General Reaction List

[lala14]

Potassium dichromate, K2Cr2O7, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is potentially harmful to health and must be handled and disposed of appropriately. It is a crystalline ionic solid with a very bright, red-orange color. It is also known as potassium bichromate; bichromate of potash; dipotassium dichromate; dichromic acid, dipotassium salt; chromic acid, dipotassium salt; and lopezite.

Potassium dichromate (oxidizing agent). The reduction half-equation can be seen:

Cr2O72−(aq) + 14H+ + 6e− → 2Cr3+(aq) + 7H2O (E = +1.23 V)

compared with potassium permanganate. It is used to oxidize alcohols. It converts primary alcohols into aldehydes, or into carboxylic acids if heated under reflux. In contrast, with permanganate, carboxylic acids are the sole products. Secondary alcohols are converted into ketones — no further oxidation is possible. For example, menthone may be prepared by oxidation of menthol with acidified dichromate. Tertiary alcohols are not oxidized by potassium dichromate.

its not to strong to use as it is but if want to reduce its value i would reduce to 80ml of distilled water \not 100mml 500ml of course you can make it but i heard its good stuff to dissolve gold an drop with smb or sb or magnesium but drops all the metals dissolved then you have a mess but good luck


d[-_-]b jesse

 

[steyr223]

Excellent post Steve.
You put together a cheat sheet that I have.been working
On for almostt 4 months

Thanks

 

[kj13]

my aqua regia turned red, and wont precipitate...help

 

[Oz]

Well no one can help you without more detail. How much of what were you trying to digest would be a good start. What have you added besides hydrochloric acid and nitric?

 

[kj13]

I would like to know if anyone knows why some reasons on why my aqua Regia has turned red and everytime I add precipatant I get a red foam instead of a nice blue. Please replay, I need to get the Gold Chloride to solidify
:|

 

[kj13]

I would like to know if anyone knows why some reasons on why my aqua Regia has turned red and everytime I add precipatant I get a red foam instead of a nice blue. Please replay, I need to get the Gold Chloride to solidify
:|

I was try to digest 187 grams of a mix of scrap 14 and 10 k I still have gold chloride that is still testing positive, I dont want to add to much precipatant, I added urea and it appears that a cycle of precipatate and digestion is occuring.

 

[Oz]

Aqua regia usually turns red when you have a decent concentration of gold or platinum. I have never seen blue foam on aqua regia when I precipitate gold.

You still have free nitric in your solution. It is a common mistake using too much.

 

[AndyWilliams]

I've posted this before, but can't seem to locate it now.

Chemical formula of reaction between gold and sodium meta bisulfite:

Sodium Meta Bisulfite + Water = sodium bisulfite

Na2S2O5 + H20 --> 2NaHSO3

then we precipitate gold:

sodium bisulfite + auric chloride + water = sodium bisulfate + hydrochloric acid + gold

3 NaHSO3 + 2 AuCl3 + 3 H2O --> 3 NaHSO4 + 6 HCl + 2 Au

Steve

Uh oh, I think I just understood my first chemical reaction! Maybe. . .

 

[Harold_V]

I would like to know if anyone knows why some reasons on why my aqua Regia has turned red and everytime I add precipatant I get a red foam instead of a nice blue. Please replay, I need to get the Gold Chloride to solidify
:|

You have made a request two times, each time providing absolutely no information that might help someone provide some guidance. Why is that?

Harold

 

[butcher]

Lately we have many questions from new members wanting to learn the processes we use.

I have not read the general reaction list for several years.

But I have been referring new members to read it.

Today I spent a little time scrolling through the general reaction list and the organized links to other information that Laser Steve has so well put together.

I have read most all of this over the years and understand it, I am amazed at the work and thinking that Steve has put into doing this.

Any new member should spend some time reading and following this thread and links, it would help them in understanding the process.

New Members Go back to page one of this thread and read through it, also follow the links in the general reaction list by clicking your mouse on them, these links lead you to more information with even more links, so by using the back button, to get back to where you were in the general reaction list, Steve has done an excellent job of linking together this very helpful information.

Here is a link to more:
http://goldrecovery.us/forum_search.asp

Thank you Laser Steve, you have done a lot of work to help all of us here on the forum.

 

[lazersteve]

Butcher,

Thank you for the compliment. What many old and new members alike don't understand is that the posts in the Guided Tour where carefully choosen to help everyone navigate the ever increasing size of the forum as it grows. It never ceases to amaze me how many times noobs are asking questions that have been answered over and over again. I know Ralph made a few versions of the 'GRF Handbook', but I have made many changes to the original posts of mine that he has included in that book. Everyone wants a 'drive thru' answers booth without putting in the real hard work required to learn not just how to do the reactions, but why they are happening the way they do, and what variables affect the outcome. Once they learn the basics, they forget to look back to where they learned the information from to refresh and renew what they have studied in the past.

It seems the forum has turned into a new group of 'instructors' who are merely teaching from the same old material that has been here since the early years. I personally have tried to continually refer members with questions back to the original content when possible, as opposed to repeating the same information over and over again. This serves several purposes, mainly to keep the size of the forum down and to give the proper credit to those who posted the original answers in the beginning. I would venture to say that over two thirds of the answers to common recovery and refining questions were answered in the first year the forum was open to the public.

I owe a big debt of gratitude to Harold and Chris (Goldsilverpro) for the helping hands they have extended to me over the first year of my membership here. I want to thank Lou for trading me for lab quality samples of the PGMs to hone my PGM skills. I also want to make special mention of all of the members who have taken the time to put in the hard work required to grow to the point of being able to contribute real content to the forum. It seems that the forum these days is full of so much 'chatter' that it is hard to find the wheat in all the chaff. I only hope I have succeeded in returning the favor to everyone for what I have gained here. Lastly, I strive to never forget my roots when it comes to learning.

