Cobalt(II) thiocyanate

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Cobalt(II) thiocyanate
Hg(SCN)2 Xray.jpg
Powder sample of Co(NCS)2.png
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.019.234 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 221-156-8
PubChem CID
UNII
  • InChI=1S/2CHNS.Co/c2*2-1-3;/h2*3H;/q;;+2/p-2 X mark.svgN
    Key: INDBQWVYFLTCFF-UHFFFAOYSA-L X mark.svgN
  • InChI=1/2CHNS.Co/c2*2-1-3;/h2*3H;/q;;+2/p-2
    Key: INDBQWVYFLTCFF-NUQVWONBAI
  • C(#N)[S-].C(#N)[S-].[Co+2]
Properties
C2CoN2S2
Molar mass 175.098 g/mol
Density 2.484 g/cm3
+11,090·10−6 cm3/mol
Hazards
GHS labelling:
GHS-pictogram-exclam.svg GHS-pictogram-pollu.svg
Warning
H302, H312, H332, H410
P261, P264, P270, P271, P273, P280, P301+P312, P302+P352, P304+P312, P304+P340, P312, P322, P330, P363, P391, P501
Safety data sheet (SDS) External MSDS
Related compounds
Other anions
Cobalt(II) cyanate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Cobalt(II) thiocyanate is an inorganic compound with the formula Co(SCN)2. [1] The anhydrous compound is a coordination polymer with a layered structure. The trihydrate, Co(SCN)2(H2O)3, is a isothiocyanate complex used in the cobalt thiocyanate test (or Scott test) for detecting cocaine. The test has been responsible for widespread false positives and false convictions. [2] [3]

Contents

Structure and preparation

Structure of Co(SCN)2(H2O)3. Cobalt(II)-thiocyanate-trihydrate-xtal-1976-CM-3D-balls.png
Structure of Co(SCN)2(H2O)3.

The structures of Co(SCN)2 and its hydrate Co(SCN)2(H2O)3 have been determined using X-ray crystallography. [1] Co(SCN)2 forms infinite 2D sheets in the mercury(II) thiocyanate structure type, where as Co(SCN)2(H2O)3 consists of isolated tetrahedral Co(SCN)2(H2O)2 centers and one equivalent of water of crystallization. [4]

The hydrate may be prepared by the salt metathesis reactions, such as the reaction of aqueous cobalt(II) sulfate and barium thiocyanate to produce a barium sulfate precipitate, leaving the hydrate of Co(SCN)2 in solution: [4]

CoSO4 + Ba(SCN)2 → BaSO4 + Co(SCN)2

or the reaction of the hexakisacetonitrile cobalt(II) tetrafluoroborate and potassium thiocyanate, precipitating KBF4

[Co(NCMe)6](BF4)2 + 2KSCN → 2KBF4 + Co(SCN)2.

The anhydrate can then be prepared via addition of diethylether as an antisolvent. [1]

Cobalt thiocyanate test

Detailed procedures for the cobalt thiocyanate test are available. The reagent consists of 2% cobalt thiocyanate dissolved in dilute acid. [5] 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. [6]

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. Diphenhydramine and lidocaine 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.

If the procedure is adjusted to basify the sample rather than acidifying it, the test can be used to test for ketamine hydrochloride. [7]

Related Research Articles

In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively charged sodium ions and negatively charged chloride ions.

<span class="mw-page-title-main">Iron(II) sulfate</span> Chemical compound

Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate denotes a range of salts with the formula Fe SO4·xH2O. These compounds exist most commonly as the heptahydrate (x = 7) but several values for x are known. The hydrated form is used medically to treat or prevent iron deficiency, and also for industrial applications. Known since ancient times as copperas and as green vitriol (vitriol is an archaic name for sulfate), the blue-green heptahydrate (hydrate with 7 molecules of water) is the most common form of this material. All the iron(II) sulfates dissolve in water to give the same aquo complex [Fe(H2O)6]2+, which has octahedral molecular geometry and is paramagnetic. The name copperas dates from times when the copper(II) sulfate was known as blue copperas, and perhaps in analogy, iron(II) and zinc sulfate were known respectively as green and white copperas.

