The purest gold obtainable is required for use as standards or check pieces in the assay of gold bullion. The following method of preparing it is now in use at the Mint. Gold assay cornets from the purest gold which can be obtained are dissolved in nitrohydrochloric acid, and the excess of nitric acid expelled … Read more
It is often impracticable to apply the ordinary parting assay to the examination of low-standard alloys of gold with other metals. These are then tested by various other methods, of which a summary is given below, the alloys being grouped in four series for convenience: A. Alloys requiring scorification. B. Amalgams. C. Alloys containing members … Read more
The Gold Fire Assay Process of ores is almost universally conducted in the dry procedure by furnace methods. Exceptions will be noted later. The plan of operation is to concentrate the precious metal in a button of lead either (1) Fire Assay By fusion in a crucible; or, more rarely, (2) Fire Assay By scorification. … Read more
The following remarks on the use of the fire assay fluxes and litharge may serve as an aid in arriving to a correct composition of charges for most cases: Litharge or red lead is added in the proportion of one or two parts to two of ore; if too much litharge (lead oxide) is used the … Read more
The bead of silver and gold obtained by cupellation is squeezed between pliers, or flattened by a hammer on a clean anvil, to loosen the bone ash adhering to its lower surface, and is then cleaned by a brush of wires or stiff bristles. It is then weighed, the silver removed by solution in nitric … Read more
Cupellation is conducted in a muffle furnace, the construction of which is shown in Figs. 62-63. The fire is lighted, a little bone-ash is sprinkled on the floor of the muffle to prevent its corrosion by litharge in case of the upsetting of a cupel, and the cupels introduced as soon as a bright red … Read more
“Highgrading” a polite word for stealing gold and silver for your refinery, has been a way of life since the metals in native form have been mined or produced. Unfortunately, in the past, highgraders were not always severely prosecuted or even looked upon unfavorably in their communities. Recent high metal prices with attendant world wide … Read more
This keeps the leach sample secure prior to its assaying. A simple electric box, lock and key, piece of pipe, funnel, bottle and yes, some wire.
It is often desirable to ascertain by preliminary experiments the quantity of alkali which will be needed to neutralize acidity in any particular ore. In this connection a distinction is sometimes made between “ free ” and “ latent ” acidity. The free acidity is that due to substances soluble in water, and is determined … Read more
Organic carbon is a common problem for base metal production and precious metal leaching. In froth flotation, liberated organic carbon is naturally hydrophobic and will be recovered with the other minerals, lowering the grade of the concentrates. It can also adsorb collectors and frothers, reducing the efficiency of the mineral recovery process. In leaching, the … Read more