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Registered Member #2563
Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280
Hello i'm going to try to concentrate my H2SO4, Ive built a small fume hood for it, to put far away from my house while i do this, with a long wooden dowel to turn the hotplate off, Going to boil it down.. Would it be fine to boil it in a standard Pyrex beaker? and then store the conc H2SO4 in a glass Reagent Bottle with a glass stopper? or should i use a rubber stopper. And also, what sort of pipette would the acid effect if any. Because as i understand it wouldn't affect those small plastic ones, but Ive had them quite easily split at the sides. so would a glass one with a rubber end be better suited? sorry if anything i'm asking is unclear.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
How about unplugging the hotplate at the end of an extension cord. What is the SG of your acid and what do you want the final acid to be. Do you have a car battery hydrometer to test it? Will anything you plan to do cause release of H2? The thermostat on the hotplate could cause an ignition spark. Acid, glass, parts of hotplate will be flying everywhere.
Sorry to be such a bother but I have seen just how far parts of batteries have been launched in electrical faults.
Registered Member #2563
Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280
That will work too, ill just unplug it. The SG is 1.28 - 1.24 i think so its fairly dilute. id like it to be as close to pure as possible like 98% at least. Nothing i plan to do will release any hydrogen. Thanks for the tips as well. also no i do not have a hydrometer.
Registered Member #2261
Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581
Good luck! Hot concentrated Sulphuric Acid is very nasty stuff so don't take any risks as you won't have time to rinse it off, and when you do, it'll burn you a second time. Plan for when the beaker cracks and the contents spill out. Don't have water anywhere near it while it's hot. A particular problem with boiling near concentrated H2SO4 is that the water, or dilute H2SO4 that boils off tends to condense and drip back down into the boiling H2SO4 where it causes a sudden huge release of heat which splashed acid everywhere which could crack glass as well as spray you and your equipment. The more you enclose it to keep the spray in, the more drips of condensation you get... The white fumes are noxious and very corrosive. Don't let the fumes blow near anything made of steel that you value. I use polythene pipettes, but agree they split too often. Just take this into account when using them. Glass and rubber would be better if you keep the acid off the rubber as it will probably attack it depending on what type - test it. The best container for conc. H2SO4 is a HDPE bottle as it won't break when dropped. Otherwise use glass with a suitable plastic top or a ground glass stopper. To be honest I don't think boiling is a very practical way to concentrate H2SO4. Better to expend your effort trying to find a way to buy it.
Registered Member #2563
Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280
There is no way to buy it around here, tried and true. What other way could i concentrate it while keeping it cheap and practical? thanks for the info on the pipettes also.
Registered Member #2272
Joined: Wed Aug 05 2009, 01:34AM
Location:
Posts: 7
It is indeed a risky task. My suggestion is to keep the temperature just below boiling point, so that it will evaporate but not boil and risk to spill over. Do this outside definitely, and once the volume of your acid has decreased, weigh it to determine its concentration (based on the original weight of the diluted acid. Concentrate it down to the level where you'll feel comfortable to go... I wouldn't try over 70% this way.
Let it cool down for a while before handling the vessel and very carefully pour (with a glass funnel if possible) into your final container. As suggested above, HDPE would be perfect, but keep em away from the sun because UV+HDPE=bad ... -Robert
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
where are you located? - there might be a place not far from you that might have access, you never know.
as for doing it yourself, with concentrating acid take every precaution. Whenever I do something like this that might involve shattering glass and dangerous chemical splashes, I use a blast shield. I don't think it would be a bad idea to have a polycarbonate shield between you and the glassware if possible (I don't think polycarbonate would react seriously with h2so4, you might check first but if it does I doubt it would be worse than having the spray go everywhere). You can buy glassware designed for distilling, a basic retort might do the trick if you take care with accidental fume release and control the temperature such that the acid condenses as it leaves the neck of the glass, or use a condenser with it.
rubber gloves, an apron, goggles and a face shield are a must, as well as standard safety procedure.
and if you doubt yourself doing this, don't do it!
Registered Member #2998
Joined: Tue Jul 13 2010, 08:34PM
Location: Swedish forests.
Posts: 26
If you're in a fume hood or outside you pretty much have your problems solved. It's not rocket science boiling H2SO4 to concentration, as long as you observe the safetyprocedures (glasses, gloves, apron etc). Believe me, hot concentrated sulphuric is an evil evil thing.
Anyhow, just boil away and vent the fumes out untill you can see a transition between two different types of smoke. The latter will be the sulphuric boiling, and there will be a distinct pause in between with almost no fumes at all. This is when you've boiled off the water and only has H2SO4 left. I typically wait for the "second stage" to kick in before aborting. Put a lid on the container to keep the air moisture from getting to it, wait for it to cool and voilah.
Registered Member #2563
Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280
HVgeek wrote ...
If you're in a fume hood or outside you pretty much have your problems solved. It's not rocket science boiling H2SO4 to concentration, as long as you observe the safetyprocedures (glasses, gloves, apron etc). Believe me, hot concentrated sulphuric is an evil evil thing.
Anyhow, just boil away and vent the fumes out untill you can see a transition between two different types of smoke. The latter will be the sulphuric boiling, and there will be a distinct pause in between with almost no fumes at all. This is when you've boiled off the water and only has H2SO4 left. I typically wait for the "second stage" to kick in before aborting. Put a lid on the container to keep the air moisture from getting to it, wait for it to cool and voilah.
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conc H2SO4
