Chloroauric acid - HAuCl4·3H2O
Chloroauric acid, sometimes erroneously called "gold chloride", is an extremely deliquescent solid, which cannot be kept in the solid state, when in contact with air. For this reason it usually is sold in glass ampoules, which are hermetically sealed and need to be broken up, just before use of the compound.
This sample is 1 gram of this solid, 99.9% purity. Almost exactly 50% of its weight is due to gold, 1 gram of chloroauric acid can be reduced to obtain 0.5 gram of gold.
The solid is orange/yellow, the solutions are purely deep yellow. The picture below shows a solution of 4% solution in water. In this way, chloroauric acid also frequently is sold, as solutions with concentrations ranging from 1% to 10%, the gold contents then being 0.5% to 5%.