Ignatz61 said:
Sorry I have been away for awhile.
I was using AR instead of Straight nitric because nitric acid is a bit of a pain to make. I get 320ml out of a quadruple batch of laser steve's recipie.
in AR about 3.4ml hcl and .95ml nitric will dissolve 1gram of metal vs. 3.5ml of nitric per gram. my numbers may be a bit off but the AR uses less nitric and HCL is cheap. I have a lot of material to process so I tought I would give the AR a try. I know the results would have to be redone to get anywhere near pure.
I read here someone else was using it. I have to admit the stright nitric is a cleaner way to go, but it seems to take forever.
The problem with AR is that it reacts with any silver that may be present, forming silver chloride. If the karat value is low enough, that may not present a problem, so you'd likely experience success in the end, anyway. As you alluded, you will have particularly dirty results due to the small amount of gold present and the huge amount of base metal. The most troubling can be soft solder--which may have been the method the gold was attached to the base metal. That is likely not true in all cases.
Regards how fast the reaction works-----you can increase reaction time by incinerating the material prior to processing. That's always a good idea, anyway, to insure you don't introduce any oils or other matter that can prove troublesome in the process. When you incinerate, insure that you get the items to a low red heat. You can do it with a torch if you don't have other means to incinerate. By heating, you will help break the bonds that keep the layers fastened to one another. I may or may not help, but it certainly does no harm unless you melt the material. It's best you don't, because the gold will then be so finely divided that it may be difficult to handle until it is finally dissolved. It also helps to cut the pieces in shorter lengths, to expose edges. Unless the gold layer is on only one face, the core, which is base metal, isn't exposed to the acid, so it takes a much longer time for the core to dissolve. The layer of gold is generally thick enough that it does not get penetrated by the nitric used in the preliminary (and highly recommended) digest.
As much as you would like to avoid processing with nitric, it's in your best interest to do so. It is the method that will avoid the problems that are so typical of processing values directly in AR. That is almost never a good idea unless you have considerable experience in refining and know to watch for losses, and how to avoid them.
Even then, you should understand the process well enough that you can use the remaining base metals to eliminate the solution. That is accomplished by allowing the base metal to cement the values until the solution tests barren. It is then discarded, with fresh acid applied. By following this process, you can eliminate the vast majority of base metals from the solution. This process, too, takes a lot of time, so be patient if you would like to investigate the process. I used it on rare occasions, so I know it works, and quite well.
Luck!
Harold