Steve

 

[Lou]

Thank you very much, Steve.

I am very glad that you have been able to bring as much accessible knowledge about extractive PGM hydrometallurgy to the forum and the general public at large, and done so in a way that is both technically correct and easier to chew for those without extensive chemical backgrounds.


Likewise, I also owe Steve, and all of the other moderators as well as the forum at large quite a bit of gratitude for the things I've learned from them, the business that some of us have conducted, and, most important, the friends I have made.

 

[malfeces]

I am speechless. Rereading over and over... This is phenomonal info...
Thanks LS!

 

[goldsilverpro]

Thanks, Steve. I really appreciate what you said.

This is a game of knowledge and experience and no one on the planet knows it all. I did it professionally for most of my life but, if the truth were known, I have probably learned at least as much during my 5+ years on the forum. Not only from the moderators but from many, many of the regular members. Not a day goes by when I don't learn something new.

 

[Anonymous]

6. H2SO4= Sulfuric Acid = 1 cup 96%+ Sulfuric, 1/8 tsp glycerin (optional). Used as electrolyte in electrolytic cell along with a small amount of glycerin. Effective on medium to large gold plated items. With specially designed anodes and cathodes large batches of smaller plated items can be processed. Not used for Gold filled or karat jewelry.

Use until acid is saturated with black powder typically 12-24 hours of operation. Sink any floating black powder, let settle overnight, pour off bulk of acid for reuse, and dilute remaining acid with 4 parts water

I have my cell setup and ready to start stripping gold plated pins. But I have a few questions I'd like to ask you Steve.

No# 1. I see that the glycerin is optional, but what is the reason for adding it to the Sulfuric Acid?
No# 2. Do the Sulfuric Acid have to be 96%+? or will a lower strength just take longer to deplate the pins?
No# 3. Is the forming of the thick sludge/mud the indication that the solution has been used to its capacity?
No# 4. How many batches should I run after a single batch batch has started, as to not over-heat the charger and the pyrex? Let's say one batch of 100 grams take only 20 minutes to complete.

The pins that I'm going to be working with do not have any solder or any other visible signs of other materials on them. They're 100% gold plated.

Thanks again for your videos and all the information that I've been learning since being a member here.

Kevin

 

[Geo]

6. H2SO4= Sulfuric Acid = 1 cup 96%+ Sulfuric, 1/8 tsp glycerin (optional). Used as electrolyte in electrolytic cell along with a small amount of glycerin. Effective on medium to large gold plated items. With specially designed anodes and cathodes large batches of smaller plated items can be processed. Not used for Gold filled or karat jewelry.

Use until acid is saturated with black powder typically 12-24 hours of operation. Sink any floating black powder, let settle overnight, pour off bulk of acid for reuse, and dilute remaining acid with 4 parts water

I have my cell setup and ready to start stripping gold plated pins. But I have a few questions I'd like to ask you Steve.

No# 1. I see that the glycerin is optional, but what is the reason for adding it to the Sulfuric Acid?
No# 2. Do the Sulfuric Acid have to be 96%+? or will a lower strength just take longer to deplate the pins?
No# 3. Is the forming of the thick sludge/mud the indication that the solution has been used to its capacity?
No# 4. How many batches should I run after a single batch batch has started, as to not over-heat the charger and the pyrex? Let's say one batch of 100 grams take only 20 minutes to complete.

The pins that I'm going to be working with do not have any solder or any other visible signs of other materials on them. They're 100% gold plated.

Thanks again for your videos and all the information that I've been learning since being a member here.

Kevin

Kevin, i can answer a couple of those for you.glycerin is not needed. it was believed the the glycerin helped precipitate the gold out of solution. this was later found to be a false assumption and that the gold would precipitate out on its own. the sulfuric acid has to be concentrated or it will dissolve base metal which will contaminate your gold. also,dilute sulfuric acid will attack your anode basket.the sulfuric will continue to be effective until it absorbs too much base metal (copper, nickle, and what ever else it will attack).diluting the acid and then evaporating will cause the base metal to precipitate out as sulfides of those metals and then it will be ready to use again.normally, you can use the same solution until it resembles thick brown molasses. the charger should not overheat unless it has a malfunction. keep the amps below 8 amps with a 1 L cell for about a half hour if you are using a basket and then shut down and let the cell cool completely. doing small pieces 1,2,3 pieces at a time should need no shut down or cool down.

 

[Anonymous]

Thanks Geo, you've answered my questions, and thanks for the quick reply too.

This forum is awesome.

Kevin

 

[g_axelsson]

...diluting the acid and then evaporating will cause the base metal to precipitate out as sulfides of those metals and then it will be ready to use again.

Are you sure it is sulfides and not sulfates?

/Göran

 

[Geo]

im not a chemist and most of what ive learned of it has been mostly in the last couple of years. this is what ive learned about sulfides and sulfates.most sulfides are not water soluble while most sulfates are water soluble. the precipitate that occurs when i evaporate my used sulfuric acid from my stripping cell does not seem to dissolve in water. since ive never tested for either and didnt weigh the powder for weight changes, i suppose there could be a combination of both sulfides and sulfates. i cant really argue about it one way or the other but just state what ive seen happen with my material. i am assuming that is what is going on there and its just my opinion.

 

[burningsuntech]

Eureka, Steve. All this in one place. Great job. Thanks! - RA :idea: