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| ImageFile = Cobalt(II)-thiocyanate-trihydrate-xtal-1976-CM-3D-balls.png |
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| ImageFile = Hg(SCN)2 Xray.jpg |
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| ImageFile1 = Powder_sample_of_Co(NCS)2.png |
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| Section1 = {{Chembox Identifiers |
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|Section1={{Chembox Identifiers |
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| CASNo_Ref = {{cascite|correct|??}} |
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| CASNo = 3017-60-5 |
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| EINECS = 221-156-8 |
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| CASNo = 3017-60-5 |
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| CASNo1 = 61497-93-6 |
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| CASNo1_Comment = (trihydrate) |
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| Section2 = {{Chembox Properties |
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| UNII = Q59BVN759I |
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| Co = 1 | S = 2 | C = 2 | N = 2 |
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| EINECS = 221-156-8 |
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| PubChem = 18174 |
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| SMILES = C(#N).C(#N). |
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| InChI = 1/2CHNS.Co/c2*2-1-3;/h2*3H;/q;;+2/p-2 |
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| StdInChI = 1S/2CHNS.Co/c2*2-1-3;/h2*3H;/q;;+2/p-2 |
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| Co=1 | S=2 | C=2 | N=2 |
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| MolarMass = 175.098 g/mol |
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| Density = 2.484 g/cm<sup>3</sup> |
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| MagSus = +11,090·10<sup>−6</sup> cm<sup>3</sup>/mol }} |
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'''Cobalt(II) thiocyanate''' is an ] with the formula Co(SCN)<sub>2</sub>.<ref name=":0">{{Cite journal|last1=Shurdha|first1=Endrit|last2=Lapidus|first2=Saul H.|last3=Stephens|first3=Peter W.|last4=Moore|first4=Curtis E.|last5=Rheingold|first5=Arnold L.|last6=Miller|first6=Joel S.|date=2012-09-17|title=Extended Network Thiocyanate- and Tetracyanoethanide-Based First-Row Transition Metal Complexes|journal=Inorganic Chemistry|language=en|volume=51|issue=18|pages=9655–9665|doi=10.1021/ic300804y|pmid=22928927|issn=0020-1669}}</ref> The anhydrous compound is a ] with a layered structure. The ], Co(SCN)<sub>2</sub>(H<sub>2</sub>O)<sub>3</sub>, is a ] used in the '''cobalt thiocyanate test''' (or '''Scott test''') for detecting ]. The test has been responsible for widespread false positives and false convictions.<ref name="Propublica-1">{{cite web |url=https://www.propublica.org/article/common-roadside-drug-test-routinely-produces-false-positives |
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'''Cobalt(II) thiocyanate''' is an ] of ]. It is best known for the '''cobalt thiocyanate test''' (or '''Scott test'''), which is a proven screening test for the presence of ]. |
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|title=Busted: Tens of thousands of people every year are sent to jail based on the results of a $2 roadside drug test. Widespread evidence shows that these tests routinely produce false positives. Why are police departments and prosecutors still using them? |author=Ryan Gabrielson |author2=Topher Sanders |website=ProPublica |date= July 7, 2016}}</ref><ref name="Propublica-2">{{cite web |url=https://www.propublica.org/article/no-field-test-is-fail-safe-meet-the-chemist-behind-houston-police-drug-kits |title= 'No Field Test is Fail Safe': Meet the Chemist Behind Houston's Police Drug Kits |author=Ryan Gabrielson |website=ProPublica |date= July 11, 2016}}</ref> |
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==Structure and preparation== |
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==Preparation== |
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] |
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This compound may be prepared by the ] reaction of aqueous ] and ]; ] precipitates, leaving the desired compound in solution:<ref>{{cite journal | last1 = Cano | first1 = F. H. | last2 = García-Blanco | first2 = S. | last3 = Laverat | first3 = A. G. | title = The crystal structure of cobalt(II) thiocyanate trihydrate | journal = Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry | volume = 32 | pages = 1526 | year = 1976 | doi = 10.1107/S0567740876005694 | issue = 5}}</ref> |
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The structures of Co(SCN)<sub>2</sub> and its hydrate Co(SCN)<sub>2</sub>(H<sub>2</sub>O)<sub>3</sub> have been determined using ].<ref name=":0" /> Co(SCN)<sub>2</sub> forms infinite 2D sheets in the ] structure type, where as Co(SCN)<sub>2</sub>(H<sub>2</sub>O)<sub>3</sub> consists of isolated tetrahedral Co(SCN)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub> centers and one equivalent of ].<ref name=Xray/> |
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The hydrate may be prepared by the ] reactions, such as the reaction of aqueous ] and ] to produce a ] precipitate, leaving the hydrate of Co(SCN)<sub>2</sub> in solution:<ref name=Xray>{{cite journal | last1 = Cano | first1 = F. H. | last2 = García-Blanco | first2 = S. | last3 = Laverat | first3 = A. G. | title = The crystal structure of cobalt(II) thiocyanate trihydrate | journal = Acta Crystallographica Section B | volume = 32 | pages = 1526 | year = 1976 | doi = 10.1107/S0567740876005694 | issue = 5}}</ref> |
