Question

Silver containing lead as an impurity is removed by (a) distillation (b) poling (c) levigation (d) cupellation

Short answer

(d) cupellation

Step-by-step solution

Understanding the Terminology

First, understand the terms used in the options. Distillation is a process of separating substances based on differences in boiling points. Poling is a refining method for certain metals which involves stirring with green wood to remove impurities. Levigation involves grinding an ore to a fine powder and washing with water to separate impurities. Cupellation is a refining process used to separate noble metals like silver and gold from base metals like lead by heating them in a special furnace.

Identify the Applicable Method for Silver

Consider which of the named processes is commonly used to refine silver from impurities such as lead. Cupellation is specifically known for refining precious metals such as silver and gold by separating them from lead and other impurities. This makes cupellation the appropriate method for refining silver by removing lead as an impurity.

Review and Confirm Your Answer

After understanding the definitions and applications of each method, confirm that cupellation is the correct answer. Silver refining traditionally uses cupellation because it allows for the removal of lead impurities by oxidation and absorption into the cupel, leaving behind pure silver.

Key concepts

Silver Refining

Silver refining is an essential process to get pure, usable silver from raw ores that often contain impurities. In refining, these unwanted materials are separated and removed to improve the quality of the silver. There are various methods available, but each targets specific refining needs.
When refining silver, one often encounters impurities like lead, which requires specific techniques to purify the silver effectively. The refined silver produced from this process is used in a variety of applications, including jewelry, electronics, and photographic equipment. Understanding the correct refining process is crucial for anyone working with raw silver ores to ensure maximum purity and quality.

Lead Impurities

Lead is a common impurity found within silver ores. Its removal is crucial because even small amounts of lead can significantly diminish the value and quality of the silver. Additionally, lead poses environmental and health risks.
The presence of lead in silver ores necessitates careful processing techniques to ensure that the final product is free of contaminants. It's important to select a method that effectively removes lead while maintaining the integrity of the silver. Cupellation is one such method that has been proven effective over centuries.

• Lead affects the appearance and durability of silver.
• Handling lead requires safety considerations due to its toxicity.
• Efficient removal ensures that the refined silver is of high market value.

Separation Processes

Separation processes in metallurgy are critical for isolating desired metals from their ores. These processes take advantage of differences in physical or chemical properties of the materials.
One of the key separation processes for silver refining is cupellation, where silver is separated from lead and other impurities by heating. This method leverages the high melting point of silver compared to the impurities.

• This process involves high temperatures to ensure effective separation.
• Separation processes must be chosen based on the specific impurities present in the ore.
• Accurate separation enhances the quality of the final metal product.

Noble Metals Extraction

Noble metals like silver and gold are highly valued due to their stability, conductivity, and rarity. They are called "noble" because they resist corrosion and oxidation even at high temperatures. Extracting these elements from ores involves processes designed to separate them from less desirable metals such as lead.
Cupellation is a well-known and ancient technique used in the extraction of noble metals. This process utilizes the melting point differences and chemical properties to isolate precious metals effectively.

• Noble metals are resistant to corrosion, making their extraction valuable for many industries.
• Extraction processes, like cupellation, must efficiently remove base metal impurities.
• The purity achieved through these processes determines the commercial value of the metals.