Calcium hypochlorite

[yellowfoil]

This is my first post and before I start, I would like to thank all dedicated members for very informative and caring forum. For long time, as a scrapper, I was aware of decent gold content and other values in electronics and wandered, why scrap yards had to pay for disposal of electronic waste. Times changed and about two years back, gold reclaiming became my primary hobby, which is surprisingly cheap and on the end, very rewarding. As of now, I am mainly in a gathering mode and last summer, I started to experiment with gold plated pins and gold fingers, using hydrochloric acid and bubbler. Didn’t even use the hydrogen peroxide to start the reaction. What a grate learning experience, after reading forum and then experimenting with it. With some mishaps, I managed to recover close to fourteen grams of foils. Not mentally ready for refining yet, I decided to further experiment with gold plated glass and plates. So here is my question. I used hydrochloric acid and added small amounts of sodium hypochlorite (liquid household bleach) just to dissolve some gold. When it wasn’t working any more, I added little more and so forth. Then I came across calcium hypochlorite in powder form in local hardware store. I decided to experiment with it, because it doesn’t dilute the acid. After each small addition, it started to fizzle and gold was again dissolving. So, as far as dissolving, it is working. Just wandering, if I may encounter any problem down the road, because of calcium hypochlorite. The other question is about storing, now slightly pregnant solution. Because the weather turned cold, I couldn’t continue and decided to store spent solution in a container for winter. So far it looks same as before. Ones it gets warm outside, I want to add some hypochlorite again and continue with striping. I searched for calcium hypochlorite at the forum without any success. Once again, thanks for great forum and kind help to beginners.

 

[Pantherlikher]

wow...yellowfoil... 1st time post and been here this long....good.

Haven't dug deep into calcium hypochlorite in powder form... Next on the list for glassware for me after clearing out some of these mountains of circuit boards...

I have half the shed as a make shift lab and the other is filled with material to process so it all spends the winter in the deep freeze.
Remember that acid will hold only so much before it flat out stops dissolving. When gold stops stripping from glassware for me, I filter it into a container with dirty powder to further expend acid. As I do a batch of glassware, I move solution down the line into the heat container to reduce and prep for dropping. When I give on washing endless dishes, I drop and then move into the waste stream, crock pot, that has plated crap, currently phone cord pins, hard drive ends, etc. I'll be leaving it there loosely covered all winter so as to reduce volume and such.

In the spring clean up I'll move solution into next waste bucket, start with any powder/mud from the crock and work on the next batch of what ever it is I'm stripping next.

I have my last bucket, 1/3 filled still, from 2 years ago with firewood ash to raise PH...Someday, It'll be full enough to need to process for disposal but mean time, it's slowly evaporating away...

B.S.
...calcium hypochlorite in powder form still to be tested for use...

 

[Deano]

The only area of concern using calcium hypochlorite is if your water has a lot of sulfate ions in it.

You will then get gypsum precipitating and gold losses into the gypsum.

Most town water supplies have relatively low levels of sulfate ions but there are always some local supplies which are a problem.

If you leave the solution for an extended period you will have the gold precipitate out unless you maintain the acid and hypochlorite levels.

It is easier to let the gold precipitate as it will be in the form of fine powder which is quickly and easily redissolved when you restart your processing.

You might want to look at running your leach at neutral pH with salt addition, it cuts out the chlorine fumes and most of the hydrochloric acid consumption.

Deano

 

[yellowfoil]

Thanks Pantherlikher and Deano for your insights. So far, I haven’t added any water what so ever. Solution in question is, hydrochloric acid with additions of sodium hypochlorite and later I switched to calcium hypochlorite in powder form, only. So, I should be OK with storing my solution over the winter and restarting it later, as long as I’ll avoid tap water. Acid is far from spent and I believe that there was still some chlorine in it to keep gold in solution. So far I am happy that everything is going well and do not want to complicate it, but I will consider neutral pH and salt addition later. Thanks again.

 

[Pantherlikher]

yellowfoil...
Don't bother with trying to keep it in solution or Restarting in the spring. Chlorine will gas off so it'll be tough but possible to use it more.
But why? It's not expensive to get HCL so start a fresh batch in the spring. Try your hand at dropping what's there and starting your waste stream. Learning is half the fun.

Deano, So neutral PH HCL with regular salt? Is it enough to wash the gold paint from glass?...
Have to look into that... What can keep PH neutral? Still working on testing acidic to neutral. I have tons of testers but are for fish aquariums which are high PH... And my first attempt at making wine testers didn't work at all... Must be because my sister in law only drinks expensive wine. She wasn't to keen on my wasting it soaking test strips in some...

B.S.

 

[yellowfoil]

I know that I did something out of box and don’t like it myself too much, but basically, I didn’t have much of choice. It got cold and rainy outside, and there was so little gold in the solution that probably I wouldn’t even see it on the bottom. Solution is in tight container and, considering cold weather, there is chance that some chlorine is still there. By now I managed to gather more glassware, so hopefully there is going to be more gold in the solution and plenty of time to finish it. I totally agree with you, I should have finished it. Next time I will not start project so late in the season. I hope calcium hypochlorite will work, because it doesn’t dilute hydrochloric acid at all. Thanks Pantherlikher for your input, I really appreciate it.

