dichromate solution. This converts the ] metal to ], a compound that is insensitive to light. After thorough washing and exposure to actinic light, the film is developed again allowing the previously unexposed silver halide to be reduced to silver metal. The results obtained can be unpredictable, but sometimes excellent results are obtained producing images that would otherwise be unobtainable. This process can be coupled with ] so that the end product resembles a negative and is suitable for printing in the normal way. |
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===Leather=== |
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It is used to ] which is used for ].<ref>{{Cite journal|title=Footwear dermatitis|author=M. Saha, C. R. Srinivas, S. D. Shenoy, C. Balachandran|journal=Contact Dermatitis|volume=28|issue=5|pages=260–264|date=May 1993|url=http://www.blackwell-synergy.com/doi/abs/10.1111/j.1600-0536.1993.tb03428.x|doi=10.1111/j.1600-0536.1993.tb03428.x|pmid=8365123|postscript=<!--None-->}}</ref> |
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] compounds have the property of ] animal ]s when exposed to strong light. This quality is used in photographic ]. |
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===Photography=== |
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Potassium dichromate has important uses in ] and in photographic ], where it is used as an oxidizing agent together with a strong mineral acid. |
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In ] a fine screen of bolting silk or similar material is stretched taut onto a frame similar to the way canvas is prepared before painting. A ] sensitized with a dichromate is applied evenly to the taut screen. Once the dichromate mixture is dry, a full-size photographic positive is attached securely onto the surface of the screen, and the whole assembly exposed to strong light – times vary from 3 minutes to a half an hour in bright sunlight – hardening the exposed colloid. When the positive is removed, the unexposed mixture on the screen can be washed off with warm water, leaving the hardened mixture intact, acting as a precise mask of the desired pattern, which can then be printed with the usual ] process. |
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] printing was one of the very first stable photographic printing processes, dating back to about 1850. A solution of ] and potassium dichromate, once applied to paper and dried, will harden when exposed to ultraviolet light. |
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===Analytical reagent=== |
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''Chromium intensification'' or ''Photochromos'' uses potassium dichromate together with equal parts of concentrated ] diluted down to approximately 10% v/v to treat weak and thin negatives of black and white photograph roll. This solution reconverts the elemental silver particles in the film to ]. After thorough washing and exposure to ] light, the film can be redeveloped to its end-point yielding a stronger negative which is able to produce a more satisfactory print. |
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Because it is non-hygroscopic, potassium dichromate is a common reagent in classical "wet tests" in analytical chemistry. |
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====Ethanol determination==== |
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A potassium dichromate solution in ] can be used to produce a reversal negative (i.e., a positive transparency from a negative film). This is effected by developing a black and white film but allowing the development to proceed more or less to the end point. The development is then stopped by copious washing and the film then treated in the acid dichromate solution. This converts the ] metal to ], a compound that is insensitive to light. After thorough washing and exposure to actinic light, the film is developed again allowing the previously unexposed silver halide to be reduced to silver metal. |
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] |
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The concentration of ethanol in a sample can be determined by ] with acidified potassium dichromate. Reacting the sample with an excess of potassium dichromate, all ethanol is oxidized to ]: |
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The results obtained can be unpredictable, but sometimes excellent results are obtained producing images that would otherwise be unobtainable. This process can be coupled with ] so that the end product resembles a negative and is suitable for printing in the normal way. |
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{{block indent|CH<sub>3</sub>CH<sub>2</sub>OH + 2 → CH<sub>3</sub>COOH + H<sub>2</sub>O}} |
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Full reaction of converting ethanol to acetic acid: |
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Cr<sup>VI</sup> compounds have the property of ] animal ]s when exposed to strong light. This quality is used in photographic ]. |
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{{block indent|3 C<sub>2</sub>H<sub>5</sub>OH + 2 K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> + 8 H<sub>2</sub>SO<sub>4</sub> → 3 CH<sub>3</sub>COOH + 2 Cr<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> + 2 K<sub>2</sub>SO<sub>4</sub> + 11 H<sub>2</sub>O}} |
