# Testing acid PH.



## firedan525 (May 1, 2007)

Hello everyone. I have been reading many of the past blogs and a question arose. First using sodium nitrate w/ HCL for my AR it is very hard to keep free nitric low. So when I'm done dissolving I've learned that it is important to make sure PH is 1 before percipitating gold. I have looked around the web and have found electronic PH meters to be very expensive, so I have bought acid test strips. I sould have asked before ordering but they were rather inexpensive and I want to do this right. After the first couple successful batches and my confidence boosted I may start trying other things. Another question is sodium nitrate & HCL Aqua Regia acceptable to acheive quality 99+ gold purity and what precautions can I take using this AR formula to lessen the liklyhood of contaminants.
Thanks alot. DAN


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## goldsilverpro (May 1, 2007)

If you buy the right kind, pH paper or strips work fine for this purpose. The most common and the cheapest is the pHydrion brand. It comes in rolls in a Scotch tape type dispenser. The entire range of pH is from 0 to 14. The pHydrion paper comes in narrower ranges than this. The most common is universal paper, which usually goes from 1 to 12. This is not suitable for you because you can't see the color change difference in going from zero (strong acid) to 1. Try to find paper that starts at zero or .1. The pHydrion brand come in a wide assortment of ranges. The prices all run about the same - cheap.

A perennial high school lab experiment is to make your own pH strips from red cabbage juice. Google it. I don't know if these are sensitive enough to get into the 0 to 1 range, however.

Always having nitric acid, I have never had a need to use the sodium nitrate/HCl mix. I would imagine the basic rules would be the same as real aqua regia - good filtering, etc. Who knows, with very good habits, you might achieve 99.95 purity.


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## firedan525 (May 1, 2007)

Thanks alot i really appreciate the amount of help i get using this forum. It is a great thing. I think, no i know i have alot to learn from you all.


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## catfish (May 1, 2007)

Hi Dan:

I have a ph tester that is fairly accurate. It cost ~$25.00, (about 1.2 grams of gold) which I consider very inexpensive. It is digital readout. It has an accuracy of + or - .1 ph.

I always reduce (neutralize) the nitric acid in my spent AR to somewhere around .1 to 1.0 ph (1.0ph is best) before I add the percipitant. I think this is probally one of the most important steps in refining. I do this with disolved Urea in hot water, for it is faster acting. You never wind up with any undisolved urea in your solution. You can figure how to determine the amount of H2O to disolve the urea. Or PM me and I can tell you.

As far as the meter, should you get one, be sure and order the 4.0PH acid calibration solution. by calibrating the meter with this near acidity level, you improve your tolorance by about 90+ % in the low levels that you will be reading. 

As far as the pureness of your gold, I am not sure just how much, if any, the level of Nitric acid at this point of the process effects the pureness. The level of nitric effects the precipitation amounts more than any thing. (like no gold to maximun gold output from the AR). Try never to leave the table untill you get it all. Invest in a bottle of precious metal testing solution, it can pay for itself on one poor precipitation.

Any gold that you refine and sucessifully recover from the AR, then the processes begin on just how fine or pure you want to make it. If you want to be a MASTER refiner, then you should take all the reccomended steps and make .999 near pure gold. I am not a master refiner and stop at .995 to .998. I sell all my recovered and refined gold. There are a couple of folks, Harold, Steve and Cris, that can stir you in the right direction on how to do this.

The ph meter is manufactured by Hanna Instruments. You can buy them on ebay for about ~$25.00 plus ~$7.00 for the 4.0 calibration fluid.

Lots of luck.

Catfish


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## lazersteve (May 1, 2007)

I have one of the same brand Catfish Mentions.


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## goldsilverpro (May 1, 2007)

Good post, Tom. I didn't know that pH meters had gotten that cheap. I found the seller on eBay. Do you do a 2 point calibration with both the 4 and 7 buffers? I also noticed he sells a 1.68 pH buffer but, it costs $10. I wonder, though, if that might put you closer to your work? I'm sure the 4 is fine. This isn't rocket science. Somewhere, I have some formulas for making all the various buffers. I'll try to dig them out.


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## catfish (May 1, 2007)

Goldsilverpro:

Yes, I do a 2 point calibration 4.0 and 7.01. The meter has two calibration settings. I found that the most important one is the 4.0. When I first got my meter I was not aware that the meter should be calibrated at 4.0 too. I found out by trial and error. Once I got some 4.0 calibration fluid, I found my test results much improved at the lower end of the scale.

This is another great thing about this forum, is the vast amount of experience and knowledge that is so easy to access. when I started, I did not know anything and learned the hard way.


Catfish


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## tom341 (May 12, 2007)

WOW I just bought one of those Hanna PH meters from E-bay two days ago, and it makes me feel good that I did something right. I did not know about the 4.0 calibration fluid though, but I ordered some for about $18.00 for 10 packs of the 4.0 calibration fluid. “that’s s/h and all”. <*\\\><..TOM  8)


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## AuMINIMayhem (May 12, 2007)

catfish said:


> I have a ph tester that is fairly accurate. It cost ~$25.00, *(about 1.2 grams of gold)* which I consider very inexpensive.



now that's what I call "gold fever".. Catfish, I don't know why, but that was funny as hell! You're alright, man! I like the way you think!  8) 

Derek


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## lazersteve (May 12, 2007)

Everything is measured against the value of gold it seems! 

When people ask me why I don't sell my gold for money, I tell them it's because the dollar is only going to decrease in value over time whereas the value of gold will likely increase over time. :wink: 

Steve


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