 

[Barren Realms 007]

I know that I did something out of box and don’t like it myself too much, but basically, I didn’t have much of choice. It got cold and rainy outside, and there was so little gold in the solution that probably I wouldn’t even see it on the bottom. Solution is in tight container and, considering cold weather, there is chance that some chlorine is still there. By now I managed to gather more glassware, so hopefully there is going to be more gold in the solution and plenty of time to finish it. I totally agree with you, I should have finished it. Next time I will not start project so late in the season. I hope calcium hypochlorite will work, because it doesn’t dilute hydrochloric acid at all. Thanks Pantherlikher for your input, I really appreciate it.

It is not a good idea to mix sodium and calcium hypochlorite, especially in an enclosed container. Mixing of the two can cause a buildup of gas that can cause the container to rupture. Pool filters have ruptured because of this same mixing of the two.

 

[Deano]

A good starting recipe for neutral pH leaching is water with 20% salt (supermarket, non-iodised) with 1% calcium hypochlorite, add HCl to pH 7.

If you do not have anything present in the leach which will consume high levels of hypochlorite, such as sulfides, then any gold in solution will stay in solution almost indefinitely.

It is only when the hypochlorite is consumed and there is a sharp drop in pH that the solution will no longer hold the gold in solution.

At that stage the hypochlorite will convert to free chlorine and offgas leaving you with no oxidant in the solution.

Deano

 

[Gratilla]

There's a mini tutorial on the hypochlorites here:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=22153&p=234215&hilit=amphoteric#p234215

Perhaps most relevant to your comments is the fact that adding water to calcium hypochlorite will produce calcium hydroxide [Ca(OH)2], a strong alkali, as a white precipitate. Adding HCl will react with this, neutralizing it without affecting the pH until the calcium hydroxide is all used up. Filtering out the calcium hydroxide first will save you a lot of HCl when adjusting pH.

 

[yellowfoil]

I would never expect, it is that complicated, but it is chemistry after all. Thanks everybody for grate insight. Now, I will have better feel and more respect for this process of dissolving gold from glassware. Absolutely will check on the container for pressure. Don’t want to see it ruptured. While glassware in solution, I noticed that gold was disappearing way above the waterline and I expected that it is caused by chlorine off gassing from the solution. One day I my try it in pressurized container to dissolve more gold in given volume. Thanks for the link.

 

[rickbb]

No, no pressurized containers.

More gasses than chlorine are given off. One of them is hydrogen and you really don't want a pressurized container of that sitting around. :shock:

 

[yellowfoil]

One have to be careful with any pressurized container, specially with chemicals inside. Probably safety valve would make it safe. For now, I will stay with open container. I was just following Geo’s post in another thread:

The solution isn't really needed to dissolve the gold. The chlorine gas will dissolve the gold without the need for the gold to be submerged in solution. Use a 4 or 6 inch piece of schedule 40 PVC pipe about three foot long. Fit the pipe with a cap on one end and a threaded clean-out on the other end. Break the material up in pieces to fill the pipe. Add 200ml's HCL. Add 50ml's house hold bleach and screw in the plug. The pipe and fittings are rated for 480 psi. It will pressurize the tube. Shake the tube up and down, back and forth a few times and leave it closed for a few hours safely away from people and pets in a secure area with the screw cap up. After a few hours time, slowly and safely unscrew the cap (always wear eye protection and other PPE's) and let the pressure off the tube. For a few cents and a little time more, add a PVC ball valve in the cap to let off the pressure. Gently rinse the material with a spray bottle of water until all the material is rinsed. The gold should be gone from the material and in solution.

Thanks for the warning.

 

[yellowfoil]

After almost a year, I would like to update every body interested on my china stripping adventure. I stored my solution over winter in container from soft drink (sticker peeled off and well marked) without any problems. This kind of plastic seems to hold pretty well and only very slight pressure developed. Over the winter, I managed to collect some china again, so I placed few cups in pyrex container and poured now slightly pregnant solution over the cups. Didn’t expect any striping before adding hypochlorite, but immediately I noticed that gold was disappearing right where the solution was poured. So I understand that there was still some chlorine in the solution and it was active. Now, I am not using calcium hypochlorite solids any more, because it tends to float and it is tricky to introduce it into solution. I went back to sodium hypochlorite in the form of liquid bleach, because it is convenient to use and readily available at my location. Calcium hypochlorite is available at pool supply and now I know it works as well. After all additions of hydrochloric acid and bleach, I ended up with around one litter of solution and decided not to precipitate yet. I have now reasonable volume of ready solution to strip more china any time I need to and do not have to waste more HCl. It used to be $10.99 a gallon in Ontario last year. About month back I decided to buy more HCl for fingers processing and surprise. It is now $14.99. So I am saving some money and don’t have to deal with additional waste. Hopefully, gold is going nowhere. Thanks for the best web site I have ever bumped to.

 

[yellowfoil]

It is year 2018 now and I still have my old solution. Didn't precipitate my gold yet, because now, after all additions I made, I have good amount of still perfectly active solution. Stored without any problems fourth year now, always ready for new gold plated glassware. Lately, I find only handful of this gold plated material in one year anyway, so mixing new solution for every few cups would be very uneconomical. Last year, I came across Lithium Hipochlorite in powder form, in pool supply department, and wonder if this chemical could be used as well. I would not mix it with my old solution, just exploring possibilities. In most places, chemicals needed for gold refining are getting scarce, and this could be just another way for people in these areas. Weather permitting, I'll try it with very small amount of solution and then I'll test it. If Stannous Chloride test will show positive, should SMB drop it as well ? Any warnings, comments or ideas would be appreciated. Thanks.