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In ] a fine screen of bolting silk or similar material is stretched taut onto a frame similar to the way canvas is prepared before painting. A ] sensitized with a dichromate is applied evenly to the taut screen. Once the dichromate mixture is dry, a full-size photographic negative is attached securely onto the surface of the screen, and the whole assembly exposed to strong light - typically about half an hour in bright sunlight - hardening the exposed colloid. When the negative is removed, the unexposed mixture on the screen can be washed off with warm water, leaving the hardened mixture intact, acting as a precise mask of the desired pattern, which can then be printed with the usual ] process. |
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The excess dichromate is determined by titration against ]. Adding the amount of excess dichromate from the initial amount, gives the amount of ethanol present. Accuracy can be improved by calibrating the ] solution against a blank. |
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===Silver testing=== |
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One major application for this ] is in old police ] tests. When alcohol vapor makes contact with the orange dichromate-coated crystals, the ] changes from ] orange to Cr(III) green. The degree of the color change is directly related to the level of alcohol in the suspect's breath. |
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====Silver test==== |
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When dissolved in an approximately 35% ] solution it is called Schwerter's solution and is used to test for the presence of various metals, notably for determination of silver purity. Pure silver will turn the solution bright red, ] will turn it dark red, low grade ] (0.800 fine) will turn brown (largely due to the presence of copper which turns the solution brown) and even green for 0.500 silver. |
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When dissolved in an approximately 35% ] solution it is called Schwerter's solution and is used to test for the presence of various metals, notably for determination of silver purity. Pure silver will turn the solution bright red, ] will turn it dark red, low grade ] (0.800 fine) will turn brown (largely due to the presence of copper which turns the solution brown) and even green for 0.500 silver. |
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Brass turns dark brown, copper turns brown, lead and tin both turn yellow while gold and palladium do not change. |
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===Wood treatment=== |
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====Sulfur dioxide test==== |
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Potassium dichromate paper can be used to test for ], as it turns distinctively from orange to green. This is typical of all redox reactions where hexavalent chromium is reduced to trivalent chromium. Therefore, it is not a conclusive test for sulfur dioxide. The final product formed is Cr<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>. |
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Potassium dichromate is used to finish certain types of wood. It brings out the color and grain to a very deep, rich appearance. This is particularly effective on ].<ref>{{cite web | title = Woodworking: Contemporary Headboard | publisher = DIY Network | url = http://www.diynetwork.com/diy/ww_beds_furniture/article/0,,DIY_14438_2274602,00.html | accessdate = 2008-01-28}}</ref> |
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{{block indent|{{chem2 | SO2 + K2Cr2O7 + 3H2SO4 -> K2SO4 + Cr2(SO4)3 + 3 H2O }}}} |
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===Homeopathy=== |
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Potassium dichromate is used as a remedy in ],<ref name="Jouanny">Jacques Jouanny ''The Essentials of Homeopathic Materia Medica''. Bordeaux, France: Delmas, 1980</ref><ref name="Boericke">http://homeoint.org/books/boericmm/index.htm William G Boericke ''Pocket Manual of Homeopathic Materia Medica,'' Philadelphia, Pennsylvania: Boericke & Runyon, 1927</ref> in which it is also called ].<ref></ref> One notable homeopathic product containing potassium dichromate is ], which contains the compound diluted to one ]. |
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===Wood treatment=== |
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Potassium dichromate is used to stain certain types of wood by darkening the tannins in the wood. It produces deep, rich browns that cannot be achieved with modern color dyes. It is a particularly effective treatment on ].<ref>{{cite book |last=Jewitt |first=Jeff |title=Hand-Applied Finishes |year=1997 |publisher=Taunton Press |location=Newtown, Connecticut |isbn=978-1-56158-154-2 |url-access=registration |url=https://archive.org/details/handappliedfinis0000jewi }}</ref> |
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==Natural occurrence== |
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==Natural occurrence== |
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Potassium dichromate occurs naturally as the rare ] ]. It has only been reported as ] fillings in the ] deposits of the ] of ] and in the ] of ].<ref>http://www.mindat.org/min-2433.html Mindat</ref> |
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Potassium dichromate occurs naturally as the rare ] ]. It has only been reported as ] fillings in the ] deposits of the ] of ] and in the ] of ].<ref>{{cite web|url=http://www.mindat.org/min-2433.html|title=Lópezite: Lópezite mineral information and data.}}</ref> |
