Aqua Regia Recipes For Testing Gold

Aqua Regia

Aqua regia or aqua regis (Latin for royal water or king's water) is a highly corrosive, fuming yellow or red solution, also called nitro-hydrochloric acid. The mixture is formed by freshly mixing concentrated nitric acid and concentrated hydrochloric acid, usually in a volumetric ratio of 1:3 respectively, although other ratios are made and used to test varying purities of gold. It was named so because it can dissolve the so-called "royal metals," or noble metals, gold and platinum.

Aqua Regia is one of only a few solvents that will dissolve gold.

One can also use aqua regia to test high karat gold to determine purity or fineness.

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These acids are very corrosive and very dangerous!

They will burn your skin and ANY thing else they come in contact with!

The fumes are toxic and hazardous, they will burn skin too!

Mixtures containing both nitric and hydrochloric acids off-gas chlorine gas and may explode if their container is sealed. Never seal a container of aqua regia. Always leave the cap loose to let the gas escape!

These recipes of Aqua Regia will last approximately 3-4 weeks before they lose potency.

Aqua Regia Recipes

Use these recipes to make testing solutions to test copper, brass, bronze, lead, tin, zinc, silver plate, gold plate, solid silver, sterling silver, all solid karat gold items, platinum and palladium.

Use them to determine whether or not an item is plated or solid and also to determine purity.

These acids react differently with different elements.

• Copper, brass, and bronze will fizz violently and turn green with a strong odor and brown smoke.

• Lead and zinc will foam, fizz a little and turn black.

• Tin will bubble lightly and turn yellowish.

• Place acid in a filed notch to determine if there is copper underneath plated silver or gold.

• Low purity silver, 50-65% Ag, may turn green due to the high levels of copper alloyed in it.

• Solid sterling and pure silver will turn a cloudy cream color.

• Low purity solid gold, 8k-9k, may turn slightly darker, or the color of tea, but otherwise should not react at all. All of these acids will sit like a drop of water on 10k-24k. However, aqua regia will dissolve pure gold.

• Platinum and palladium require full strength aqua regia. The reactions may take up to 15-20 minutes and may be accelerated by applying heat.

To Test For: Acids Ratio Chemical
Gold Plate Nitric, Water 3:1 HNO3
Silver Plate Nitric, Water 3:1 HNO3
500-999 Silver Nitric, Water 3:1 HNO3
8k-14k Karat Gold, Tin, Lead, Zinc Nitric 1:1 HNO3
10k-18k Karat Gold Aqua Regia Hydrochloric, Nitric, Water 1:50:12 respectively* 1HCl+50HNO3+12H2O
14k-22k Karat Gold Aqua Regia Hydrochloric, Nitric 3:1 3HCl+1HNO3
18k-24k Karat Gold Aqua Regia Hydrochloric, Nitric 4:1 4HCl+1HNO3
20k-24k Karat Gold, Platinum, Palladium Aqua Regia Hydrochloric, Nitric 41:9** 41HCl+9HNO3

* ALWAYS add acid to water! NEVER add water to acid!

** True Aqua Regia