# Reflux Condenser for hot Aqua Regia?



## 924T (May 3, 2014)

Greetings, all!

When boiling substances in Aqua Regia, would using a Reflux Condenser and running iced water through it
cause the AR fumes to actually condense and trickle back into the boiling vessel?

I just bought a Tsunami 800gph submersible pump for use with a miller table or a sluice or a wave table,
and the thought hit me that there is no reason that I can see why one couldn't use it to pump iced H2O
through a reflux condenser (in a recirculating system), so I thought I'd get some opinions on whether or
not that would work with AR fumes.

If it would work, then there would be fewer fumes to be scrubbed.

Cheers,

Mike


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## Irons (May 3, 2014)

Reflux is the way to go. A bit of air flow, or, even better, O2 to convert NO into NO2. You can add Peroxide, but it will dilute your AR over time, which may not be a good thing. It will just take more time to digest. Look into using Bromine with Nitric instead. It condenses quicker and will afford less loss to the exhaust. Harold can comment on the effectiveness of Br2 and Nitric.

A quick and easy method of producing O2 is Manganese Dioxide and H2O2. The MnO2 just acts as a catalyst to break down the Peroxide into O2 and Water. A cheap source of MnO2 is a carbon-Zinc Battery. The black powder between the Carbon + electrode and the Zinc case is Manganese Dioxide saturated with Ammonium Chloride. All of them useful items. The only warning is to not drip Concentrated H2O2 directly onto the MnO2. It can get pretty violent. I just use a small amount of MnO2 mixed with H2O and slowly drip the H2O2 to get the flow of O2 that I need. It's great stuff to inject into the Furnace to get the Temperature up in a hurry. No toxic waste and you just need to turn off the H2O2 drip when you're done for the Day. :mrgreen:


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## 924T (May 6, 2014)

Irons,

Thanks for weighing in on this!

I had to hit Wikipedia to get a little smarter about batteries, but I now know that the Alkaline version is not
the way to go for this (however they might be a source of KOH, if it could be extracted, because the Potassium
Hydroxide apparently does not get consumed as the battery is used).

The Carbon rods from the Carbon-Zinc batteries could be used to make a small Carbon arc furnace, methinks.

Regarding generating Oxygen with H2O2/H2O and Manganese Dioxide, would the Oxygen be directed into the 
boiling flask, or after the Reflux Condenser? If it's into the boiling flask, then I need to be looking at 2-neck
flasks.

The longest Reflux Condenser I've found so far is 500mm----I'm assuming the taller the cooling stack, the better.

Also, I've found bargain Reflux Condensers in the $70-80 range, and brand name Condensers in the $200-300 range.

Is there a quality or durability advantage to paying triple the money to get a brand name Reflux Condenser?

Cheers,

Mike


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## Irons (May 6, 2014)

Hi Mike,
The price of multi-neck flasks really rises compared to a single-neck flask. Just use a Claisen adapter to give you the extra inlet you need for the O2.I picked up a 9 bulb, 900mm Allihn Condenser on fleabay for less than 50 bucks a while back. The top of the condenser should have a ground fitting for a hose adapter for your outlet. You will need another hose adapter for your O2 inlet. Since we're dealing with Nitrogen Monoxide Gas, the location isn't that big of a deal. Stick with Pyrex or Kimax. There are other good brands out there, but don't buy the cheap Chinese or Indian crap. Personally, I like Kimax. They use thicker glass.


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## 924T (May 13, 2014)

Irons,

I've been busy researching/pricing glassware, and that 900mm Condenser you got must really be a rare
bird----------I couldn't find one anywhere, much less pictures of one of those.

I very much appreciate your advice-----I'm going to stick with Kimax as much as I possibly can. I ordered in
2 400mm Kimax bulb condensers last night, with 24/40 joints.

It turns out that I don't have any Carbon-Zinc lantern batteries around here, so I'll have to go looking for
some dead ones.

