HCl + NaNO3 =....

[Duster]

Hey guys, new here. If you couldnt guess, I'm a little new at this, and normally I lurk around for a while until I get some knowledge under my belt but I just have to ask this question...

So I saw the book on scribd that was linked to from here and thats where I got the idea for the poor mans AR using HCl and sodium nitrate instead of nitric acid, since thats a little pricey for me. Anyway the amounts listed said it was good for 160g of pins, well I have (had) about 70, so I halved the amount. I'll walk you through what I did and you can tell me what I did wrong, or where I messed up...

4 ounces of NaNO3 was added to 240ml of water, as much was dissolved as possible. A shallow layer of remaining sodium nitrate was left, but not much.

480ml of HCl (the store bought 31% or so grade) was added next. Vigorous stirring ensued only to find a THICKER layer of a white precipitate at the bottom.

Perhaps jumping the gun at this point, I heated it in a hot water bath and added all 71grams of pins. At first little to nothing was happening then it began to fizz... Some more stirring, more fizzing. Eventually I took it off the hot water bath. More fizzing... Moved the beaker outside. LOTS of fizzing and foaming and overflow and it was green (initially the solution was clear, adding the pins made it yellow, then it turned green).

Noticing the telltale red/brown NOx cloud I promptly left (after a bit of a sting to the nose at that... sure hope in 2 weeks I'm still here).

Eventually the reaction subsided, the beaker was very hot. A lot of foam overflowed (no doubt losing a lot of gold). Once the fizzing all but stopped (there was a little left) I took a closer look and could see gold flakes floating around, albeit not much (I figured).

At this point I figure the reaction/test in junk. I mean, yeah there is gold and Im going to save it but I have no doubt my yield will be *crud*. I am in the processing of neutralizing with urea. The solution is very very dark, cant even see through it. The remaining few bubbles and what not still come up green.

What I dont get, is why the bits of gold didnt react and dissolve, unless its only suppose to react with the base metal? I was under the impression it would dissolve the gold though.

And furthermore, is there any gold in solution? I figure there is some, but how much I don't know.

Im sure neutralizing will take a while, so any suggestions from here?

 

[Harold_V]

My advice to you is the same as it is for others. Read Hoke. It won't instantly solve the riddle you face, but you'll come to understand some of the important steps in processing gold---one of which is to limit base metals before attempting to dissolve values. I can go on, but until you have a better understanding, it's not going to do you much good. Just be content to know that if you dissolve values in the presence of base metals, and they are not fully consumed before the free acid is consumed, some, if not all, of the gold will be cemented, and it may or may not look like gold.

Read Hoke. Learn how to eliminate base metals. Consider not using urea.

Welcome to the forum!

Harold

 

[martyn111]

Noticing the telltale red/brown NOx cloud I promptly left (after a bit of a sting to the nose at that... sure hope in 2 weeks I'm still here).

Being new is no defence against the chemicals, wear appropriate safety equipment.

 

[Duster]

Thank you for the tips and I will look into Hoke. I have seen him mentioned a lot around here, though I never really knew exactly where to find his book. I'll do some searches though.

Far as safety equipment goes, I don't have a fume hood or respirator, but it was done outside, and all other safety precautions were followed (gloves, clothing, eyes, hose, etc etc). Way back in the day I had a bit of a run in with some nasty chemicals and a prompt visit to the ER, not something I really feel like repeating...

 

[jimdoc]

Thank you for the tips and I will look into Hoke. I have seen him mentioned a lot around here, though I never really knew exactly where to find his book. I'll do some searches though.

Hoke was a she, and a link to her book is in Palladium's signature line;
http://goldrefiningforum.com/phpBB3/memberlist.php?mode=viewprofile&u=1666

Jim

 

[Anders Hoveland]

In a mixture of muriatic acid and sodium nitrate, there is a very small equilibrium:
(2)NaNO3 + (4)HCl <==> (2)NaCl + (2)H2O + Cl2 + NO2 + NO

Theoretically, if the reaction could be made much more acidic, the equilibrium would shift more to the right. The reaction would not really be driven much towards the right until acid concentrations of around 70%, which is not possible for muriatic acid, since only so much HCl (which is a gas in the pure form) can dissolve in water.

One would wonder whether the sodium nitrate in the concentrated muriatic acid solution could act as a catalyst, allowing some of the hydrochloric acid to be oxidized by the air:
(4)HCl + O2 <==> + H2O + Cl2 ?

(since the oxides of nitrogen would react with oxygen to form nitric acid)

Does anyone know what is happening in this reaction?

It is known that mixtures of nitric oxide and nitrogen dioxide together can attack ammonium salts. Perhaps letting a little ammonium nitrate dissolved in hydrochloric acid (32%conc) sit around for 24 hours will answer the question. If there is indeed any equilibrium, a portion of the ammonium nitrate should react, with the net equation:

(3)NH4NO3 + (6)HCl --> (9)H2O + (3)N2 + (3)Cl2

will do experiment and let everyone know how it went. If there is no reaction, than it would strongly suggest that there is no chlorine or nitrogen oxides in equilibrium.

(typically NCl3 will not form under strongly acidic conditions, but one should still be careful)

 

[element47]

if you dissolve values in the presence of base metals, and they are not fully consumed before the free acid is consumed, some, if not all, of the gold will be cemented, and it may or may not look like gold.

As usual, Harold comes up with the remarkably cogent means of expressing an important thought. Thanks, Harold!

 

[Geo]

there's a couple of things i might be able to add to this.heating a solution to speed up a reaction before understanding what will happen is a bad thing as some of the chemicals mentioned here and the very ones you were using are ingredients for making highly explosive compounds.speed doesn't necessarily win the race every time.take things slowly until your very sure the outcome will be at least close to what you expect.the process you tried would have worked just fine if left at ambient temps,and always use a reaction vessel large enough to hold the reaction in the case a runaway reaction occurs like this time.did you have your vessel in a collection pan? always put gold bearing solutions in a collection pan in case of glass failure or runaway reaction,even when storing.tupperware works great.

 

[p13t_chan]

Learn how to eliminate base metals. Consider not using urea.

Harold

Why did you suggest him to consider not using urea.cause i do it too for my process.What the effect if not using urea?

 

[Harold_V]

Learn how to eliminate base metals. Consider not using urea.

Harold

Why did you suggest him to consider not using urea.cause i do it too for my process.What the effect if not using urea?

There's no shortage of guys that endorse its use. I don't, and I never used it in practice in my more than 20 years of refining. It's not necessary, and can lead to bad habits, in particular, wasting nitric.

I've made no secret of the fact that I am not a chemist. However, there's a faction of readers that have expressed the concept that urea can interfere with the recovery of the platinum metals. In any case, why use another chemical when it can be avoided?

When it's all rendered down, it's a little like how you like to eat your pancakes. Some folks like them with syrup. Some may prefer mustard.

Harold