Ed,
I haven't incinerated anything yet. I'm pretty sure I had all the HCl out. I rinsed with boiling water 3 times.
Say I wanted to remove tin with HCl, and then I think I could "wash out the HCl out" with boiling hot water, then I decided to remove some copper from my gold, but I was not ready to dissolve my gold yet, what would happen if I went straight to nitric acid now?
You cannot just wash the effects of HCl out, not only would their be traces of HCl (especially if powders), but there will be metal salts of the HCl, these metal chlorides, when come into contact with hydrogen from an acid (like hydrogen in HNO3) would convert back to HCl, now I will have some HCl mixed with my HNO3, so I will dissolve some gold.
This is one reason we incinerate, when changing from HCl to nitric (to dissolve base metals), to remove the HCl or convert the base metal chloride salts to metal oxides.
silver chloride is volatile, if heated strongly like when incinerating or roasting the powder to red hot (or melting), and much of the silver will burn off going up in the white smoke, gold when incinerated with chloride salts, some of the gold can also become volatile as in these temperature gold chlorides can form from the chlorides burning off chlorine gas, some gold can be lost with this gas, usually leaving yellow stains where it condensates to cooler surfaces, sometimes purple stains can be notices where tin condensates also, to try and convert the chloride salts to hydroxides then oxides, and to remove some acidity I will usually give my powders a wash in a solution of sodium hydroxide and rinse the sodium chloride salts well with water, drying and crushing, before incinerating.
If I understand correctly, adding HCl to the Nitric/water solution will use up the excess Nitric? Right now I have a little less than 100 ml of the 50/50 Nitric/water solution. The blue color hasn't darkened any further & no more of the "scum" has digested after sitting over night. After I decant, will another 100 ml of HCl be enough to DeNox? I wish I had my own computer, docs, etc... I had this pretty much all figured out. Or so I thought.
Adding HCl to nitric/water solution will not use up the nitric or it will not use up the HCl, but it does form some gases nitrosyl chloride NOCl , nitrogen dioxide NO2, nitrogen oxide NO, chlorine Cl2, these gases will react with metals in solutions some will leave the acid solution and some will mix with the acid, if water is involved some of these gases will stay in solution but can convert back to acid, if dilute and cold these cases stay in solution much longer, these gases are also important in solution when we make aqua regia to dissolve gold, this is why we do not premix aqua regia before we are ready to use it.
So mixing HCl into nitric does not DeNOx, it just makes aqua regia, so it will not use up nitric acid.
What can use up nitric is its action on oxidizing metals, in Aqua regia the nitric oxidizes gold along with the strong gases mentioned above, so we can use up HNO3 by dissolving gold (and actually we could use up our HCl, if we did not add an excess like we do), (Note if we had more nitric in solution and had a limited amount of HCl, we could actually use up all of the HCl and then we could not dissolve more gold, what gold we did have would be dissolved in the solution of excess nitric acid), heat can also assist in using up the acid the acids reaction can slow or seem to stop in cool or cold solutions, when heated these same solutions can still dissolve a lot more metals, and concentrating the solution the solution will dissolve more, also a hot solution can hold more metals in it that the same solution if it is cold…
Heat can be not only extremely useful, but many time just downright a necessity.
How much heat I say really usually depends on the process, what stage of that process, and the reason for the heat, or the reason to lower the heat.
Hardly ever do you boil a solution.
You never want to boil a solution of aqua regia with dissolved gold.
Sometime I may bring a solution up to almost boiling and hold it there, then lower the heat to let powders settle well which may take some time, with the goal of keeping the solution as hot as possible, but also not so hot that it stirs the powders, I may do this when I am using boiling hot water to dissolve the lead chloride salts from silver chloride salts, when the very fluffy insoluble silver chloride settles, I will decant the soluble (in very hot water only) lead chloride.
Sometimes I may to measure how hot a solution is and I may need to control the temperature within a certain range for best results, or the temperature can be indications as to what I have or what is happening, like when distilling solutions.
Sometimes I cannot heat a solution as much as I would like to and I have to settle for using a very slow low heat, making the process seem to take forever, like when drying meal powders before being able to incinerate, where if I raise the heat too high gas bubble rising to the surface of the metal mud will sputter and spit my mud all over the place.
Sometimes I may be able to evaporate my aqua regia below boiling, but have to watch it closely as it concentrates, as there is a point in concentration where nitric gasses wanting to come out of solution in mass or all at once, if you kept the temperature this high the pot will boil over foaming all of your gold out of your pot, you can see tiny bubbles form around the edge of the solution just before this happens and you can lower the heat until you are past this point, then you can raise the heat again, (after you lose your gold and have to process 5 gallon pail of dirt and leaves, to get some of that gold back, you will have learned a couple of lessons, like to keep an eye on your aqua regia when evaporating watch for the bubbles in concentrated solution and or lower heat, catch basins are easier to clean up than the dirt, and trying to get your gold back out of the dirt is no fun at all.
I guess what temperature to use is one of those things you will learn not only with study but also by doing.
I do not know how much gold you may have in the solution, you do not either unless you test it, gold is rare, so you really want to keep all of it you can, stock pots are a great precious metal trap, for traces, a great piggy bank, every refiner needs a good penny bank, as sometimes those penny's can mean whether you make a profit or go broke.
We all learn from our mistakes, but it is better to learn as much as we can through study, so that we are not just learning to make more or better mistakes, mistakes yes we can learn from them, but if this is all we learn from, that can very well be all we get good at, is making mistakes, and believe me when I say mistakes are very costly, so studying and getting a better understanding can help us learn to make less mistakes, study and practice can help us to understand better not only how not to make mistakes, or prevent them, but also how to fix them when we do.
Ed, I hope this helps and you get that computer going.
To me when something is reduced, it loses something.