I did see where Menard's sells Propane-torch-size tanks of Oxygen, which might be able to fill the gap
between now and when I get some Carbon-Zinc batteries------------since only a trickle of O2 is needed
to neutralize the Nitric fumes, wouldn't it be possible to put a regulator/valve/nipple on a small Oxygen tank
like that, and run rubber tubing to the boiling flask/Claisen adapter/stem adapter, to get the job done?

You've given me the antidote to my wife's objections to having/using Nitric Acid at my house (outside, of course),
so this is starting to become fun.

Many thanks,

Cheers,

Mike


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## Irons (May 13, 2014)

The Oxygen converts the Nitrogen Monoxide (invisible) to Nitrogen Dioxide (red fumes), which combines with Water Vapor to produce Nitric Acid, so you still have Nitric fumes to deal with. I think you will find Carbon-Zinc batteries listed as 'Heavy Duty'. They are cheap and easy to find. The Oxygen Cylinders you describe will work, but the Hydrogen Peroxide method will be less expensive in the long-run. The Manganese Dioxide will last a long time, since it is a Catalyst and remains intact. Most of the loss will be from pouring out the excess Water, since it has a very fine particle size and tends to stay in suspension.


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## 924T (May 14, 2014)

Thanks yet again, Irons!

Would my original idea of running ice water through the condensers cause too much of a thermal differential
for the Pyrex to handle (considering that the Aqua Regia would be boiling, so the vapors heading in to the
condenser(s) would be over 200F?

Cheers,

Mike


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## Irons (May 14, 2014)

The usual procedure is to input the cold Water from the hot end of the reflux column, but I prefer to feed the cold Water into the top of the column, thus giving a gradual temperature change. You can monitor the temperature of the outlet and adjust your Water flow accordingly.

Start out by refluxing Water to get the feel of how things work, and only fill your flask half-full, at most.


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## necromancer (May 14, 2014)

awesome thread !!!!!

for temperature readings take a look at one of these (thanks to GSP)

http://www.miniinthebox.com/digital...ser-sight-50-c-380-c-58-f-716-f-_p200934.html


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## justinhcase (May 14, 2014)

Yet again Thank you Irons!!!!
Very helpful and well put.
Much thanks.


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## Lou (Jun 6, 2014)

Even ice cold water will not stop NOx and condense it (takes LN2 to freeze the stuff). What'll probably happen is it'll allow some of it to redissolve into the nitric, HCl, or whatever is refluxing in the condenser.

You won't find that thermometer useful for transparent glass--it works based off of an adjustable emissivity coefficient, different for varying materials. 

Just get a 76 mm immersion spirit filled thermometer. The Pyrex will handle a 200 F temp differential with no problem, just be sure it's truly borosilicate.

A good source for glassware is pleinc.com

or run to your local university surplus and see what you can score (if you can anymore, now with all the people up to no good and liability concerns).



Don't seal the system. If you are really concerned about reagent economy and scrubbing gas (good for you), you might consider bubbling the NOx through peroxide--be warned, any HCl going through will decompose it.

How it's done is: sand bath (or steam bath if you're so lucky) heated resistively with the flask nestled in that; else use a Glas-col mantle, then fill your flask no more than half way and never heat on full power, then on the top of the flask connect your condenser, keck clamp it, secure in a three prong to your ring stand or lattice, then on top of the condenser connect a 24/40 to barbed glass fitting, connect good chemical resistant tubing to it and to a couple gas washers filled with sodium sulfite/2 M NaOH. Done right, the produced gas will never need to go through more than a few inches of water and you ought not to see any precipitate in the wash bottles. You should have one empty one to catch any suck back. 

gas washing bottle:
http://www.ebay.com/itm/like/291158795581?lpid=82
vac takeoff adapter:
http://www.sigmaaldrich.com/catalog/product/aldrich/z137057?lang=en&region=US


Good job trying to be responsible.


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## 924T (Jun 11, 2014)

Lou,

Many thanks!

I will investigate the gas washers immediately, because I really do want to keep my process emissions 
as close to zero as is economically feasible.

