The document describes the preparation of reagents for the limit test for arsenic. It involves preparing a test solution using water and stanneted hydrochloric acid from the water soluble substance being tested. For insoluble substances, the solution is obtained using brominated hydrochloric acid. Stannated hydrochloric acid is prepared by adding 1 ml of stannous chloride solution to 100 ml of hydrochloric acid and serves as a reagent. The test is then repeated using a standard arsenic solution to produce a faint yellow stain.