The Brass World

[jimdoc]

Here is The Brass World on The Internet Archive;

http://www.archive.org/search.php?query=platers%20guide

If link stops working just search platers guide.
It has Volumes 5-11. If anybody finds any others please add them here. It looks like lots of info in what I saw so far, and would like to see if the articles Hoke mentions are in there.
Jim

 

[goldsilverpro]

Great find, jimdoc. I downloaded all of them.

I love this sort of thing. When I was a kid, I constantly checked out books like Henley's Formulas from the library. You never know what you'll find. For example, I just found this little gem on page 244 in the #5 volume - Stripping gold from brass or copper.

H2SO4 - 10 parts
HCl - 2 parts
HNO3 - 1 part
Mix the HCl and HNO3 and then pour the H2SO4 into it.

I know that this would be an extremely fumey solution. As a plater, I've used combinations of these 3 acids as bright dips for various metals and they are nasty. I can understand how it would work for gold on copper. I have no exact idea how one could get the gold out of the solution, but it shouldn't be too tough. I assume that lots of dilution would first be required.

 

[qst42know]

Page 217 of volume #5 has a recipe for stripping and recovering silver from silver plate. 8)

Any thoughts on the method?

 

[goldsilverpro]

The silver stripping method is basically one that's been covered several times on the forum. It's a nasty dangerous solution, especially when used hot. Brass World gives 2 methods. If used cold, the formula is 10/1, H2SO4/HNO3. On the forum, I have discussed using 20/1, H2SO4/HNO3, which is today a standard plater's method for removing faulty silver plating from brass or copper. For thick silver, all the plating books tell you to heat it to 180F. That really makes it dangerous. For normal silver plating thickness, it's not necessary to heat it.

The other method they give is used hot. It uses conc. H2SO4 plus pinches of NaNO3 or KNO3. Essentially the same thing as using HNO3.

In both cases, you have to dilute the solution to get the silver. They salt out the silver as AgCl. I suppose you could then evaporate down the solution in order to reuse it. If I did want to reuse it, I would only use enough HCl or NaCl solution to precipitate about 90% of the silver as AgCl. If you used an excess, you would end up with free Cl- in the strip solution, which would be very undesirable.

 

[qst42know]

Wouldn't any free Cl be removed when boiling to re-concentrate the sulfuric?

 

[goldsilverpro]

Wouldn't any free Cl be removed when boiling to re-concentrate the sulfuric?

Were it chlorine gas, Cl2, it would be removed. However, it's not Cl2. It's in there as chloride ion, Cl-, which would not be removed. Apples and oranges.

About the only way you could remove the Cl- would be to add some additional AgNO3 to precipitate it all as AgCl and then filter it. This would be done while the solution is dilute. It's best to not add an excess of Cl- to start with. After diluting, I would analyze the silver in solution with the Volhard method and then add only enough HCl to precipitate about 90% of the silver.

I did this once on a grand scale when I was stripping silver braze from 50,000# of stainless steel in a 50% nitric solution. When the stripping slowed down, I dropped out 90% of the silver as AgCl, with HCl, and reused the nitric for stripping more material.

Theoretically, you could form Cl2 gas from the Cl- by electrolyzing the solution. The Cl2 would come off at the anode. However, I don't think this would work too well in this situation and I think it would take forever and wouldn't remove 100% of the Cl-.

 

[jimdoc]

Here is Henley's formulas if anybody wants to check it out;

http://www.archive.org/details/henleystwentieth00hiscrich

 

[g_axelsson]

I'm no chemist but wouldn't Cl- ions in sulphuric acid behave as hydrochloric acid and evaporate off as HCl gas, leaving NaSO4 behind in the solution?
Just as we could make our own nitric acid from nitrates in H2SO4 and distill.

After a quick search I found this process http://en.wikipedia.org/wiki/Mannheim_process but I couldn't find which temperature is used to remove the HCl gas from the H2SO4 + Na2SO4 mixture.

/Göran

 

[qst42know]

It's in the google books link at the bottom of the Wiki.

From the book, at a temperature of 840c.

I won't be trying that process. :shock: :lol:

 

[Lou]

g_axelsson: Yes, you are in fact correct--because of sulfuric acid's low volatility, any free chloride present would be converted to HCl gas, this works less well for bromide, and not at all for iodide (which simply ends up as iodine).



Lou

 

[goldsilverpro]

Lou, you are right, of course. For certain types of parts that wouldn't strip normally, I used to add a small percentage of HCl to the sulfuric stripper. The first day, or so, it fumed like crazy - chlorine gas. However, the added stripping ability on these oddball parts lasted for quite a few days, maybe a month. I sort of feel it was not Cl2, but Cl-, that was aiding the stripping. I don't think all of the Cl- was eliminated. Of course, I wasn't heating it.

 

[jimdoc]

Here is one for you guys thinking about recovering your copper;

Preliminary evaluation of copper, nickel, and chromium recovery from wastes generated by the metal finishing industry in Ontario (1991)

http://www.archive.org/details/preliminaryevalu00pyneuoft