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:CoSO<sub>4</sub> (aq) + Ba(SCN)<sub>2</sub> (aq) → BaSO<sub>4</sub> (s) + Co(SCN)<sub>2</sub> (aq) |
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:CoSO<sub>4</sub> + Ba(SCN)<sub>2</sub> → BaSO<sub>4</sub> + Co(SCN)<sub>2</sub> |
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==Cobalt thiocyanate test== |
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or the reaction of the hexakisacetonitrile cobalt(II) tetrafluoroborate and ], precipitating KBF<sub>4</sub> |
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The cobalt thiocyanate reagent can be prepared by dissolving ten ] of cobalt (II) thiocyanate in a mixture of 490 ] of distilled water and 500 milliliters of ].{{Citation needed|date=August 2010}} |
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:(BF<sub>4</sub>)<sub>2</sub> + 2KSCN → 2KBF<sub>4</sub> + Co(SCN)<sub>2</sub>. |
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The cobalt thiocyanate test is performed by placing approximately 2 to 4 milligrams of a target substance in a glass test tube, then 5 drops of cobalt thiocyanate reagent. After shaking, 1 or 2 drops of concentrated ] (other acids can be used<ref>{{cite journal | journal = ] | url = http://www.justice.gov/dea/programs/forensicsci/microgram/journal_v1/mjournal_v1_pg6a.html | title = A Study of Acids Used for the Acidified Cobalt Thiocyanate Test for Cocaine Base | |
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author = Anna L. Deakin | volume = 1 | pages = 40–43 | year = 2003}}</ref> are added, and the tube is again shaken. Ten drops of ] (or similar solvent)) are then added, and the tube is ], then allowed to settle and separate into two layers. The final color of the chloroform (organic) layer is recorded. |
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The anhydrate can then be prepared via addition of ] as an antisolvent.<ref name=":0" /> |
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Addition of the cobalt thiocyanate reagent to cocaine hydrochloride results in the surface of the particles turning a bright blue (faint blue for cocaine base). The solution changes back to pink upon adding one or two drops of hydrochloric acid and mixing. Addition of 10 drops of chloroform, vortexing, and allowing the solution to settle results in a blue organic layer for both cocaine hydrochloride and cocaine base. |
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==Cobalt thiocyanate test== |
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] and ] also give blue organic layers. These compounds are known false positives for cocaine. |
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Detailed procedures for the cobalt thiocyanate test, often sold as the "morris reagent" are available. The reagent consists of 2% cobalt thiocyanate dissolved in dilute acid.<ref>{{cite journal |last=Deakin |first=Anna |date=2003 |title=A Study of Acids Used for the Acidified Cobalt Thiocyanate Test for Cocaine Base |url=http://forendex.safs1966.org/uploads/references/MicrogramJournal/1.1-2.40.43.pdf |journal=Microgram Journal |volume=1 |issue=1–2 |pages=40–43 |archive-url=https://web.archive.org/web/20190316143130/http://forendex.safs1966.org/uploads/references/MicrogramJournal/1.1-2.40.43.pdf |archive-date=16 March 2019}}</ref> Glycerol is often added to stabilise the cobalt complex, ensuring it only goes blue when in contact with an analyte and not due to drying.<ref>{{Cite journal |last1=Haddoub |first1=Rose |last2=Ferry |first2=Daniel |last3=Marsal |first3=Philippe |last4=Siri |first4=Olivier |date=2011 |title=Cobalt thiocyanate reagent revisited for cocaine identification on TLC |url=http://xlink.rsc.org/?DOI=c1nj20234k |journal=New Journal of Chemistry |language=en |volume=35 |issue=7 |pages=1351 |doi=10.1039/c1nj20234k |issn=1144-0546}}</ref> |
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Addition of the cobalt thiocyanate reagent to cocaine hydrochloride results in the surface of the particles turning a bright blue (faint blue for cocaine base). The solution changes back to pink upon adding some hydrochloric acid. Addition of chloroform, results in a blue organic layer for both cocaine hydrochloride and cocaine base. ] and ] also give blue organic layers. These compounds are known false positives for cocaine. Lidocaine is commonly used to adulterate or mimic cocaine due to its local anaesthetic effect. |
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If the procedure is adjusted to basify the sample rather than acidifying it, the test can be used to test for ketamine hydrochloride.<ref name='modified CoSCN'>{{cite journal | title = Modified Cobalt Thiocyanate Presumptive Color Test for Ketamine Hydrochloride | journal = J Forensic Sci | date = 2007 | first = JA | last = Morris | volume = 52 | issue = 1 | pages = 84–87| pmid=17209915 | doi=10.1111/j.1556-4029.2006.00331.x| s2cid = 27411302 }}</ref> |
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==References== |
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==References== |
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{{cobalt compounds}} |
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{{sulfur compounds}} |
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