science

Merrill–Crowe process

Merrill–Crowe process is a science 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 Merrill–Crowe process rather than just read about it. In short: The Merrill–Crowe Process is a separation technique for removing gold from the solution obtained by the cyanide leaching of gold ores. It is an improvement of the MacArthur-Forrest process, where an additional vacuum is managed to remove air in the solution (invention of Crowe), and zinc dust is used instead of zinc shavings (improvement of Merrill).

Key takeaways

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

Reference excerpt

The Merrill–Crowe Process is a separation technique for removing gold from the solution obtained by the cyanide leaching of gold ores. It is an improvement of the MacArthur-Forrest process, where an additional vacuum is managed to remove air in the solution (invention of Crowe), and zinc dust is used instead of zinc shavings (improvement of Merrill). The solution is separated from the ore by methods such as filtration (e.g. vertical leaf type clarifier filters) and counter current decantation (CCD). Afterwards a very clear solution is achieved by using pre-coated filters applying diatomaceous earth. Oxygen is then removed by passing the solution through a vacuum de-aeration column. Zinc dust is added to the clarified, de-aerated solution which precipitates the gold; zinc having a higher affinity for the cyanide ion than gold. Other precious metals, silver, and base metals, like copper, will also precipitate, if present. Automated membrane filtration offers a cost savings alternative to CCD. Both applications are compared in detail by K. McGrew, 2016. The gold precipitate (mixed with zinc dust) is then filtered out of the solution, and the zinc dust and gold are mixed with sulfuric acid to dissolve the zinc. The solution is filtered, and the remaining solids are smelted to a gold dore bar. These bars are sent to a refinery to remove the copper and silver, the specific process used depending upon the impurities in the gold. The basic process was discovered and patented by Charles Washington Merrill around 1900, and later refined by Thomas Bennett Crowe, working for the Merrill Company.

See also Other gold cyanidation techniques: Carbon in pulp Electrowinning Filter press

References

Worked examples

Example 1 — a first encounter with Merrill–Crowe process

Start with the simplest possible case. Write down what Merrill–Crowe process claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Merrill–Crowe process 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 Merrill–Crowe process 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 Merrill–Crowe process

In research: Merrill–Crowe process appears in science 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 Merrill–Crowe process 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: Merrill–Crowe process is common in secondary-school and first-year university syllabi. It links to neighbouring topics Gold, Metallurgical processes, so understanding it makes those chapters shorter.
In everyday life: Look for Merrill–Crowe process 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 Merrill–Crowe process in 20 minutes

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

Frequently asked questions

What is Merrill–Crowe process in simple terms?

Why does Merrill–Crowe process matter?

Because it connects several science 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 Merrill–Crowe process?

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 Merrill–Crowe process.