Discarding gold solution that has been tested "no gold" by old and used up test solution can be very costly. 6. Bibliography. Refining Precious Metal Wastes by C.M. Hoke. Metallurgical Publishing Co., 123 William Street, New York, U.S.A. 1940. University Microfilms International, 300 N. Zeeb Road, Ann Arbor, Michigan 48106, U.S.A. and 18 Bedford Row, London WC1R 4EJ, England.