# Sodium Hydroxide



## Moo (Jul 14, 2012)

What strenghth must this chemical be made to for scrubbing noxx gas?


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## NobleMetalWorks (Jul 14, 2012)

When you scrub NOx gas, what you are really doing is putting the gas into the water you are scrubbing with. It can turn into a very weak nitric acid. That is what you are trying to neutralize. Until you do it will be acidic.

You can use different types of substrate, and things like urea to neutralize the nitric. You might want to do a forum search for fume scrubbers.

Scott


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## Moo (Jul 14, 2012)

Thanks the solution I chose to bubble through will be NaoH but how concentrated can you make it without risking glass breakage?


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## NobleMetalWorks (Jul 14, 2012)

Moo said:


> Thanks the solution I chose to bubble through will be NaoH but how concentrated can you make it without risking glass breakage?



If the solution gets hot, or is hot, the glass might not stand up to Lye, that's what you will be making is Lye.

Also, you need a way to measure the PH in the solution, then you make small additions of Sodium Hydroxide to neutralize, then test the PH level again. I add base as needed, and only do so through observing the PH level. I can keep it within the range I want because I have been working with it for several months now. Experience will guide you. But if you are using glass be careful, when you add sodium hydroxide to water, you create a liberal amount of heat. This could cause you problems if you put it directly into glass. I would suggest making up a solution of lye and keep it on hand in a plastic container that can hold it. Then make small additions of the concentrated solution as needed to balance your PH.

Take all the normal safety procedures, Lye is some nasty stuff. Specially gloves for your hands, and eye protection. You have to make sure you do it in a container that can sustain the heat generated, no cheap plastic or glass. You should label it and keep it at floor level or close if possible so you cannot drop and spill it, preferably in a cool cabinet or something similar. I wear an acid bib when I mess around with Lye, and long sleeves. It's very bad stuff.

Scott


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## Moo (Jul 14, 2012)

Thanks Scott I have ph paper here so will come in handy currently I have a borosilicate setup for processing a small batch (8 pentium pros) in AR,
the sachet I have is 70% for such a small batch do you think that sachet in a half litre of water would be suffucient? Or perhaps just run the tubing into a big bucket of water?


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## Palladium (Jul 14, 2012)

I use a 20% solution of NaOh. That's 20g NaHo mixed with 100 ml of water or 200g per liter of water.


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## Palladium (Jul 14, 2012)

You can also use limestone rock and water.


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## goldsilverpro (Jul 14, 2012)

Just be aware that sodium hydroxide solution will etch glass. The stronger it is, the greater the rate of etching.


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## Palladium (Jul 14, 2012)

I ruined a good flask using concentrated Naoh. I like the limestone and water route. 2- 4ft sections of 3in pvc pipe with screw caps on each end for clean out filled with water and limestone rocks with a touch of NaOh added at first.


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## Moo (Jul 14, 2012)

Palladium said:


> I use a 20% solution of NaOh. That's 20g NaHo mixed with 100 ml of water or 200g per liter of water.



My sachet says its 70% NaOh and I am hopeless with math 
Also how will noxx fumes fare against PVC tape? I have a flask with rubber stopper covered it in pvc tape. No chance of explosion?


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## Palladium (Jul 14, 2012)

If its 70% then you would need 30% more to equal the same 100%. The 20g per 100ml is based on 100% NaOh. So 20g times .30 or 30% = an extra 6g per 100ml of solution. So you would mix 26g of 70% NaOh to get the same result as 20g of 100% NaOh.


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## FrugalRefiner (Jul 14, 2012)

I agree with the limestone method. It serves double duty. 

I will use gravel from my driveway - what is known around here as 1" crusher run limestone. I will sift some through large wire mesh, then rinse the large pieces to remove the fines. I can load my scrubber column with the large, rinsed gravel. It provides a large amount of surface area for the gas to pass through slowly. 

It eliminates the need for a separate packing material as well as any exposure to harmful lye solution. All I need to do is wet the gravel down before a run.

Dave


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## Palladium (Jul 14, 2012)

.

You mean you covered it in teflon tape for plumbing? PTFE http://www.watergarden.org/s.nl/it.A/id.777/.f?partner=froogle 
Should be fine. Rubber will break down over time. Can't think of any explosion hazards.


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## Moo (Jul 14, 2012)

No not teflon pvc electrical tape. http://www.supercheapauto.com.au/online-store/products/SCA-PVC-TAPE-10m-Assorted-Colours-10pce.aspx?pid=213265&utm_source=shop_search&utm_medium=search_results&utm_campaign=g_shopping#Description


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## Palladium (Jul 14, 2012)

It should stand up for a minute, not sure. It's not made from the same type of material as pvc pipe is just because it says pvc. It has rubber and plasticizers added to make it stretchable which will break down under expose to Noxx faster.


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## Moo (Jul 14, 2012)

Okay palladium thanks will get teflon. As for the etching properties of NaOh at 20% how long would it take to eat through a borosilicate graduated cylinder?


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## Geo (Jul 14, 2012)

Moo, any strong base will work. sodium bicarbonate comes to mind. you can dissolve as much baking soda (not baking powder) in as much water as you need. it will do just as good a job. unless you are doing refining on a commercial basis, it should do fine. if you suspect your solution is saturated, you can check the PH. if it approaches neutral,change the solution out.


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## butcher (Jul 14, 2012)

You could add a few drops of pH indicator into your scrubber solution the liquid would then indicate pH by its color, then a quick look at solution color could also indicate if scrubber will still be effective at removing more acids from gases bubbled into the solution, or if you need to add more caustic to revive it or change solution.

Also consider what material or gas your using the scrubber for,you may be able to use it to generate a product you can reuse, example if only for NOx fumes I would consider making potassium nitrate (KOH as base), or sodium nitrate (NaOH as base), or just make dilute nitric acid to evaporate and reuse, and then I could reuse the product of the scrubber and not just treat it as waste.


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## Moo (Jul 18, 2012)

thanks for the great tips think ill use sodium carbonate. just as effective as bicarb?


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## Geo (Jul 18, 2012)

yes.


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## Moo (Jul 18, 2012)

Thanks Geo  added a heck of a lot more then water can dissolve


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