Cobalt(II) thiocyanate is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula Co(SCN)₂. The anhydrous compound is a

coordination polymer Coordination may refer to: * Coordination (linguistics), a compound grammatical construction * Coordination complex, consisting of a central atom or ion and a surrounding array of bound molecules or ions ** A chemical reaction to form a coordinat ...

with a layered structure. The

trihydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

, Co(SCN)₂(H₂O)₃, is a isothiocyanate complex used in the cobalt thiocyanate test (or Scott test) for detecting

cocaine Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...

Structure and preparation

left, 259x259px, Structure of Co(SCN)₂. The structures of Co(SCN)₂ and its hydrate Co(SCN)₂(H₂O)₃ have been determined using

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

. Co(SCN)₂ forms infinite 2D sheets as in the

mercury(II) thiocyanate Mercury(II) thiocyanate () is an inorganic chemical compound, the coordination complex of and the thiocyanate anion. It is a white powder. It will produce a large, winding "snake" when ignited, an effect known as the Pharaoh's serpent. Synthes ...

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 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 hydrate may be prepared by the

salt metathesis A salt metathesis reaction (also called a double displacement reaction, double replacement reaction, or double decomposition) is a type of chemical reaction in which two ionic compounds in aqueous solution exchange their component ions to form two ...

reactions, such as the reaction of aqueous

cobalt(II) sulfate 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 m ...

and

barium thiocyanate Barium thiocyanate refers to salts of the formula . Both an anhydrous salt and a trihydrate are known. The anhydrous salt is hygroscopic. The trihydrate is soluble in most alcohols but insoluble in simple alkanes. Barium thiocyanate is used in dy ...

to produce a

barium sulfate Barium sulfate (or sulphate) is the inorganic compound with the chemical formula Ba SO4. It is a white crystalline solid that is odorless and insoluble in water. It occurs in nature as the mineral barite, which is the main commercial source of ...

precipitate, leaving the hydrate of Co(SCN)₂ in solution: :CoSO₄ + Ba(SCN)₂ → BaSO₄ + Co(SCN)₂ or the reaction of the hexakisacetonitrile cobalt(II) tetrafluoroborate and

potassium thiocyanate Potassium thiocyanate is the chemical compound with the molecular formula KSCN. It is an important salt of the thiocyanate anion, one of the pseudohalides. The compound has a low melting point relative to most other inorganic salts. Uses Ch ...

, precipitating KBF₄ : o(NCMe)₆BF₄)₂ + 2KSCN → 2KBF₄ + Co(SCN)₂. The anhydrate can then be prepared via addition of

diethylether Diethyl ether, or simply ether, is an organic compound with the chemical formula , sometimes abbreviated as . It is a colourless, highly Volatility (chemistry), volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs ...

as an antisolvent.

Scott's test

Scott's Test or Scott Test refers to a rapid and low-cost method of preliminary testing for

. It is a mixture of an acid medium and 2% cobalt(II) thiocyanate. While typically used for cocaine, it will also indicate the presence of ketamine hydrochlorides,

heroin Heroin, also known as diacetylmorphine and diamorphine among other names, is a morphinan opioid substance synthesized from the Opium, dried latex of the Papaver somniferum, opium poppy; it is mainly used as a recreational drug for its eupho ...

, and

dibucaine Cinchocaine (INN/ BAN) or dibucaine ( USAN) is an amide local anesthetic. Among the most potent and toxic of the long-acting local anesthetics, current use of cinchocaine is generally restricted to spinal and topical anesthesia. It is sold under t ...

in amounts higher than 1 mg, as well as

diltiazem Diltiazem, sold under the brand name Cardizem among others, is a nondihydropyridine calcium channel blocker medication used to treat high blood pressure, angina, and certain heart arrhythmias. It may also be used in hyperthyroidism if beta b ...

and

lidocaine Lidocaine, also known as lignocaine and sold under the brand name Xylocaine among others, is a local anesthetic of the amino amide type. It is also used to treat ventricular tachycardia and ventricular fibrillation. When used for local anae ...

in amounts higher than or equal to 5 mg. When the cobalt thiocyanate reagent interacts with cocaine hydrochloride, the solution turns from a reddish-brown to a vibrant blue. The test has been responsible for widespread false positives and false convictions.

Cobalt thiocyanate test

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. 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. 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 Diphenhydramine, sold under the brand name Benadryl among others, is an antihistamine and sedative. Although generally considered sedating, diphenhydramine can cause paradoxical central nervous system stimulation in some individuals, particula ...

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

References

{{sulfur compounds Thiocyanates Cobalt(II) compounds Chemical tests Drug testing reagents Cocaine