assaying

assaying (əsā`yĭng, ăs`āyĭng), in metallurgy, process of determining the specific metallic content of an ore, alloy, or other substance, especially one containing precious metals. It consists, in some cases, of subjecting the substance to complete chemical analysis and, in others, of simply determining the quantity present of one or more of the metal constituents. An accurate assay depends first upon procuring a representative sample of the ore in question. Since distribution of the ore's components is not uniform, a common method employed in obtaining this sample is to procure several samples, crush and mix them together, and from the final mass take the sample to be assayed. Assays are said to be gravimetric when the weight of the metal is determined and volumetric when the analysis involves the volume of the metal in solution as compared to that in a standardized solution. A wet assay (one which involves the use of liquid reagents) is generally used in a determination of weight. In a dry assay the ore is fused and the metal is finally obtained in a pure state.

---

assaying

In chemical analysis, the process of determining proportions of metal, particularly precious metal, in ores and metallurgical products. The most important assaying technique grew largely out of the experiments of the ancient alchemists and goldsmiths. Precious metals tend to occur as scattered particles randomly distributed, so a large sample of ore is required. Such large samples (typically containing gold, silver, and lead) are still most economically assayed by this ancient method, which involves several steps of heating and cooling. More sophisticated recent methods, such as spectrochemical analysis, are not suited to assaying precious metal ores because the samples of the inhomogeneous ore that must be used are larger than the instruments can handle. See also parting.