Help with hydrochloric bleach method

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icejj

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Feb 19, 2021
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I decided to try dissolving a small amount of gold foils with the HCL bleach method. Mainly to test this method out, as I may want to use such method on a larger batch if I can perform it successfully. I feel as if I added too much bleach and now some type of solid has formed that I can't dissolve. I'm assuming the solid is a type of salt? I tried adding more HCL to dissolve it. That did not work. I've also tried adding water to dissolve it. That did not work either. Can someone provide clarity as to what I should do next? Can someone provide clarity as to why the solid wouldn't dissolve when adding more water/hcl?
 
Here are pictures of the solids, I forgot to attach them to the first post
 

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Hard to tell. Bleach is commercial product, maybe some other stuff than NaClO and NaCl were present... Filter and proceed further, i would say :) And try other brand of the bleach next time. Maybe it is just contamined.
 
Hard to tell. Bleach is commercial product, maybe some other stuff than NaClO and NaCl were present... Filter and proceed further, i would say :) And try other brand of the bleach next time. Maybe it is just contamined.
The solids started off as fluffy looking clouds after adding bleach to HCL and foils, then as I started evaporating the solution, the fluff began to take a different form until they turned into tiny little soft rocks... does that help any? Lol
 
How much bleech did you add to how much HCL?
HCL is pH 1, bleech is pH 11. So depending on how much bleech you added, hydroxides maybe? Salt crystals?
Test the Ph, test with stannous, and if Ph is high, add HCL if pH is higher than 2 or 3, i think.

When in doubt, cement it out. Filter first.
 
How much bleech did you add to how much HCL?
HCL is pH 1, bleech is pH 11. So depending on how much bleech you added, hydroxides maybe? Salt crystals?
Test the Ph, test with stannous, and if Ph is high, add HCL if pH is higher than 2 or 3, i think.

When in doubt, cement it out. Filter first.
It was about 50ml-75ml of bleach to 200ml HCL. Not too sure on the exact amount but it was around that range. I'll test the ph soon. The stannous test was positive for gold.
 
The solids started off as fluffy looking clouds after adding bleach to HCL and foils, then as I started evaporating the solution, the fluff began to take a different form until they turned into tiny little soft rocks... does that help any? Lol
Impurity can get inside from HCl, bleach or foils. There is no other feed into the reaction.
HCl is often fairly contamination free, except some dissolved iron (yellowish discoloration of technical stuff).
Bleach, I don´t know. It is made by electrolysis of NaCl solution or by passing stream of chlorine through solution of NaOH. There is not very much possible impurities from the production process, aside of minor metal contamination, if it was electrolyzed. Problem is, that Clorox or any other brand could add some stabilizers or other chemicals to it. This could pose a problem. And impurities are completely unknown.
Third possibility is contamination from foils. Lacquer, some polymer junk coating etc is one possibility. Some low solubility metal precipitate is the other. Tin compounds form fluffy voluminous oxochlorides when tin (II) in solution meet oxidizer. It could also aglomerate to form some better packed precipitate. From the photo it does not quite look as Sn(IV)OxClx stuff...

XRF would be helpful in way to identify the impurity, but I am maybe "over-analytical" :D filter and proceed further.

Just to note, bleach is quite ineffective oxidant for dissolution of gold. Chlorine escape from the reaction vessel quite quickly - so you will need to add quite a bit of bleach, which itself is also very diluted (5-13% - and never trust the label, it´s always less :D bleach decompose slowly over time). If you want to improve the efficiency of chlorine adsorption, take thin tubing (like for medical use) and dose the bleach slowly under the level of solution (best from the bottom). Use taller beaker, so the column of liquid escaping gas need to pass is greater. And do not overshoot with temperature.
It might take longer to dissolve at room temperature, but you use less bleach to accomplish the dissolving.
Also cover the beaker with some plastic wrap or watchglass, round bottomed flask etc. to eliminate evaporation loss of chlorine.
If it is possible for you, purchase what is called here "shock pool chlorine" which is practically granulated calcium hypochlorite (check the label). It is relatively cheap (i managed to get 700g for like 6 EUR in local supermarket pool section) and quite soluble in water. You can make as strong as 20% solution, and best is it does not decompose over time nearly as bad as aqueous bleach.

