# Pvs,Plastic,Teflon



## Refiner232121 (Feb 9, 2010)

I am guessing that nitric acid ,sulfuric acid,AR cant harm Pvs,Teflon.

Will these acids eat away plastic ,or are all 3 the same


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## chemist (Feb 9, 2010)

Sulfuric acid is normally sold in plastic polyethylene bottles.
Neither sulfuric nor nitric will bother Teflon.


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## goldnugget77 (Feb 9, 2010)

I am not sure but all 3 are OK for gold refining


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## 4metals (Feb 9, 2010)

Nitric acid and aqua regia will take their toll on all PVC and Polypropylene. Teflon's OK but expensive. If you are looking for a material of construction for refining in the plastics get brittle over time and eventually crack, much like if you leave it out in the sun for a long time. I've used plastic buckets for acid refining for ever. Just get in the habit of squeezing the pail before you use it, if it's stiff and cracks or doesn't flex like a new pail, consider replacing it.

For storing nitric, stainless steel or glass.

If you do use 5 gallon pails, cut off the handles. If the handles are there we use them, it's human nature, but they are metal and in the acid environment they corrode and break at the most inopportune moments. To be safe I always cut them off.


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## Oz (Feb 10, 2010)

Wise advice on the handles.


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## aflacglobal (Feb 10, 2010)

I looked at my 5 gallon buckets which are about 3 month old yesterday and observed the same thing. Having been in commercial coating in the past i have emptied many a many a many 5 gallon buckets. I couldn't tell you how many times i have pick a new bucket up only to have the handle come off in my hands. Think about 5 gallons of ap in your lap. :shock: 

I thought about taking the handles out and using polypropylene rope instead. I used many a bucket held with rope that did better that handles and it won't rust.


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## overdriv (Aug 31, 2010)

Could someone please comment on ABS (PVC), Nylon, Polyethylene and the reaction that brown fumes from AR would cause to them. I am building a scrubber and have bought Polyethylene tubing for the second, third, and fourth stage of the scrubber, but can only find nylon fittings nibs and nuts and ABS, PVC fittings for the tubing hook ups. (I have PTFE 1" tubing for the first stage of the scrubber, from the lab hood to the first chamber of spraying weak lye onto crushed marble rocks). My assumption is that the NOX (brown fumes) would be neutralized 80% by the first stage and then a second 80% going through a second stage of lye spray over crushed marble.

Also could someone comment on using a vacuum pump being used to suck the brown fumes through the process. Since this is a oil based vacuum pump I am worried about any reaction that might happen with the oil in the pump and the residual fumes.

By the way this is an awesome forum.


overdriv


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## Harold_V (Sep 1, 2010)

overdriv said:


> By the way this is an awesome forum.
> 
> 
> overdriv


Thank you, and, yes, it is! 
We've worked hard at keeping the riff-raff to a minimum, and have insisted on adult behavior on behalf of the participants. It appears to be paying huge dividends. 

Harold


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## qst42know (Sep 1, 2010)

Nylon is a poor choice for acids and it's susceptible to chlorine compounds.


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## overdriv (Sep 1, 2010)

qst42know said:


> Nylon is a poor choice for acids and it's susceptible to chlorine compounds.



Thank you very much for your reply, what would be a better replacement for the nylon fittings PVC? I do not think they make teflon fittings. I think that my choices are for this type of fitting is either Polyethylene, Polyvinylidene (Kynar), or Polypropylene. Which do you think is the best for the scrubber?


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## qst42know (Sep 1, 2010)

Polypropylene would fit my budget better. :lol: 

Teflon would be far more expensive but would likely outlast the both of us. :mrgreen:


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## Irons (Sep 1, 2010)

overdriv said:


> qst42know said:
> 
> 
> > Nylon is a poor choice for acids and it's susceptible to chlorine compounds.
> ...



Teflon fittings are very expensive. Even on Fleabay, they can be several tens of dollars. I was lucky to pick up a lot of fittings at a reasonable price.

I priced some 2 liter Nalgene Teflon bottles and they were over $300 US. Picked up some used ones that looked new on Fleabay for a fraction of that.

