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.
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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