Be careful, one good accidental whiff of chlorine and you could end practically disabled for life. Do not take any chances :)

Stay safe
I wish sucessful refining
 
As Orvi said just filter any junk out and precipitate the gold , if you have any values left on your filter you will recover them when you process you old filter papers.
Some bleach have perfumes etc and again as Orvi pointed out they can cause these results but I really wouldn’t worry .
 
Impurity can get inside from HCl, bleach or foils. There is no other feed into the reaction.
HCl is often fairly contamination free, except some dissolved iron (yellowish discoloration of technical stuff).
Bleach, I don´t know. It is made by electrolysis of NaCl solution or by passing stream of chlorine through solution of NaOH. There is not very much possible impurities from the production process, aside of minor metal contamination, if it was electrolyzed. Problem is, that Clorox or any other brand could add some stabilizers or other chemicals to it. This could pose a problem. And impurities are completely unknown.
Third possibility is contamination from foils. Lacquer, some polymer junk coating etc is one possibility. Some low solubility metal precipitate is the other. Tin compounds form fluffy voluminous oxochlorides when tin (II) in solution meet oxidizer. It could also aglomerate to form some better packed precipitate. From the photo it does not quite look as Sn(IV)OxClx stuff...

XRF would be helpful in way to identify the impurity, but I am maybe "over-analytical" :D filter and proceed further.

Just to note, bleach is quite ineffective oxidant for dissolution of gold. Chlorine escape from the reaction vessel quite quickly - so you will need to add quite a bit of bleach, which itself is also very diluted (5-13% - and never trust the label, it´s always less :D bleach decompose slowly over time). If you want to improve the efficiency of chlorine adsorption, take thin tubing (like for medical use) and dose the bleach slowly under the level of solution (best from the bottom). Use taller beaker, so the column of liquid escaping gas need to pass is greater. And do not overshoot with temperature.
It might take longer to dissolve at room temperature, but you use less bleach to accomplish the dissolving.
Also cover the beaker with some plastic wrap or watchglass, round bottomed flask etc. to eliminate evaporation loss of chlorine.
If it is possible for you, purchase what is called here "shock pool chlorine" which is practically granulated calcium hypochlorite (check the label). It is relatively cheap (i managed to get 700g for like 6 EUR in local supermarket pool section) and quite soluble in water. You can make as strong as 20% solution, and best is it does not decompose over time nearly as bad as aqueous bleach.

Be careful, one good accidental whiff of chlorine and you could end practically disabled for life. Do not take any chances :)

Stay safe
I wish sucessful refining
Thanks for the info! I'm going to filter and finish the process.
 
As Orvi said just filter any junk out and precipitate the gold , if you have any values left on your filter you will recover them when you process you old filter papers.
Some bleach have perfumes etc and again as Orvi pointed out they can cause these results but I really wouldn’t worry .
Thanks!
 
I just successfully completed the HCL - bleach method to dissolve some gold foils. Should I denox with salfamic acid before proceeding?
Please try to get your names for the Chemicals correct. One letter difference in the name can make a huge difference.
And no, you only use Sulfamic acid for solutions with Nitric or Nitrates in them.
Just give a good heat close to boiling and let it rest.
Just make sure it is acidic before you precipitate the Gold.
 
I just successfully completed the HCL - bleach method to dissolve some gold foils. Should I denox with salfamic acid before proceeding?
SO2 gas generated from SMB addition will easily kill all dissolved chlorine gas. It is wise to slightly heat the open beaker to remove chlorine by evaporation, then you will consume less SMB.
Sulfamic addition can worsen the situation, as chlorination of sulfamic's nitrogen could be the real issue.
 
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