Help with HCl and Bleach

[platinumgold1776]

Hello guys! I hope you're doing well.

So, do you know how much hydrochloric acid and bleach I need to dissolve gold? Also, do you know the chemical equation of the reaction of gold, hydrochloric acid and bleach?

Thanks for reading,

platinumgold1776.

 

[kernels]

What form is the Gold in that you want to dissolve ? And how much of it.

I have been recovering Gold mainly from E-waste for a few years now, and have never really worried about how much of any chemical it takes after my first initial weeks of studying.

In your case, the bleach is the Oxidiser, so you want to use the smallest amount necessary to get the job done. An excess of HCl is not generally a problem.

So, you want to cover your material with 'enough' HCl, then add your bleach in small quantities until all the Gold is dissolved. I work with HNO3, so I don't have a good feeling for how-much bleach. With HNO3 I know that it takes very roughly a mL to dissolve a gram of Gold, double that for Copper.

 

[kernels]

It is also necessary and important to understand the effect of temperature on your reaction, while you are at it.

 

[platinumgold1776]

What form is the Gold in that you want to dissolve ? And how much of it.

I have been recovering Gold mainly from E-waste for a few years now, and have never really worried about how much of any chemical it takes after my first initial weeks of studying.

In your case, the bleach is the Oxidiser, so you want to use the smallest amount necessary to get the job done. An excess of HCl is not generally a problem.

So, you want to cover your material with 'enough' HCl, then add your bleach in small quantities until all the Gold is dissolved. I work with HNO3, so I don't have a good feeling for how-much bleach. With HNO3 I know that it takes very roughly a mL to dissolve a gram of Gold, double that for Copper.

It's gold powder, and it's just 20 grams.

 

[kernels]

Cool, this thread -> https://goldrefiningforum.com/phpBB3/viewtopic.php?t=24229 probably holds the answers you seek.

 

[butcher]

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=6208&hilit=how+much+bleach
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=15964&p=160778&hilit=how+much+bleach#p160778
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=15913&p=160231&hilit=how+much+bleach#p160231
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=16713&p=168959&hilit=how+much+bleach#p168959
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=8931&p=180530&hilit=how+much+bleach#p180530

 

[platinumgold1776]

Thank you two!

 

[butcher]

2Au + 6HCl + 3NaClO --> 2AuCl3 + 3NaCl + 3H2O
From the equation theoretically, two moles of gold (2 x 196.97 grams) or 393.94 grams of gold will react with six moles of HCl acid (6 x 36.46g) or 218.77 grams of HCl and three moles of sodium hypochlorite (3 x 0.0134g) or 0.0402 grams of NaClO -------> to yield two moles of gold chloride (2 x 303.325g ) or 606.65 grams of AuCl3 and three moles of table salt (3 x 58.44g) or 175.33 grams of NaCl, in three moles of water (3 X 18.02g) or 54.06 grams of H2O.

Now if we can only keep our solutions within the parameters of that equation we could expect a similar reaction.
But our mileage and or solution will not always go by the book, here there are a lot of different factors, pH is a major factor with this solution, temperature, how long we can keep chlorine gas in the solution, the physical size of the gold, base metals involved, the list goes on and on...

 

[platinumgold1776]

2Au + 6HCl + 3NaClO --> 2AuCl3 + 3NaCl + 3H2O
From the equation theoretically, two moles of gold (2 x 196.97 grams) or 393.94 grams of gold will react with six moles of HCl acid (6 x 36.46g) or 218.77 grams of HCl and three moles of sodium hypochlorite (3 x 0.0134g) or 0.0402 grams of NaClO -------> to yield two moles of gold chloride (2 x 303.325g ) or 606.65 grams of AuCl3 and three moles of table salt (3 x 58.44g) or 175.33 grams of NaCl, in three moles of water (3 X 18.02g) or 54.06 grams of H2O.

Now if we can only keep our solutions within the parameters of that equation we could expect a similar reaction.
But our mileage and or solution will not always go by the book, here there are a lot of different factors, pH is a major factor with this solution, temperature, how long we can keep chlorine gas in the solution, the physical size of the gold, base metals involved, the list goes on and on...

And the ratio of hydrochloric acid to bleach would be 3:1?

Thanks for reading,

platinumgold1776

 

[g_axelsson]

If you mix it in that ratio then you will fail. HCl + bleach will produce chlorine gas and you could only absorb some of it in the liquid, the rest goes off as gas. Add small increments, stir and let it work for a while. When you think it stopped working, add a dab more... until all gold is dissolved.

I've never measured the volume of bleach I used when I tried that method, just added it by feeling and by observing the reaction until the work was done. I've only used it on foils from electronics and redissolving fine gold powder when re-refining gold.

Göran

 

[platinumgold1776]

If you mix it in that ratio then you will fail. HCl + bleach will produce chlorine gas and you could only absorb some of it in the liquid, the rest goes off as gas. Add small increments, stir and let it work for a while. When you think it stopped working, add a dab more... until all gold is dissolved.

I've never measured the volume of bleach I used when I tried that method, just added it by feeling and by observing the reaction until the work was done. I've only used it on foils from electronics and redissolving fine gold powder when re-refining gold.

Göran

Thanks for answering, but what would be the ratio I need to produce a stoichiometric equation?

Because, I read the Gold Refining Forum's handbook and it says that I should put hydrochloric acid and bleach in a ratio of 4:1

Please help, I'm confused.

platinumgold1776.

 

[FrugalRefiner]

Understand that the Forum Handbooks were created years ago from posts at that time. We have learned a lot since then. It suggests adding glycerine in a sulfuric stripping cell. It is not needed. It suggests much higher amounts of H₂O₂ when starting the AP process. Only a capful is needed. We now understand more about how the HCl and bleach process works. There is no stoichiometric amount because no matter how you add the bleach there are going to be losses as chlorine gasses off and you always want excess HCl.

Follow Göran's advice. Add a bit, stir, and let it work. When the reaction stops, if there is still gold left, add a bit more, stir, and let it work.

Dave

 

[platinumgold1776]

Understand that the Forum Handbooks were created years ago from posts at that time. We have learned a lot since then. It suggests adding glycerine in a sulfuric stripping cell. It is not needed. It suggests much higher amounts of H₂O₂ when starting the AP process. Only a capful is needed. We now understand more about how the HCl and bleach process works. There is no stoichiometric amount because no matter how you add the bleach there are going to be losses as chlorine gasses off and you always want excess HCl.

Follow Göran's advice. Add a bit, stir, and let it work. When the reaction stops, if there is still gold left, add a bit more, stir, and let it work.

Dave

And the final product would be AuCl3 or HAuCl4? Can I dissolve platinum with bleach and hydrochloric acid? If so, is there an equation for that reaction?

Thank you for reading,

platinumgold1776.

 

[butcher]

And the final product would be AuCl3 or HAuCl4?
It would depend on the acidity of the solution and the oxidation state of the gold in solution.

Can I dissolve platinum with bleach and hydrochloric acid?
It can attack platinum, but not effectively, it struggles to dissolve gold foils

If so, is there an equation for that reaction?
Sure you can write a reaction for just about anything, just plug in the values and do some figuring.

 

[platinumgold1776]

I'm glad you could help me, thank you all.