Teflon Is the way to go if you can afford it. I like it better than glass, if only for the safety factor.


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## overdriv (Sep 1, 2010)

qst42know said:


> Polypropylene would fit my budget better. :lol:
> 
> Teflon would be far more expensive but would likely outlast the both of us. :mrgreen:



Thank you for your reply, it is not too late for me switch out to Polypropylene. I want to thank all of you for being so kind as to respond and so quickly. I have been on other forums where it takes forever for a response. I will be also good and respond quick and be helpful.


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## Irons (Sep 1, 2010)

overdriv said:


> qst42know said:
> 
> 
> > Polypropylene would fit my budget better. :lol:
> ...



You think that was fast, just try and pull the wool over on someone here and see how quickly one gets their butt handed to them. :mrgreen:


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## nickvc (Sep 1, 2010)

Irons said:


> overdriv said:
> 
> 
> > qst42know said:
> ...


So true , but sometimes necessary to maintain standards and accuracy , the reason we all visit and keep coming back.


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## overdriv (Sep 1, 2010)

I have found 1" teflon nib type fittings costing about $17. each for the PTFE tube that I am buying today . I have breathed in some NOX on the first attempt of using AR and that I hope will be my last (I have already lived past the two week mark.) I like AR because of the efficiency of the process. The electrical Shor method was problematic for me.


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## Irons (Sep 1, 2010)

qst42know said:


> Nylon is a poor choice for acids and it's susceptible to chlorine compounds.



Nylon is good for alkaline solutions.


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## overdriv (Sep 1, 2010)

Thanks Irons:

I will use them when I have to upgrade my scrubber if I have too. What do you think about using the bedliner paint to make/paint the inside of a fume hood? Will this react with the NOX or is it though enough for the fume hood / lab hood/ scrubber hood -stage one.


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## Lou (Sep 1, 2010)

Polypropylene is quite resistant to acids as is HDPE. The higher the molecular weight, the better. You can buy fluorinated PP or HDPE for a fraction of the price of fluoropolymers. 

Teflon is super expensive. I have dozens of those FEP bottles that you talk about Irons--I love them!!! I remember linking to them here on this site. 


Irons--Nylon is NOT base safe or acid safe--it is a condensation polymer made from an acid and an amine, a polyamide. Polyamides and esters all hydrolyze in acid or base. Phenolics are also usually base-sensitive, as is fluoropolymers (for really really strong bases, PTFE is contraindicated and PP or HDPE is preferred).


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## Barren Realms 007 (Sep 1, 2010)

contraindicated: Could you put that in english please.


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## overdriv (Sep 2, 2010)

I hope that others appreciate this discussion as much as I have... By all of your input, I have learned a lot, and that is what I was hoping for. Thank you for your input on PTFE, PP and HDPE. US Plastics has a good assortment of them.


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## Oz (Sep 2, 2010)

Barren Realms 007 said:


> contraindicated: Could you put that in english please.


Not indicated or not recommended.


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## overdriv (Sep 5, 2010)

Lou:

Your assessment of the different plastics has made a huge difference to me and I thank you. Having gotten a good dose of NOX fumes the first time I used that process, and now being very dedicated to preserving my own life and those I will work near, I heartily thank you, Lou.


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## Lou (Sep 6, 2010)

Glad to help. I just don't want people thinking they can use nylon with nitric acid and not have problems.


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## overdriv (Sep 13, 2010)

Lou said:


> Glad to help. I just don't want people thinking they can use nylon with nitric acid and not have problems.




Lou: If you could advise I would appreciate your input. Intelligent Others your input is desired as well.

I bought this fan for my fume hood and scrubber 

http://www.usplastic.com/catalog/item.aspx?itemid=23519&clickid=redirect

Because it is an 8 inch coupling required to connect to the housing of the fan, I am running into problems finding a HDPE pipe or fittings that will be resistant to the nitrogen dioxide fumes. For my Scrubber I have 1" HDPE pipe and HDPE male fittings (can only find PVC nuts to hold onto the lab hood) from the AR Fume hood/enclosed lab hood. I am really only finding either very expensive options or PVC options and there are only one or two places to buy a 8 inch to 6 or 4 inch reducers. All these are in PVC. Should I be worried about PVC failing if my scrubber is doing its job? How long would PVC last if exposed to NO2? Can it be cleaned or at the least kill any NO2 in the piping with a mild mix of water and lye? I am sorry that my questions may seem never ending. But this forum is great, and if I have questions I am sure that others should be thinking some of these things themselves. Otherwise, they may have gotten a good shot of NO2 and decided not to make this a hobby/business. For those that are thinking about making this a hobby, IT IS A DANGEROUS HOBBY. Thank you for your input, (in advance).


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## qst42know (Sep 13, 2010)

I suspect you will get a reasonable lifespan from PVC. 

http://www.vp-scientific.com/Chemical_Resistance_Chart.htm

PVC is used for plating tanks containing nitric acid solutions.


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## 4metals (Sep 13, 2010)

I have seen these exact blowers used for assay hoods without any scrubbing of the fumes (nitric from parting) in use for over 10 years with no noticeable degradation. As laboratories are exempt from the scrutiny seen by refiners by the EPA they do not scrub their assay lab exhaust.


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## Lou (Sep 13, 2010)

Well exempt as long as they're Conditionally Exempt Small Quantity Generator of hazmat waste, and even then, that depends on what they work with in their lab. Any more than 100 kg and they take notice and it keeps step with how much waste you make.


As for your question: that blower is exactly what you need. That's a smaller version of what's used in my 6' hoods.

Lou


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## overdriv (Sep 14, 2010)

Thank you all for your input. Having had a few weeks of coughing from a good hit of NO2, I want to scrub the fumes very well. Not just for my sake, but for the rest of the community. 

1. I understand that lye diluted should be used for the first scrub, exactly what is the output of that chemical reaction?

2. Also I have or read here that NO2 scrubbed with H2O and crushed marble will also give a positive result. True?

3. If there is a chlorine gas present can that be scrubbed with diluted peroxide?

Thank you for your straight answers.


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## HAuCl4 (Oct 25, 2010)

http://www.gargscientific.com/ptfe.htm

Borrowing an idea from Irons on the universal digestor vessel made of teflon with a lid.

Maybe there is a supplier in the US for these PTFE vessels. I see they have up to a 10 liter size, more than enough for most refiners out there.

Can heat the acid in a microwave oven, pull it out and then drop the metal inside for digestion.


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## Lou (Oct 25, 2010)

I have quite a bit of PTFE and FEP labware. The FEP bottles are for storing high purity acids and solutions. I have some 2L PTFE bottles and pressure reactors. They're over $800 new per piece. A 10L reactor would be absurdly expensive!



Best thing to get for bulk is a glass lined Pfaulder or an Ambi as 4metals mentioned.


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## HAuCl4 (Oct 25, 2010)

http://www.finemech.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=A136-14&Category_Code=f512&Product_Count=10

Here's a german supplier. 2 liter beaker $173. I bet chinese are even cheaper.

The Pfaudler reactor design is the one I like the most, but a deal is hard to find, and retail too expensive.

An all teflon near closed system is not hard to imagine. I'll post a design if I find the cheap pieces, for your review and consideration. 8) 

Teflon reactor on a table, teflon acid heater in a microwave oven, vaccuum buchner funnel and precipitator/separation funnel, with some tubes and stopcocks and a simple scrubber. Something like this would be very durable and hassle and fume free. 

Of course not for huge amounts, but I think for up to 50-100 Oz it would work quite nicely and trouble free.


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## HAuCl4 (Oct 26, 2010)

Any shape made to order in PTFE. I imagine they will not be cheap.

http://www.ptfeparts.com/teflon-ptfe-labware.htm

P.S.: I got a quote from this people at $6250.00 each for a 21 liter vessel, quantity 3. I'd only pay that kind of money for a reactor if a customer insisted on teflon and ruled out other choices (like pvc, fiberglass/resin, etc.) I imagine the teflon vessels would outlive several generations of refiners however. :shock:


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