What just happened while washing gold?

I was going through Harold's washing protocol and was heating the gold in water. About an ounce of gold, 100ml water, in a 500ml beaker. It had not started to bubble. Without warning the contents of the beaker erupted violently and ejected half the gold and all of the water out of the beaker. It went all over the hot plate, all over the work table, and all over me. Thank God it was only water. I just spent an hour gathering every piece of gold I could. I am going home and will regroup tomorrow. I am still in shock and none too happy with the inevitable losses. What the heck happened :?:

A couple of possibilities.

You could have developed a hot spot under some of the gold. The beaker heats up to above the boiling point of water. When water eventually hits it, you have a steam explosion.

Or, you could have super heated it. The water needs nucleation sites for bubbles to form so it can boil. If there aren't any, the water heats above the boiling point. Eventually a bubble forms, and when it disturbs everything in the solution/beaker "system", bubbles forms everywhere all at once and you get a geyser.

Glad you're OK. Stirring helps to avoid hot spots. Boiling beads or a stirring rod can help prevent super heating.

Dave

Thanks Dave. I am glad I am OK too. My ego is bruised and I am heart sick over the loss of an unknown amount of gold especially because it isn't mine to lose.
I believe it was due to a hot spot as you suggested. Would a bed of sand in the corning dish help? I am not familiar with "boiling beads", I'll do a search on that. When you mention a stirring rod do you mean magnetic or manually operated?

Bring the temperature up more slowly will help. Give the beaker and all of the contents time to reach an equal temperature. If all you have is a hand held stir rod, use it until the boiling gets started. Keep the powders separated enough to allow the air bubble that builds up to reach the surface unimpeded. Simply put stir vigorously. Glad your not hurt, and hope you recover the lost material.

A sand bed can help by preventing direct contact between the beaker and hotplate.

Boiling beads are small glass (or other inert material) beads that you put in the beaker. They're not perfectly smooth and rounded like your beaker. Think of mis-shaped marbles. Their imperfect surfaces provide nucleation sites where bubbles can start to form.

I'm just talking about a plain glass stirring rod. It acts in the same way as boiling beads.

Dave

Did you not have it covered with a watch glass? The same thing can happen when you dry it, but without a watch glass and then that's where you can loose some. Heat slower!
I've learned the same lesson brother so don't feel alone.

Don't try to heat so quickly. Just takes patience.

It was covered but that watch glass was no match for the geyser that shot out of the beaker.
I am looking at some boiling beads online and there is a huge difference in price between borosilicate beads and flint glass beads. Will either work?
Thanks palladium, it does help to know I am not alone.

FrugalRefiner said:

A couple of possibilities.

You could have developed a hot spot under some of the gold. The beaker heats up to above the boiling point of water. When water eventually hits it, you have a steam explosion.

Or, you could have super heated it. The water needs nucleation sites for bubbles to form so it can boil. If there aren't any, the water heats above the boiling point. Eventually a bubble forms, and when it disturbs everything in the solution/beaker "system", bubbles forms everywhere all at once and you get a geyser.

Glad you're OK. Stirring helps to avoid hot spots. Boiling beads or a stirring rod can help prevent super heating.

Dave

Click to expand...

I think the second case--superheating, was more likely. I'm really sorry to hear about your experience, hope you didn't get scalded bad!

If you were using distilled or high purity water and the gold was washed well beforehand, this superheat flash boiling is a likely scenario. I'm thinking it is further compounded by the high surface area, and high heat conductivity of the gold. I guess it is a weird thermodynamic effect occurring in pure substances with a very unstable equilibrium. I have seen this happen to me with warming conductivity water in the microwave by itself--no boiling appears but yet when disturbed it rapidly boils. I can only surmise that the gold

Goran, what do you think?


and @Idahomole:
Sand bath is the preferred way to heat glassware to a uniform temperature. Just be wary not to spill precious metal solutions on it and always cover over anything on the heat or reacting. The sand will just make recovery more annoying when you do inevitably go to do it.

This is what I use to dry all my gold powders. It's useful for warming or evaporating solutions too. I find it's also good for washing gold powders, just use a small beaker with the minimum amount of water or acid for washes. It works perfect because it doesn't get hot enough to boil water. I can leave it plugged in continuously, consumes around 60W I believe. They can be found at garage sales and thrift stores for a buck or two.

Always place a weight on top of the watch glass to hold it down just in case! I use a couple of glass paper weights i picked up at a yard sale for $1. Easy to clean and chemical resistant.

In this business lessons cost money, literally! :mrgreen:

Lou, your theory is certainly plausible. I didn't get scalded, the water didn't feel that hot, but the gold had been washed a few times and I was using distilled water.

Resabed01, what is that in the picture? Is it a cup warmer for coffee or tea? I picked up a cup warmer today at a thrift store. Your post leads me to a question. You say you don't boil during washing. I don't do a hard boil but more like a simmer, a steady stream of bubbles with the hot plate just above low. Is that to much heat?

Palladium, a weight on the watch glass. I'll give that a try.

Yes, it's a coffee pot warmer. For washes, I try to get it hot as possible without boiling. Once you step up the heat to boiling, all your doing is converting liquid to gas, the solution doesn't get much hotter, maybe a few degrees but that small difference in temperature does not help with cleaning the gold powder any better.

After I licked my wounds and got back in the saddle I ended up with a 33 gram gold bar. I figure I lost about 5 grams. The bar was checked with XRF. He shot it in four different places and got .999 three times and .9999 once.
This forum rocks :!:

Way to go!! Nice and shiny!! 8)

Very nice bar. Better to lose 5 grams of gold than your sight, your health, or something else that's equally priceless.

Dave

Nice!

Were you using an induction hotplate?
Were you constantly stirring while heating?

Gold tends to clump up when they are pure, judging from your bar they are definitely pure.
My theory is, the water did not boil because you were using an induction heater, and as pure gold tends to clump up they generated enough energy to cause a spatter.

What I do when washing pure gold is there should always be constant stirring involved. I used a glass stirring rod before then switched to a magnetic stirrer. Even with this method you can see that gold will tend to shoot up once there is already enough heat.

Nice work, IdahoMole!

Looks like most all of us donate a few grams to the gold gods at some point! :lol:

That bar looks great. Congrats.