When refining gold, it is essential that the precipitated pure gold is thoroughly rinsed to wash away any clinging dissolved impurities, such as copper chloride. This test liquid is used to detect dissolved impurities by changing color. Ammonia Test Liquid is reagent grade (chemically pure) ammonia and highly concentrated (100 times more concentrated than household ammonia). It is easy to use and comes with both complete instructions as well as a link to free and complete instructions for the entire gold refining process. One bottle is typically sufficient for a full year of tests.