# What Should be ideal ph ?



## hrushi (Oct 31, 2009)

I cement Ag using Cu bars.
I add urea to reduce the ph of the solution(AgNO3+CuNOO3+H2O)
But the problem is that not all silver is cemented even after keeping it for more than 12 hrs.
So the remaining Ag I have to precipitate using NaCl.
I dont want AgCl as it increases work to be done and time and efforts.
Case 1
I add less Urea that means when ph is more Cu is dissolved more.
But amount of Ag is less or sometimes Ag is fully recovered.
Case 2
And if I add more Urea then ph is of course less but the amount of Ag remaining in sol is more.
So more AgCl which again has to be cemented 

So What Should be ideal ph ?
Any of time I have not CHECKED ph but now onwards I will Keep record of it
Regards 
Hrushi


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## Harold_V (Oct 31, 2009)

I have no idea why you need urea. I recovered silver from a nitrate solution for years on end, never paying any attention to the pH. I knew it was acidic, and, if fact, tended to perform better if there was a touch of free nitric present. 

One thing you should consider is the fact that when you cement silver, the early cemented silver drags down considerable silver nitrate. It is held captive by the cemented silver and will be liberated only if you give it reason. When your silver has been cemented down, it's always a good idea to use a gloved hand and stir the material vigorously. That will almost always liberate silver nitrate, which will then be cemented on the copper. 

Make sure you have a generous amount of copper present. The greater the surface area, the faster will be the recovery. It would be totally unreasonable for me to find silver still in solution after twelve hours. A full day would provide 100% silver recovery, along with any traces of platinum or palladium that hitched a ride. If you aren't enjoying similar success, I suggest you investigate your procedure. You're doing something very wrong. 

Harold


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## Oz (Oct 31, 2009)

Harold_V said:


> When your silver has been cemented down, it's always a good idea to use a gloved hand and stir the material vigorously



I have on more than one occasion had to appear at a social occasion with the brown dots on the fingernails or black on the skin from silver nitrate without gloves.

I cannot understand the urea either Harold, as it is an inhibitor of nitric. If you are cementing silver on copper in nitric the cementation is not complete IMHO until the nitric solution is saturated with copper. I agree completely with Harold that the surface area of copper exposed to the solution is the key to speed, short of heat (I do not recommend heat for most cementations). 

My hat is off to you Harold as I had never considered the entrapment of silver nitrate solute within the silver cemented. I have not perhaps seen evidence of this when casting anodes as I stir often, but for the purpose of settling for decantation rather than freeing solute.

Given the concern here of leaving silver values behind that have not cemented on copper I should share some of my experience. I probably use less than optimum surface area of copper when cementing silver as I do not use sheet material. I do however let it set for 48 hours (room temp) then decant to get the bulk of values. Afterwards I let the resulting filtrate set with copper present from the initial cementation for an additional 2 weeks. I may get at most an additional gram of additional precipitate per liter. 

When I reduce the volume of this concentrated copper nitrate solution with evaporation to reduce volume I get an additional gram or so that crashes out (at the copper nitrate saturation point) per 4 liters, just shy of the crystallization stage of copper nitrate. It should be noted that these later precipitations are higher in PGMs if they are present in solution.

One last note. When I say a solution is saturated with copper or silver that is entirely dependent on the concentration of nitric available to dissolve these elements.


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## hrushi (Nov 18, 2009)

Harold_V said:


> I have no idea why you need urea. I recovered silver from a nitrate solution for years on end, never paying any attention to the pH. I knew it was acidic, and, if fact, tended to perform better if there was a touch of free nitric present.



I add urea to see that excess free nitric is not present. If there is excess free nitric then it will start dissolving Cu Rods and if so solution will boil out then lot of fuming and dissolving of Cu is also more. I add very less Water. 



> One thing you should consider is the fact that when you cement silver, the early cemented silver drags down considerable silver nitrate. It is held captive by the cemented silver and will be liberated only if you give it reason. When your silver has been cemented down, it's always a good idea to use a gloved hand and stir the material vigorously. That will almost always liberate silver nitrate, which will then be cemented on the copper.



Ya that's really true i have found this many times 



> Make sure you have a generous amount of copper present. The greater the surface area, the faster will be the recovery. It would be totally unreasonable for me to find silver still in solution after twelve hours. A full day would provide 100% silver recovery, along with any traces of platinum or palladium that hitched a ride. If you aren't enjoying similar success, I suggest you investigate your procedure. You're doing something very wrong.
> 
> Harold



This time i added lot of Cu. I almost tripled the quantity of Cu strips and all the Ag was cemented. And time and efforts required were very less.
Thank You


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## butcher (Nov 19, 2009)

the acid will only dissolve enough copper in solution to make copper nitrate if excess nitric was used, and then the copper will only dissolve to replace silver in solution, then reaction will stop, once saturated copper nitrate solution is reached, and silver has precipitated from solution, as long as temperature is not changed.


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## golddie (Dec 13, 2009)

I would like to take Junkmen Jims silver cell as an example.
Would it be ok to add lye to the spent solution and also can I trhrow this spent solution in the drain and what should be the pH befor I throw it away.
Thanks


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## goldsilverpro (Dec 13, 2009)

> I would like to take Junkmen Jims silver cell as an example.
> Would it be ok to add lye to the spent solution and also can I trhrow this spent solution in the drain and what should be the pH befor I throw it away.



Why would you want to throw it away? Depending on the purity of the silver anodes you start with, a lot of silver can be run though it before the copper is so high (about 12 oz/gal) it starts contaminating the silver crystal.

