Now sulfamic acid is bad as well?

Just bought it at home depot the other day....couldn't seem to get it to kill excess nitric acid in an AR solution.

Today I mixed 10 mL of HCl, 2 mL of Nitric (70%) and 24 mL distilled H20.

Upon addition of sulfamic crystals....nothing.

I've read numerous accounts of sulfamic pretty much working in all forms, hot/cold/dissolved/crystal/etc. Just add it and expect a violent reaction that gets more violent upon stirring.

So am I right in assuming that this stuff is...well, I don't even know what to call it.

You probably diluted the solution to the point that the reaction wasn't visible. Just my guess.

Edit to ask: Did you heat the solution?

Sulfamic at home depot? How pure is it?
Maybe it wasn't sealed? It tends to lose its ability to neutralize acid when left at open air. And it is endothermic so you need to heat the solution.

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autumnwillow said:

Sulfamic at home depot? How pure is it?
Maybe it wasn't sealed? It tends to lose its ability to neutralize acid when left at open air. And it is endothermic so you need to heat the solution.

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It's where I get mine, it's called ceramic tile cleaner and is labeled 100% sulfamic acid. I agree with it needing heat, I've always used it when the AR was still warm, never had an issue with it not showing a reaction.

Yeah, this stuff must be bad. Tried heating it in nitric and got nothing.

I could tell the packaging was old, as it had dust on it.

Thanks!

You wouldn't need it if you would learn how to never use an excess of nitric.

goldsilverpro said:

You wouldn't need it if you would learn how to never use an excess of nitric.

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It's true...but I think that comes with experience.

I'm processing a half pound of chips (broken in half), and adding nitric ~3 mL at a time.

It's tricky to determine when the copper traces inside the ceramic chip are digested.

If you have suggestions, I'm all ears.

I'll offer a couple, if you will accept them from a mere KNO3 user.

In case you're not already, do it "very warm".
For a 1/2 lb of chips, I'd be thinking a little less nitric per addition. Maybe reduce to 1ml or less, especially as you feel you are coming close.

Since I only use AR on karat scrap I like to use the sulfamic in case any of the scrap has some lead in it.

jason_recliner said:

I'll offer a couple, if you will accept them from a mere KNO3 user.

Click to expand...

Bah...a little different equation but same answer.

Yes, it's warmed. On my first addition I heat until I get what I think is excessive bubbling (boiling) then back the heat off.

I'll drop down to 1 mL next time.

My biggest problem isn't the addition size, it's the end of reaction. I've pulled a couple reactions early due to no more gas production following nitric addition, only to find that there was still copper present. Not a big deal to start another batch of AR, but annoying nonetheless. I've been just breaking chips in half, I think I need to crush a little finer as I think it's taking the nitric too long to get through the channels to the copper traces.

I want to get my shop moved, so I can finish my ball mill.

Have you tried alternating the acid additions?
It may have needed a little HCl to kick off the reaction again.

Sometimes I just leach as much as the acid will work, decant (carefully, leaving all solids) then start with fresh acid, as it works slower when saturated.

I actually realized that when I was typign the response, that I never tried adding some fresh HCl.

I also need to just inquart the karat scrap I have so that I'll have a good sized button to do any denoxxing. Plus I've got some earrings from goodwill that need to be tested.

I've been trying to put it all off until I get the garage clean and organized. But then I get the bug.