Refining Rhodium

all right everyone welcome back to Cody's lab so for some of my upcoming projects I need some rhodium metal I'm going to be using it primarily as an alloying ingredient but also as a catalyst I kind of want to try some of that out rhodium has some very interesting chemistry so I recently went and I bought a sample so you can see it here in this bottle see but you might notice that some of the pieces in here are gold colored rhodium is a silvery white metal it is very shiny but some of the pieces in here are very much yellow and that's because they are in fact gold this sample of rhodium is contaminated it's contaminated with gold this is because it was used in an electroplating bath so this came from a company that did some electroplating on some jewelry and other items so they would put the items on a wire basket and then lowered into an electroplating bath and they did both gold and rhodium and this means that uh the wire mesh of the basket would get plated along with the items and the basket would get reused and they eventually broke the pieces of metal off the basket and sold it to me this is the cheapest way that I could get rhodium but it does mean that it's impure and I will need to purify it So today we're going to be some refining some rhodium all right here we are out in the lab as you can see we'll be working inside the fume Hood which I have renovated since we were last here so here's my sampler metal I'll be working with first thing I need to do is weigh it and see how much I've got okay that's 4.65 grams [Music] so now I'm going to essentially grind the material up into a fine powder the reason for that is just make Chemical Reactions happen faster anything I can do to speed things along will help because neither one of these metals are particularly chemically active so what I'm going to do is I'm going to make an alloy of it with some zinc as you can see here I'm going to put in about 10 times the mass of the metal of zinc this is because even a small amount of rhodium in an alloy of zinc will greatly increase the melting point and I need the zinc to be a liquid below the temperature that zinc boils so that means I need to keep the percentage of rhodium down below about 10 percent [Music] back to a little higher probably isn't a bad idea there we go next I'm going to add some flux so I've got some dry borax here which I'll add this will protect the zinc from oxidizing as I melt it in the furnace okay [Music] let's put this in the furnace that and I'm going to heat it to just below the boiling point of zinc [Music] all right furnaces come up to temperature 1508 degrees Fahrenheit let's open this up and have a look everything's melty it's good breakage or anything I'm going to give this a stir with a piece of wire make sure everything's mixed so the metal is properly all the way together I'm going to stir it too very soon disturb the flux because the zinc is very reactive right yeah it's looking pretty good just to let that sit for a minute hopefully those little bits of metal you can see floating in the flux will settle out and we'll just let it cool okay so I just let it cool off in The Crucible because if I were to try to have poured it while it was hot the zinc would have caught fire and everything would have burned up into smoke it does mean I'm gonna have to destroy The Crucible but these things are like two dollars each it's not a big deal just gonna break it [Music] foreign there it is and this stuff might contain some rhodium so I will save it process it later [Music] swag here [Music] so now I'm going to dissolve the zinc to do that I'm going to make a dilute solution of nitric acid which will dissolve the zinc turning it into soluble zinc nitrate this should also dissolve any nickel or Palladium that might also be present a little bit of electric acid solution let that dissolve overnight see it making the hydrogen gas this will of course leave the gold and rhodium behind it should be in the form of a very fine color so there it is dissolving you see these uh black particles are coming off that's the golden rhodium let's let this continue up until it's all finished so here we are it's the next day all the zinc has been dissolved and I'm left with a fine grayish black powder of rhodium and gold I'll just decant the liquid solution wash it with water a couple of times and we'll have our powdered metals [Music] okay there we are just dried out [Music] foreign [Music] so now that the metal has been converted to a fine powder I'm going to chemically separate them ideally I would dissolve one and leave the other behind both of these metals are very difficult to dissolve though a mixture of strong acids is needed to dissolve gold for instance but that also slowly dissolves the rhodium and I'd really rather not attempt to separate the two once in solution I think I could but I don't know what happened it'd require a lot more research on my part one of my first ideas was to dissolve the gold out using some Mercury Mercury will dissolve gold but does not affect rhodium the issue with that is mercury doesn't dissolve a lot of gold it's like a few parts per thousand unless it's very hot and I've been trying to avoid poisoning myself so this is out at least for now my next thought was to use sulfuric acid when concentrated and near its boiling point sulfuric acid will dissolve rhodium it also slowly dissolves gold so same problem as the Ocarina I do think that the sulfuric acid is the right idea though I just need something that is chemically similar but not as aggressive so by sulfate this will decompose upon heating to pyrosulfate and in the liquid state that will dissolve rhodium and I've confirmed it does not dissolve gold I will be using the potassium salt for its wider liquid range and I've also pre-decomposed the bisulfate to the pyrosulfate this is so it doesn't produce water and bubble over inside the furnace also it is an important step to thoroughly mix them together before adding to the furnace because the metal powder on its own tends to Clump up and if you're trying to break up the clumps while it's hot inside the furnace you could possibly tip over The Crucible and spill it out guess how I know that [Music] put that in there there we are the furnace is up to temperature and see how it's doing pyrosulfate has melted and it looks like foaming a little bit decomposing into uh sulfur trioxide and potassium sulfate which won't dissolve the rhodium so I'm actually gonna back off the heat a little yeah that looks pretty good the uh I don't know how well that's coming up in the video but it's kind of a dark orange color indicates that the rhodium is dissolving so I'll just let this cook for perhaps a few hours and I'll come back and uh continue working on it since I have some room in The Crucible I'm going to add some more of the pyrosulfate so I've let this go for over six hours probably doesn't need to go that long that that's what I did so let's uh pull this out pour off the material yes it's got that nice dark reddish orange color lots of dissolved rhodium in it lovely it's not that cool [Music] so now that it's cool I'm gonna put it into a beaker and dissolve it in water put in enough water to cover it yep and warm it up so it dissolves faster [Music] foreign [Music] there it is ready for the filter here so now I've got the rhodium in an aqueous solution awesome if you look at the powder it's left in the beaker you can see it is a yellow brown instead of the black that it was because I removed rhodium from it and you can see the gold there's probably some rhodium in there still and in order to wring out the rest of it I'm going to have to essentially repeat this whole process put it in the furnace with some zinc dissolve the zinc and acid the hole works might even have to do that two or three times I'm not going to do that today we're just gonna focus on what I've got dissolved here [Music] it's uh convert this back into rhodium metal so I've moved this so I've moved the solution over to another Beaker which I'm going to put on a hot plate and begin Heating and to this I'm going to add some formic acid approximately 30 milliliters worth for this much so about 10 of these there you go and I'm also going to add some ammonium chloride four or five heaping tablespoons there we are give this a mix let it heat up [Music] no no you can't be in here no there we are I've got the rhodium to precipitate there it is I'm gonna pour off the liquid and uh I'm definitely gonna save it because I don't think I've precipitated all of the rhodium I'll just use zinc to drop out anything that's left but should have at least a little bit pure rhodium emphasis on a little bit listen I was hoping but anyway rinse it with some water foreign truth about a third of a gram okay put this in a bottle so there we are a third of a gram of pure enough for my needs rhodium powder so I was kind of hoping for at least a gram but you know this is not all of it I'm still going to reprocess it and I will of course get more but as a good start I learned loads doing this and perhaps I'll do a part two when I get a process that's maybe a little bit more efficient uh I'm not going to melt this down into a metal I think I could but it's worth more to me as a powder as is so maybe if I get more I'll I'll try to get it into a bead but for now this is good this is what I needed so hope you enjoyed I'll see you next time

Channel: Cody'sLab

Views: 608,837

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Id: ZySV8j7c5Vk

Length: 17min 54sec (1074 seconds)

Published: Thu Mar 02 2023