<span class="mw-page-title-main">Copper(II) sulfate</span> Chemical compound

Copper(II) sulfate, also known as copper sulphate, is an inorganic compound with the chemical formula CuSO4. It forms hydrates CuSO4·nH2O, where n can range from 1 to 7. The pentahydrate (n = 5), a bright blue crystal, is the most commonly encountered hydrate of copper(II) sulfate. Older names for the pentahydrate include blue vitriol, bluestone, vitriol of copper, and Roman vitriol. It exothermically dissolves in water to give the aquo complex [Cu(H2O)6]2+, which has octahedral molecular geometry. The structure of the solid pentahydrate reveals a polymeric structure wherein copper is again octahedral but bound to four water ligands. The Cu(II)(H2O)4 centers are interconnected by sulfate anions to form chains. Anhydrous copper sulfate is a light grey powder.

<span class="mw-page-title-main">Zinc sulfate</span> Chemical compound

Zinc sulfate describes a family of inorganic compounds with the formula ZnSO4(H2O)x. All are colorless solids. The most common form includes water of crystallization as the heptahydrate, with the formula ZnSO4·7H2O. As early as the 16th century it was prepared on the large scale, and was historically known as "white vitriol" (the name was used, for example, in 1620s by the collective writing under the pseudonym of Basil Valentine). Zinc sulfate and its hydrates are colourless solids.

<span class="mw-page-title-main">Calcium sulfate</span> Laboratory and industrial chemical

Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum. It has many uses in industry. All forms are white solids that are poorly soluble in water. Calcium sulfate causes permanent hardness in water.

<span class="mw-page-title-main">Thiocyanate</span> Ion (S=C=N, charge –1)

Thiocyanates are salts containing the thiocyanate anion [SCN]. [SCN] is the conjugate base of thiocyanic acid. Common salts include the colourless salts potassium thiocyanate and sodium thiocyanate. Mercury(II) thiocyanate was formerly used in pyrotechnics.

<span class="mw-page-title-main">Barium chloride</span> Chemical compound

Barium chloride is an inorganic compound with the formula BaCl2. It is one of the most common water-soluble salts of barium. Like most other water-soluble barium salts, it is a white powder, highly toxic, and imparts a yellow-green coloration to a flame. It is also hygroscopic, converting to the dihydrate BaCl2·2H2O, which are colourless crystals with a bitter salty taste. It has limited use in the laboratory and industry.

Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find the elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, therefore materials in other forms may need to be brought to this state before using standard methods. The solution is then treated with various reagents to test for reactions characteristic of certain ions, which may cause color change, precipitation and other visible changes.

In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization is the total mass of water in a substance at a given temperature and is mostly present in a definite (stoichiometric) ratio. Classically, "water of crystallization" refers to water that is found in the crystalline framework of a metal complex or a salt, which is not directly bonded to the metal cation.

Uranium(IV) sulfate (U(SO4)2) is a water-soluble salt of uranium. It is a very toxic compound. Uranium sulfate minerals commonly are widespread around uranium bearing mine sites, where they usually form during the evaporation of acid sulfate-rich mine tailings which have been leached by oxygen-bearing waters. Uranium sulfate is a transitional compound in the production of uranium hexafluoride. It was also used to fuel aqueous homogeneous reactors.

A solubility chart is a chart describing whether the ionic compounds formed from different combinations of cations and anions dissolve in or precipitate from solution.

<span class="mw-page-title-main">Vanadyl sulfate</span> Chemical compound

Vanadyl(IV) sulfate describes a collection of inorganic compounds of vanadium with the formula, VOSO4(H2O)x where 0 ≤ x ≤ 6. The pentahydrate is common. This hygroscopic blue solid is one of the most common sources of vanadium in the laboratory, reflecting its high stability. It features the vanadyl ion, VO2+, which has been called the "most stable diatomic ion".

<span class="mw-page-title-main">Mercury(II) sulfate</span> Chemical compound

Mercury(II) sulfate, commonly called mercuric sulfate, is the chemical compound HgSO4. It is an odorless salt that forms white granules or crystalline powder. In water, it separates into an insoluble basic sulfate with a yellow color and sulfuric acid.

