Chapter 21: Problem 6

What is purple of Cassius? Discuss the method of its preparation and its uses.

Short Answer

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Purple of Cassius is an inorganic pigment, composed of colloidal gold and tin(IV) hydroxide. It is prepared by reducing Chloroauric Acid solution with Silver Nitrate solution and Stannous Chloride solution, followed by boiling. It is used in staining porcelain and glass and in electronics.

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Introduction on purple of Cassius

Purple of Cassius is a pigment that's a blend of tiny colloidal particles of gold and stannic (tin) hydroxide. It's a purple-red color that is used primarily in ceramics, but can also be used in staining glass or crystal.

Method of Preparation

In order to prepare the Purple of Cassius, an aqueous solution of Silver Nitrate (\(AgNO_3\)) is used to reduce a Chloroauric Acid solution (\(HAuCl_4\)). Afterward, a Stannous Chloride (\(SnCl_2\)) solution is added to the formed Gold Sol. As the last step, the solution is boiled until it appears purple in color. Always remember to follow laboratory safety rules when handling chemicals.

Explanation of the Reaction

[Stannous Chloride]\([SnCl_2]\) reduces [Chloroauric Acid]\([HAuCl_4]\) to form a sol of gold first. Here, stannous chloride gets oxidized to stannic chloride. The reduction of [Chloroauric Acid]\([HAuCl_4]\) by [Stannous Chloride]\([SnCl_2]\) is a redox reaction. The gold Salt sol particles are then absorbed by the hydrous stannic oxide formed from the boiling of the solution. This composite of gold and stannic oxide gives the beverage-purple tint.

Uses of Purple of Cassius

Purple of Cassius is broadly applied in the porcelain industry for staining porcelain red. It can additionally be utilized for staining glass. Notwithstanding its use in porcelain and glass, it finds applications in electronics due to the quality of gold. Therefore, Purple of Cassius can be applied in multiple fields.

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What is purple of Cassius? Discuss the method of its preparation and its uses.

Short Answer

Step by step solution

Introduction on purple of Cassius

Method of Preparation

Explanation of the Reaction

Uses of Purple of Cassius

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