There are a few chemicals that can be used to test for the presence of gold in water:

Detecting Gold in Water

Rhodamine B

• Rhodamine B reacts with gold ions to form a red-colored complex.
• Adding it to water will turn reddish-pink if gold is present.

Stannous Chloride

• Stannous chloride reduces gold ions to elemental gold, which appears as a purple precipitate.
• This test detects gold dissolved in water rather than solid particles.

Lead Acetate Paper

• Lead acetate paper turns grey-black when exposed to gold solutions.
• The gold causes lead acetate to decompose into lead sulfide.

Sodium Thiosulfate

• Aqueous sodium thiosulfate can dissolve finely divided gold.
• The gold-thiosulfate complex takes on a yellowish color indicating gold’s presence.

Atomic Absorption Spectroscopy

• AAS can detect very low concentrations of dissolved gold in water through optical absorption.
• It does not work well for solid gold particles.

In summary, chemicals like rhodamine B, stannous chloride, and lead acetate can identify gold ions or particles dissolved or suspended in water through color reactions or precipitates. AAS provides high sensitivity gold detection in solutions.