The effects of the presence of copper in a gold-silver alloy and of cleaning prior to analysis on the determination of the concentration of gold in coins by the specific gravity method have been investigated. It is shown that the presence of 5% of copper in a gold-silver alloy results in a measured gold content which is low by 3.3%. The average error introduced by not washing coins before measuring the specific gravity ranges between a 2.5% lowering of the measured gold content for very debased coins and a 1% lowering for those made of relatively pure gold.