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Siphoning boiling nitric using a pump.
- Thread starter Amol Gupta
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Amol Gupta
knowledgeSeaker2207
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Are there stoppers(lids) for beakers as well..?
Are they sold using a different name....?
The flasks have a round opening on the top and they are standard sizes for different size erlenmeyer vacuum flasks the 4 liter I had used for years was always a #12 stopper. The 5 liter flask has a slightly larger hole and requires a #13 stopper.
no, just a watchglass
In order to transfer into a beaker, you will have to pour the flask or set your flask up to do a gravity siphon
A watchglass is to cover the beaker he is dissolving in, I thought he was talking about the flask to use suction to remove the liquids from the parting flask.
A watchglass does not seal the beaker, it simply covers it allowing condensate to drip back into the beaker. A stopper seals the flask tightly.
watchglass
A watchglass does not seal the beaker, it simply covers it allowing condensate to drip back into the beaker. A stopper seals the flask tightly.
watchglass
Yeah...while I'd love a "sealing lid" that has a taper in it so that I could direct the fumes to a condensing column then scrubber, I've never found something that works, nor has it made it high enough on my project list to necessitate construction.
A watch glass sitting on a beaker directs the fume out the pour spout. I have had success with flexible drops that connect to a scrubber duct and simply rest on the edge of the pour spout and pick up the fume. I've done this with beakers up to 10 liter in size. 
For a while, my PVC fabricator made covers for beakers like these. They worked fine but in the end, a watch glass is as effective.
For a while, my PVC fabricator made covers for beakers like these. They worked fine but in the end, a watch glass is as effective.
Issuing the siphoning, I think that it can somehow speed up the process, but I always found decanting equally effective.
If you need to siphon, use filtering flask as catching vessel, and connect the suction hose to the top opening via stopper with hole, and vacuum source to the side arm.
As source of the vacuum, aspirator pump is superior over anything else since gasses are passed through water = majority of NOx gasses will be scrubbed. You can either attach to the faucet, or you will need recirculating membrane pump for pressure water, which is cycled in some bigger barrel.
If recirculating water, the pump needs to be resistant to at least mildly corrosive conditions as the recirculated water tends move to the acidic side.
Shops I set up usually put in a large system which handles both this simple suction flask as well as suction for multiple lots of filtration.
Shops I set up usually put in a large system which handles both this simple suction flask as well as suction for multiple lots of filtration.
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I add small amount of soda ash to counteract the acidity if needed. We had and "pseudo-automated" system, where I threw some phenolphtalein into the water 
When it lost colour, you knew pH dropped below 8 and you need to refill some base. I found out that ordinary rubber is relatively OK with mild base.
When it lost colour, you knew pH dropped below 8 and you need to refill some base. I found out that ordinary rubber is relatively OK with mild base.
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That is useful if you only vacuum acidic fumes. And for a small scale usage effective. But larger systems also are used to filter solutions dropped with metabisulfite or sulfur dioxide and those gasses then to build up and really get quite stinky. That is why the larger systems are always vented into an exhaust.
Amol Gupta
knowledgeSeaker2207
- Joined
- Dec 17, 2023
- Messages
- 207
Thanks, I'll make sure to consider an aspirator pump.
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Amol Gupta
knowledgeSeaker2207
- Joined
- Dec 17, 2023
- Messages
- 207
@4metals I have been able to find some beakers without a spout, to which I believe I can put on some lid.
I was wondering what is the material used to build the lid(is it PVC?) and what could be the expected life of the lids and any extra precautions that need to be taken when using one.
I was wondering what is the material used to build the lid(is it PVC?) and what could be the expected life of the lids and any extra precautions that need to be taken when using one.
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Those lids were made of thick PVC. The fit was snug where the PVC contacted the glass circumference to the point that some had to be sanded to fit more beakers. Apparently the beakers vary slightly in the ID. They lasted for a good many digestions before I switched to just watch glasses.
uetz2
Member
A Randolph type peristaltic is also useful for moving acids as no diaphragm is involved and only relies on the type of tubing used.
While there are benefits from a tubing pump (peristaltic) used for many chemicals, the combination of boiling nitric acid (an exceptionally aggressive oxidizing acid and even more so when hot!) and the fact that tubing that can hold up better (PTFE) doesn’t hold up well to the constant compression decompression the mechanism of a peristaltic pump uses to pump the liquid.
What type of tubing do you suggest?
uetz2
Member
As to why it needs to be boiling is concerning and I was uninformed about the faults of PTFE. I guess I need to do more research on tubing.
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I have used PTFE tubing to transfer concentrated nitric from a drum to an acid
reservoir with vacuum. But the acid is ambient temperature. Sharp bends in the tubing were the first to fail, albeit after a few years of service. I cannot imagine what the kneading of the tube would do to it.
As far as the OP saying boiling nitric acid, I assume it was because the acid parting of the Silver is done with hot acid and he didn’t want to wait for it to cool.
reservoir with vacuum. But the acid is ambient temperature. Sharp bends in the tubing were the first to fail, albeit after a few years of service. I cannot imagine what the kneading of the tube would do to it.
As far as the OP saying boiling nitric acid, I assume it was because the acid parting of the Silver is done with hot acid and he didn’t want to wait for it to cool.
uetz2
Member
Randolph manufacturers a new cilran tubing for strong acids that handles up to 190 degree F
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Thank you for that! The fix that seems to work best for the OP is suction through tubing into glassware using a good strong vacuum. Drawing acid through tubing with vacuum is less hazardous as any splits or pin holes will draw air into the hose rather than squirting acid out.
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