Make Purple Gold

Colored gold alloys are seen in jewelry and gold is often added to glass to give it color (e.g., ruby glass), but this project is a little different. You'll be performing any of a number of chemical reactions to make a gold chloride solution turn purple.

What You Do

• Mix together a dilute gold chloride solution (0.01%) and a 1% Rochelle salt (potassium sodium tartrate) solution. It's best if you use distilled water to prepare your solutions, as contaminants in tap water may affect your results.
• Another option is to make "Purple of Cassius". This is a purple gold made by introducing tin to a very dilute gold solution. The author of the article posted at The Alchemy Website attempted to produce this color by reacting a dilute solution of gold chloride with stannous chloride. He obtained an amber solution, but not the desired purple coloration.
• Gold may be reduced using formaldehyde. Add some sodium bicarbonate to a gold chloride solution to make the solution alkaline before introducing a drop of formalin.
• Another recipe calls for add a few milliliters of gold chloride to boiling water and then adding some 1% tri-sodium citrate and boiling the solution until the desired color is produced. This colloidal solution is best kept in a shady location, as it is said to be photoreactive.
• In general, gold chloride solution is photoreactive, so you could soak a filter paper with the solution and expose it to sunlight to seek a color change.

Alchemy is an experimental venture, so if you're interested in making purple gold, get out there and try some projects. Keep good notes and if you see good (or otherwise interesting) results, post specific instructions for other inquisitive people to try

Gold Alloys

Color of Gold	Alloy Composition
Yellow Gold (22K)	Gold 91.67% Silver 5% Copper 2% Zinc 1.33%
Red Gold (18K)	Gold 75% Copper 25%
Rose Gold (18K)	Gold 75% Copper 22.25% Silver 2.75%
Pink Gold (18K)	Gold 75% Copper 20% Silver 5%
White Gold (18K)	Gold 75% Platinum or Palladium 25%
White Gold (18K)	Gold 75% Palladium 10% Nickel 10% Zinc 5%
Gray-White Gold (18K)	Gold 75% Iron 17% Copper 8%
Soft Green Gold (18K)	Gold 75% Silver 25%
Light Green Gold (18K)	Gold 75% Copper 23% Cadmium 2%
Green Gold (18K)	Gold 75% Silver 20% Copper 5%
Deep Green Gold (18K)	Gold 75% Silver 15% Copper 6% Cadmium 4%
Blue-White or Blue Gold (18K)	Gold 75% Iron 25%
Purple Gold	Gold 80% Aluminum 20%

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