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==Safety== |
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==Safety== |
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Potassium dichromate is one of the most common causes of chromium ]<ref>{{cite book|title= Diseases of Skin|author=Farokh J. Master|year=2003|url=http://books.google.com/?id=OBAnewDc9CYC|isbn=8170211360|page=223|publisher= B Jain Pub Pvt Ltd|location= New Delhi}}</ref>; chromium is highly likely to induce sensitization leading to dermatitis, especially of the hand and fore-arms, which is chronic and difficult to treat. It is also toxic, with doses of approximately 100 mg/kg being fatal in rabbits and rodents.<ref> HSci project</ref> |
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In 2005–06, potassium dichromate was the 11th-most-prevalent ] in ]s (4.8%).<ref>Zug KA, Warshaw EM, Fowler JF Jr, Maibach HI, Belsito DL, Pratt MD, Sasseville D, Storrs FJ, Taylor JS, Mathias CG, Deleo VA, Rietschel RL, Marks J. Patch-test results of the North American Contact Dermatitis Group 2005–2006. Dermatitis. 2009 May–Jun;20(3):149-60.</ref> |
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Potassium dichromate is one of the most common causes of chromium ];<ref>{{cite book|title= Diseases of Skin|author=Farokh J. Master|year=2003|url=https://books.google.com/books?id=OBAnewDc9CYC|isbn=978-81-7021-136-5|page=223|publisher= B Jain Pub Pvt Ltd|location= New Delhi}}</ref> chromium is highly likely to induce sensitization leading to dermatitis, especially of the hand and forearms, which is chronic and difficult to treat. Toxicological studies have further illustrated its highly toxic nature. With rabbits and rodents, concentrations as low as 14 mg/kg have shown a 50% fatality rate amongst test groups.<ref>{{cite web | title = Potassium dichromate MSDS | publisher = Sigma-Aldrich | url = http://www.sigmaaldrich.com/catalog/product/aldrich/483044 | access-date = 2011-07-20}}</ref> Aquatic organisms are especially vulnerable if exposed, and hence responsible disposal according to the local environmental regulations is advised. |
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As with other Cr<sup>VI</sup> compounds, potassium dichromate is ]ic and should be handled with gloves and appropriate health and safety protection. The compound is also ] and exposure may produce severe eye damage or blindness.<ref name="MSDS">{{cite web | publisher = JT Baker| title = Potassium dichromate MSDS | url = http://www.jtbaker.com/msds/englishhtml/p5719.htm}}</ref> |
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As with other ] compounds, potassium dichromate is ]ic.<ref name="book100C">{{cite book |
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==Sulfur dioxide== |
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|author = IARC |
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Potassium dichromate paper can be used to test for ], as it turns distinctively from orange to green. This is typical of all redox reactions where hexavalent chromium is reduced to the less harmful trivalent chromium. Therefore, it is not a conclusive test for sulfur dioxide. |
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|author-link = International Agency for Research on Cancer |
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|title = Volume 100C: Arsenic, Metals, Fibres, and Dusts |
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|orig-year = 17-24 March 2009 |
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|url = https://publications.iarc.fr/_publications/media/download/3026/50ed50733f7d1152d91b30a803619022ef098d59.pdf |
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|access-date = 2020-01-05 |
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|date = 2012 |
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|isbn = 978-92-832-0135-9 |
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|quote = There is ''sufficient evidence'' in humans for the carcinogenicity of chromium (VI) compounds. Chromium (VI) compounds cause cancer of the lung. Also positive associations have been observed between exposure to Chromium (VI) compounds and cancer of the nose and nasal sinuses. There is ''sufficient evidence'' in experimental animals for the carcinogenicity of chromium (VI) compounds. Chromium (VI) compounds are ''carcinogenic to humans (Group 1)''. |
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|publisher = International Agency for Research on Cancer |
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|location = Lyon |
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}}</ref> The compound is also ] and exposure may produce severe eye damage or blindness.<ref name="MSDS">{{cite web | publisher = JT Baker| title = Potassium dichromate MSDS | url = http://hazard.com/msds/mf/baker/baker/files/p5719.htm}}</ref> Human exposure further encompasses impaired fertility. |
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==References== |
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==References== |
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{{Potassium compounds}} |
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{{Chromates and dichromates}} |
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{{DEFAULTSORT:Potassium Dichromate}} |
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