chemistry

Wolffram's red salt

Wolffram's red salt 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 Wolffram's red salt rather than just read about it. In short: Wolffram’s Red Salt is an inorganic compound with the formula [Pt(C2H5NH2)4Cl2][Pt(C2H5NH2)4]Cl4·4H2O. This compound is an early example of a one-dimensional coordination polymer, serving as a representative structure for studies in solid-state physics.

Key takeaways

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

Reference excerpt

Wolffram’s Red Salt is an inorganic compound with the formula [Pt(C2H5NH2)4Cl2][Pt(C2H5NH2)4]Cl4·4H2O. This compound is an early example of a one-dimensional coordination polymer, serving as a representative structure for studies in solid-state physics. This species has been of interest due to the unusual mixed valence system of Pt(II) and Pt(IV) bridged by a chlorine atom. The deep red color of the double salt, where the components were colorless, piqued the interest of early inorganic chemists and ultimately inspired studies into the physical properties of the compound in search of potential applications.

History In 1850, Charles-Adolphe Wurtz described a colorless platinum tetrammine with the formula [Pt(etn)4]Cl2 2H2O; Wolffram (H. Wolffram, Dissertation, Königsberg, 1900.), whom the compound is named after, obtained a red salt from this by action of hydrogen peroxide in hydrochloric acid, and initially considered it to be isomeric with Wurtz’s salt. With no known case of plato-tetrammine isomerism at the time, this prompted extensive discussion in the literature of the true nature and properties of Wolffram’s Red Salt.

Preparation Reihlen and Flohr demonstrated that Wolffram’s salt could be prepared directly by mixing aqueous solutions of the colorless [Pt(etn)4]Cl2 and its yellow analogue, [Pt(etn)4Cl2]Cl2, where etn = NH2CH2CH3, leading to the most probable conclusion of the double salt formula, [Pt(C2H5NH2)4Cl2][Pt(C2H5NH2)4]Cl4·4H2O, compared with concurrently postulated explanations of tervalent platinum.

Studies Early explanations for the deep red color of the salt were attributed to the special structure of the crystal lattice, albeit with little explanation. While Drew & Tess attempted to explain the deep color of this compound based on the assumption of a Pt(III) species, Jensen established the diamagnetism of the compound and proved that it did not involve Pt(III). Spectrochemical studies on the compound crystals concluded that the deep color of Wolffram’s salt crystals is due to the stacking of the “infinite chains” - linear Pt(II)/Pt(IV) stacked on top of each other. In 1960, the crystal structure was shown to be consistent with the formulated double salt, inspiring examinations of other analogues to compare and better understand this unique coordination pattern. Solid-state physical examinations were conducted to further elucidate the charge transfer across the mixed valence chain and potentially find use as semiconductors. X-ray scattering studies were performed, explicitly showing the mixed valence chain structure. Optical properties were probed, as well as potential use as a photocatalyst, albeit with disappointing results.

References

Illustrations

Worked examples

Example 1 — a first encounter with Wolffram's red salt

Start with the simplest possible case. Write down what Wolffram's red salt 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 Wolffram's red salt 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 Wolffram's red salt 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 Wolffram's red salt

In research: Wolffram's red salt 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 Wolffram's red salt 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: Wolffram's red salt is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chlorides, Chloro complexes, Inorganic compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Wolffram's red salt 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Wolffram's red salt” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Wolffram's red salt in 20 minutes

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

Frequently asked questions

What is Wolffram's red salt in simple terms?

Why does Wolffram's red salt 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 Wolffram's red salt?

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 Wolffram's red salt.