chemistry

Cobalt(II) thiocyanate

Cobalt(II) thiocyanate is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Cobalt(II) thiocyanate rather than just read about it. In short: Cobalt(II) thiocyanate is an inorganic compound with the formula Co(SCN)2. The anhydrous compound is a coordination polymer with a layered structure.

Key takeaways

Cobalt(II) thiocyanate belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Cobalt(II) thiocyanate to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Cobalt(II) thiocyanate from memory before moving on to harder problems.

Reference excerpt

Cobalt(II) thiocyanate is an inorganic compound with the formula Co(SCN)2. 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.

Structure and preparation

The structures of Co(SCN)2 and its hydrate Co(SCN)2(H2O)3 have been determined using X-ray crystallography. Co(SCN)2 forms infinite 2D sheets as 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. 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:

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.

Scott's test Scott's Test or Scott Test refers to a rapid and low-cost method of preliminary testing for cocaine. 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, and dibucaine in amounts higher than 1 mg, as well as diltiazem and lidocaine 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 added when using the reagent for Thin-layer chromatography as it stabilises the cobalt complex, ensuring it only goes blue when in contact with an analyte and not due to drying on the plate. 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 with 0.1 N sodium hydroxide rather than acidifying it, the test can be used to test for ketamine hydrochloride.

References

Illustrations

Worked examples

Example 1 — a first encounter with Cobalt(II) thiocyanate

Start with the simplest possible case. Write down what Cobalt(II) thiocyanate claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Cobalt(II) thiocyanate before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Cobalt(II) thiocyanate ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Cobalt(II) thiocyanate

In research: Cobalt(II) thiocyanate appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Cobalt(II) thiocyanate in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Cobalt(II) thiocyanate is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chemical tests, Cobalt(II) compounds, Cocaine, so understanding it makes those chapters shorter.
In everyday life: Look for Cobalt(II) thiocyanate outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Cobalt(II) thiocyanate in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Cobalt(II) thiocyanate means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Cobalt(II) thiocyanate out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Cobalt(II) thiocyanate in simple terms?

Cobalt(II) thiocyanate is an inorganic compound with the formula Co(SCN)2. The anhydrous compound is a coordination polymer with a layered structure.

Why does Cobalt(II) thiocyanate matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Cobalt(II) thiocyanate?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Cobalt(II) thiocyanate.