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mathematics

Gold number

Gold number is a mathematics 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 Gold number rather than just read about it. In short: The gold number is the minimum weight (in milligrams) of a protective colloid/lyophilic colloid required to prevent the coagulation of 10 ml of a standard hydro gold sol when 1 ml of a 10% sodium chloride solution is added to it. It was first used by Richard Adolf Zsigmondy in 1901.

Key takeaways

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

Reference excerpt

The gold number is the minimum weight (in milligrams) of a protective colloid/lyophilic colloid required to prevent the coagulation of 10 ml of a standard hydro gold sol when 1 ml of a 10% sodium chloride solution is added to it. It was first used by Richard Adolf Zsigmondy in 1901. An electrical double layer is normally present on the gold sol particles, resulting in electrostatic repulsion between the particles. The sodium chloride ions disrupt this electrical double layer, causing coagulation to occur. The coagulation of gold sol results in an increase in particle size, indicated by a colour change from red to blue or purple. The higher the gold number, the lower the protective power of the colloid, because a greater amount of colloid is required to prevent coagulation. The gold number of some colloids are given below.

References

Worked examples

Example 1 — a first encounter with Gold number

Start with the simplest possible case. Write down what Gold number claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, 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 Gold number 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 Gold number 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 Gold number

In research
Gold number appears in mathematics 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 Gold number 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
Gold number is common in secondary-school and first-year university syllabi. It links to neighbouring topics Colloidal chemistry, so understanding it makes those chapters shorter.
In everyday life
Look for Gold number 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 Gold number in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Gold number means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Gold number out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gold number in simple terms?

The gold number is the minimum weight (in milligrams) of a protective colloid/lyophilic colloid required to prevent the coagulation of 10 ml of a standard hydro gold sol when 1 ml of a 10% sodium chloride solution is added to it. It was first used by Richard Adolf Zsigmondy in 1901.

Why does Gold number matter?

Because it connects several mathematics 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 Gold number?

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 Gold number.

Tags

  • Colloidal chemistry

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