Hi Chuck:
Is this for crucible fusions, or cupelling? Or both?
The chamber atmosphere in the crucible fusion step is not important. Since the reducer is provide by the carbon (or other reducer present in your sample), you do not need an oxidizing or reducing atmosphere. Therefore, some furnaces for the crucible fusion are gas fired with the crucibles in the gas combustion chamber. Or, electric furnaces work well for the crucible fusion also. It depends on fuel you have available, furnace cost- those types of practical issues.
For cupelling it is a different story. Since you need oxygen to convert the molten lead into lead oxide, you cannot cupel in the combustion chamber of a gas fired furnace. All of the oxygen is consumed by the gas combustion, and there is none left for the cupellation. Believe me, I have tried it. The lead will melt, but it will never oxidize and the cupellation process will never finish. You CAN cupel in a gas furnace if you have a muffle chamber. The muffle will isolate the cupels from the combustion gas and you can allow oxygen into the muffle independent of the combustion chamber. Or, you can cupel in and electric furnace.
Gas furnaces may have more BTU's, and will therefore heat up and change temperature faster (although this does not have to be the case). Electric furnaces can be significantly less expensive. Many larger laboratories will have gas fired furnaces for the crucible fusion, and Cress electric furnaces for cupellation. They have accurate electronic digital controls to accurately control the temperature, exhaust systems, and are relatively inexpensive. You can see some popular models and details here:
http://www.Lmine.com/go.mvc?id=cress_assay_furnaces
The Cress furnaces can also be used for the crucible fusion, but the coiled elements can be damaged by any slag that spits out of the crucible.
Is this for crucible fusions, or cupelling? Or both?
The chamber atmosphere in the crucible fusion step is not important. Since the reducer is provide by the carbon (or other reducer present in your sample), you do not need an oxidizing or reducing atmosphere. Therefore, some furnaces for the crucible fusion are gas fired with the crucibles in the gas combustion chamber. Or, electric furnaces work well for the crucible fusion also. It depends on fuel you have available, furnace cost- those types of practical issues.
For cupelling it is a different story. Since you need oxygen to convert the molten lead into lead oxide, you cannot cupel in the combustion chamber of a gas fired furnace. All of the oxygen is consumed by the gas combustion, and there is none left for the cupellation. Believe me, I have tried it. The lead will melt, but it will never oxidize and the cupellation process will never finish. You CAN cupel in a gas furnace if you have a muffle chamber. The muffle will isolate the cupels from the combustion gas and you can allow oxygen into the muffle independent of the combustion chamber. Or, you can cupel in and electric furnace.
Gas furnaces may have more BTU's, and will therefore heat up and change temperature faster (although this does not have to be the case). Electric furnaces can be significantly less expensive. Many larger laboratories will have gas fired furnaces for the crucible fusion, and Cress electric furnaces for cupellation. They have accurate electronic digital controls to accurately control the temperature, exhaust systems, and are relatively inexpensive. You can see some popular models and details here:
http://www.Lmine.com/go.mvc?id=cress_assay_furnaces
The Cress furnaces can also be used for the crucible fusion, but the coiled elements can be damaged by any slag that spits out of the crucible.
A
Do they make a dual chamber gas furnace where you could do cuppeling in a separate chamber above the chamber where the gas is burning? I like the gas furnaces for crucible fusions but as far as cuppeling, it's electric only. Actually it would be nice to have a blower on it too to warm the garage. It would just need a blower and furnace filters to grab any dust that goes through the intake.