chemistry

Murexide

Murexide 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 Murexide rather than just read about it. In short: Murexide (NH4C8H4N5O6, or C8H5N5O6·NH3), also called ammonium purpurate or MX, is the ammonium salt of purpuric acid. It is a purple solid that is soluble in water.

Key takeaways

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

Reference excerpt

Murexide (NH4C8H4N5O6, or C8H5N5O6·NH3), also called ammonium purpurate or MX, is the ammonium salt of purpuric acid. It is a purple solid that is soluble in water. The compound was once used as an indicator reagent. Aqueous solutions are yellow at low pH, reddish-purple in weakly acidic solutions, and blue-purple in alkaline solutions.

Preparation Murexide is prepared by treating alloxantin with ammonia to 100 °C, or by treating uramil (5-aminobarbituric acid) with mercury oxide. It may also be prepared by digesting alloxan with alcoholic ammonia.

History Justus von Liebig and Friedrich Wöhler in Giessen, Germany, had investigated the purple product, murexide, obtained from snake excrement in the 1830s, but this was not an abundant raw material, and a method of using it as a dyestuff was not established at that time. In the 1850s, French colourists and dye-producers, such as Depoully in Paris, succeeded in making murexide from abundant South American guano and of applying it to natural fibres. It was then widely adopted in Britain, France and Germany.

Use Murexide is used in analytical chemistry as a complexometric indicator for complexometric titrations, most often of calcium ions, but also for copper, nickel, cobalt, thorium and rare-earth metals. It functions as a tridentate ligand. Its use has been eclipsed by calcium-ion selective electrodes.

References

This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Murexide". Encyclopædia Britannica. Vol. 19 (11th ed.). Cambridge University Press. p. 36.

Illustrations

Worked examples

Example 1 — a first encounter with Murexide

Start with the simplest possible case. Write down what Murexide 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 Murexide 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 Murexide 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 Murexide

In research: Murexide 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 Murexide 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: Murexide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ammonium compounds, Complexometric indicators, Dyes, so understanding it makes those chapters shorter.
In everyday life: Look for Murexide 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 Murexide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Murexide 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 Murexide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Murexide in simple terms?

Murexide (NH4C8H4N5O6, or C8H5N5O6·NH3), also called ammonium purpurate or MX, is the ammonium salt of purpuric acid. It is a purple solid that is soluble in water.

Why does Murexide 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 Murexide?

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 Murexide.