A pair of scales for weighing ore and buttons of base metal. It should take 10 ounces in each pan, and show 1/20 of a grain.
A bullion scale to be kept strictly for the precious metals. Loaded with one gramme, it should show 1/20 of a milligramme.
ASSAY BALANCE FOR BULLION.
Weights. Avoirdupois; troy, metric and "assay." Assay weights save much calculation. The unit of the system is a weight of 29.166 grammes. Its derivation is as follows:
2000 lbs. : 1 A.T. :: 1 oz. Troy : 1 milligramme.
To use this system, weigh out one A.T. of the ore and whatever number of milligrammes of gold and silver the assay gives indicates an equal number of Troy ounces to the ton of 2000 lbs. Avoirdupois.
A muffle and a melting furnace, portable and of medium size, are handy, though furnaces may be built of ordinary brick, lined with fire brick, that would be better for permanent use.
The fuels may be coke, anthracite or bituminous coal, charcoal, oil or gas.