When it reaches this level, the silver remaining in the solution should first be cemented out with copper. At this point, you basically have a copper nitrate solution with a little acid in it. Neutralizing the acid at this point, with lye. you'll end up with a sodium nitrate solution containing a precipitate of copper hydroxide. The copper hydroxide is just as much toxic waste as the copper nitrate was. 4metals, Harold, Steve, and others have written excellent articles on how to properly treat the copper nitrate solution.


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## golddie (Dec 13, 2009)

Hi Chris
Thanks for your rapid reply.
If anyone can give me the link to one of those link that would be a big help.
Thanks


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## butcher (Dec 13, 2009)

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=47&t=1300&p=45405&hilit=dealing+with+waste#p45405

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=47&t=1300&hilit=dealing+with+waste

there are alot more posts, on dealing with waste.

most of mine I reuse one way or another.

any nitrate especially copper nitrate can be used to get some nitric acid from it by distilling with sulfuric and bubbling gas into water then concentrating this solution, then the copper sulfate byproduct can be used in electroplating or for other uses. I think recycle not waste when I use these chemicals.


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## golddie (Dec 13, 2009)

Hi Buthcer
Thanks for your help.

Can you recycle the waste from 4metals post 


> I think recycle not waste when I use these chemicals



Waste treatment for the small refiner
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=47&t=1300&hilit=dealing+with+waste
from this post I mean
Thanks


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## butcher (Dec 13, 2009)

once theses acids and salts have been treated for disposal they would not be too good for reusing.as the acid has been neutralized and metals like copper are removedand lime , cat litter etc, added.
after most metals removed with iron, I do save the metal powders precipitated (copper), and evaporate the neutralized (acid) solution (before any lime is added )(few metals like iron in solution) down to powder and then use this (with iron) to precipitate copper and lower acidity, on my next batche of waste, and repeat that. so by reusing my waste here I save alkali, and reduce bulk considerably ,do not generate so much waste to have to dispose of, if not a person could get overwelmed with the bulk of it, it seems to grow in volume as we treat it for disposal, and it was harder for me to dry it, (aluminum seems to attract water and hang onto it), so I found spending time and money on a hot plate or crock pot is worth not having such a volume of waste. 
alkali (iron)solutions are also good to restore rusted items using electrolisis (a process used to restore antique's)
most acids still have strength and can be used in chemical reactions or can distilled for purer product leaving behind metals.
or they can be reused to disolve base metals in recovery, or great to disolve aluminum, some things like copper nitrate and copper sulfate have many uses, in electrolysis cell chemistry, copper sulfate is sold at wall mart to keep roots of of sewer lines, iron sulfate can be made from copper sulfate and so on.
hope this make sense I dont explain things very good.


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## golddie (Dec 13, 2009)

Hi Butcher
Thanks for your help.
I had been concentration of refining and the scrubbing part of this business and not paying enough attention to reusing and disposing some the wast
I did read Dealing with Waste and thought it was enough but I see that I have to do more reading in this subject
Thanks again


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## golddie (Dec 14, 2009)

Hi Butcher
Thanks for your help
You have some very creative ideas with what to do do with waste



> copper sulfate byproduct can be used in electroplating or for other uses



If I want to make a copper plating solution for plating aluminum 
How would I do that


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## goldsilverpro (Dec 14, 2009)

> If I want to make a copper plating solution for plating aluminum



Plating anything on aluminum is difficult and is definitely not for the beginner. No type of plating will stick to the aluminum without applying an immersion zinc layer first, using a zincate solution. Zincate solutions normally contain cyanide. Also, the best copper plating solutions used for this purpose contain cyanide. A copper solution made from copper sulfate wouldn't adhere. Also, homemade plating solutions of any type are most always inferior to commercial solutions. Workable plating solutions must be prepared using very exacting formulations and must be used with exacting metal preparation cycles. If you are interested in plating, I would suggest you join the large hobbyist plating group at: 
http://tech.groups.yahoo.com/group/Electroplating/

Or, for a more professional group, go to:
http://www.finishing.com/Letters/index.html


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## golddie (Dec 14, 2009)

Hi Chris!
Those are very helpful tips.
Thanks


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## butcher (Dec 15, 2009)

Chris thanks for the information on plating.

aluminum is very reactive to acids and dissolve's with alot of hydrogen gas evolving.


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## goldsilverpro (Dec 15, 2009)

I have some experience in plating, since I was in it for 10 years and owned 2 plating shops. 

Note aluminum's position on the electromotive scale. Right near the top. Just about any metal will immersion plate (same as cement) onto it. Immersion plating usually has very poor adhesion, especially on aluminum. An exception is zinc from an alkaline zincate solution. Actually, to get maximum adhesion, a double zincate is often used. The aluminum is cleaned and put through the zincate. The zinc is dissolved in nitric/HF and put through the zincate again. 

Another problem is that most aluminum is heavily alloyed. Also, if sand castings, there could be as much as 20% silica on the surface of the parts. These alloying ingredients and silica must be considered and the prep cycles are often different for different alloys. In the case of silica, the cycle most always involves fluorides - usually HF.

I know this is probably more info than you wanted. I wrote it to show the complexities involved in plating in general. Everything is exacting and must be done in order. Luckily, most plating knowledge is out in the open and there are many books that tell you exactly how to do it. It's common for those without plating knowledge to think they can take their garbage and make plating solutions out of it. Think again! It's similar to someone with no knowledge of gold refining to think that "they just melt it down."


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