Cheers,

Mike


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## Tub Buster (Jun 17, 2014)

Irons said:


> A quick and easy method of producing O2 is Manganese Dioxide and H2O2. The MnO2 just acts as a catalyst to break down the Peroxide into O2 and Water. A cheap source of MnO2 is a carbon-Zinc Battery...


You can buy Managanese dioxide in bulk at a pottery supply store.

One reason to buy it in bulk is that it can be used with phosphoric acid to rust-proof your tools by the parkerizing process. Degrease the tools, then mix MnO2, phosphoric acid and some water, heat to 60 deg Celsius / 140 deg F. and after 10 minutes of so you have a coating that will be very difficult to oxidize.

The "stainless" steel Estwing hammer in the photo below got in the way of some acid fumes. After parkerizing I wiped on a bit of lanolin, wiped it off, and sealed what remained on the hammer with a butane torch.


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## 924T (Jul 1, 2014)

Tub Buster,

Hey, nice job of Parkerizing on your hammer!

I had never heard of Parkerizing until I was researching the history of WWII Thompson submachine guns
a few years ago.

It was really cool to see someone has done it in a home lab.

Cheers,

Mike


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## 924T (Jul 1, 2014)

Irons & Lou,

I'm on it, but it's taking a bit of time to get all the pieces to the glassware puzzle together.

I've got 5 gas washers on the way, 2 Kimble 500ml, and 3 Bel-Art polyporylene 125ml.

2 new 24" ring stands just showed up today; I'm negotiating on some used clamps and 90 degree 24/40
adapters (with hose barb), so it will be at least another week before those get here.

I got the Bel-Art polypropylene gas washers for running the NaOH 'washing' solution, because I
have read while researching glass frit (and the glass gas washers I've got coming both have a 
glass frit diffuser at the end of the gas input tube) that concentrated NaOH will destroy the frit.

Lou, you mentioned using 2M NaOH solution-----I'm going to have to re-learn moles (that didn't
stick from 40 years ago)------a 2 mole solution sounds fairly concentrated, which according to what
I read, would destroy glass frit (what I read was at a manufacturer's website that makes glass frit 
'air stones'------unfortunately, I didn't bookmark it, so I'll have to do some searching if you want to
read what they have to say).

Cheers,

Mike


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## justinhcase (Aug 15, 2014)

Re-Fresh
Sorry his name is Irons,I always add unnecessary punctuation by accident.


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## Harold_V (Aug 16, 2014)

Irons said:


> Harold can comment on the effectiveness of Br2 and Nitric.


Sorry to be late in responding. I was not checking the board when this comment was posted, and I just happened to find it.

Unfortunately, my experience with bromine revolved around cyanide, not nitric, so I can't really lend anything of substance to the point at hand. However, what it does when using cyanide is difficult to believe, as the difference, for me, was profound. 

The gold ore I processed turned out to be a complex. After much reading, I determined it must be a "mispickel ore". For that, bromine was recommended (an old book on processing, milling and smelting. No, I do not recall the title, but it may have been Rose's The Metallurgy of Gold). 

I had exposed the ore to cyanide for several hours ---how many I do not recall, but more than a day. I recovered just a small ball of gold for my efforts, and had the tail assayed to see if I had removed much. Turns out the tail assay was higher than the head assay (the ore ran over 300 ounces/ton, so that was easily accomplished by my less than acceptable taking of the samples in both cases). 

Fast forward to the day when I started the recovery process, using my agitation tank. I introduced only a couple fluid ounces of bromine to the tank, which held 20 gallons of slurry. The response was virtually instantaneous. It was clear that my free cyanide was dropping at an amazing rate, which indicated that it was now dissolving the values. In the end, I recall that I achieved a 99.55% recovery. Couldn't have done it without the bromine. 

Harold


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## Irons (Aug 16, 2014)

Thanks for clearing that up, Harold. 8)

https://en.wikipedia.org/wiki/Arsenopyrite


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