Conversion. Copper and brass processing. Analyzing the amount of copper and lead in the brasses. In this test the laboratory checks samples of brass from the mill's production to make sure they are the correct mixture. Samples are dissolved in acid and subsequently electrolyzed. The copper is plated out on the cathode negative electrode and the lead on the anode positive electrode. The percentages of each metal present are determined by weighing the electrodes before and after electrolyzing. Chase and Brass Company, Euclid, Ohio. Sourced from the Library of Congress.