<span class="mw-page-title-main">Manganese(II) sulfate</span> Chemical compound

Manganese(II) sulfate usually refers to the inorganic compound with the formula MnSO4·H2O. This pale pink deliquescent solid is a commercially significant manganese(II) salt. Approximately 260,000 tonnes of manganese(II) sulfate were produced worldwide in 2005. It is the precursor to manganese metal and many other chemical compounds. Manganese-deficient soil is remediated with this salt.

<span class="mw-page-title-main">Copper benzoate</span> Chemical compound

Copper benzoate is the chemical compounds with the formula Cu(C6H5CO2)2(H2O)x. These coordination complexes are derived from the cupric ion and the conjugate base of benzoic acid. Many derivatives are known with diverse ancillary ligands. This compound has found some use as a source of blue light in fireworks.

<span class="mw-page-title-main">Cobalt(II) sulfate</span> Inorganic compound

Cobalt(II) sulfate is any of the inorganic compounds with the formula CoSO4(H2O)x. Usually cobalt sulfate refers to the hexa- or heptahydrates CoSO4.6H2O or CoSO4.7H2O, respectively. The heptahydrate is a red solid that is soluble in water and methanol. Since cobalt(II) has an odd number of electrons, its salts are paramagnetic.

<span class="mw-page-title-main">Chromium(II) sulfate</span> Chemical compound

Chromium(II) sulfate refers to inorganic compounds with the chemical formula CrSO4·n H2O. Several closely related hydrated salts are known. The pentahydrate is a blue solid that dissolves readily in water. Solutions of chromium(II) are easily oxidized by air to Cr(III) species. Solutions of Cr(II) are used as specialized reducing agents of value in organic synthesis.

Moorhouseite is a rare mineral with the formula CoSO4•6H2O, a naturally occurring cobalt(II) sulfate hexahydrate. It is the lower-hydrate-equivalent of bieberite (heptahydrate) and aplowite (hexahydrate). It is also hydrated equivalent of cobaltkieserite. It occurs together with moorhouseite within efflorescences found in the Magnet Cove Barium Corporation mine in Walton, Nova Scotia, Canada.

Iron(II) selenate (ferrous selenate) is an inorganic compound with the formula FeSeO4. It has anhydrous and several hydrate forms. The pentahydrate has the structure, [Fe(H2O)4]SeO4•H2O, isomorphous to the corresponding iron(II) sulfate. Heptahydrate is also known, in form of unstable green crystalline solid.

References

  1. 1 2 3 Shurdha, Endrit; Lapidus, Saul H.; Stephens, Peter W.; Moore, Curtis E.; Rheingold, Arnold L.; Miller, Joel S. (2012-09-17). "Extended Network Thiocyanate- and Tetracyanoethanide-Based First-Row Transition Metal Complexes". Inorganic Chemistry. 51 (18): 9655–9665. doi:10.1021/ic300804y. ISSN   0020-1669. PMID   22928927.
  2. Ryan Gabrielson; Topher Sanders (July 7, 2016). "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?". ProPublica.
  3. Ryan Gabrielson (July 11, 2016). "'No Field Test is Fail Safe': Meet the Chemist Behind Houston's Police Drug Kits". ProPublica.
  4. 1 2 Cano, F. H.; García-Blanco, S.; Laverat, A. G. (1976). "The crystal structure of cobalt(II) thiocyanate trihydrate". Acta Crystallographica Section B. 32 (5): 1526. doi:10.1107/S0567740876005694.
  5. Deakin, Anna (2003). "A Study of Acids Used for the Acidified Cobalt Thiocyanate Test for Cocaine Base" (PDF). Microgram Journal. 1 (1–2): 40–43. Archived from the original (PDF) on 16 March 2019.
  6. Haddoub, Rose; Ferry, Daniel; Marsal, Philippe; Siri, Olivier (2011). "Cobalt thiocyanate reagent revisited for cocaine identification on TLC". New Journal of Chemistry. 35 (7): 1351. doi:10.1039/c1nj20234k. ISSN   1144-0546.
  7. Morris, JA (2007). "Modified Cobalt Thiocyanate Presumptive Color Test for Ketamine Hydrochloride". J Forensic Sci. 52 (1): 84–87. doi:10.1111/j.1556-4029.2006.00331.x. PMID   17209915. S2CID   27411302.