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Poll: Is it always necessary to clean all glass after distillations?
I wash everything, every time --- 25 (75.76%)
I wash everything if the distillate is relatively nonvolatile (e.g. conc. H<sub>2</sub>SO<sub>4</sub>;) --- 7 (21.21%)
Only three-way and thermometer adapters -- 0 (0%)
I never wash glass after distillations --- 1 (3.03%)

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Author: Subject: Is it always necessary to clean all glass after distillations?
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[*] posted on 8-2-2014 at 20:58
Is it always necessary to clean all glass after distillations?

I always clean all my glassware after every distillation, but as most involved substances are relatively volatile, I'm beginning to doubt whether this is necessary (excluding the boiling flask, of course).

After distilling DCM from paint stripper, for example, would you wash the condenser and take-off adapter? What about the three-way/thermometer adapters?
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[*] posted on 8-2-2014 at 21:21

Should be an option for 'give everything a quick rinse', because that's what I do. Voted for the first choice.

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[*] posted on 9-2-2014 at 04:31

Depends on what I distill.

If it is inorganic and soluble, a quick rinse do the job, but generally I will take a few min per piece to be sure nothing could go wrong with the next experiment.

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[*] posted on 9-2-2014 at 04:44

Even with volatiles I wash all of the apparatus. If the compounds are soluble in water, then I wash with distilled water. Otherwise, I use a suitable volatile solvent for washing.

The reason of washing is that sputtering or tiny droplets, taken with the vapor, may make it into other pieces of glassware than just the boiling glass. I want to be 100% sure that in the next experiment I do not spoil things due to dirty glassware. Better having an extra wash and spoiling some time, than spoiling the complete yield of a precious compound.

I do not do distillations very often, so I do not find it a problem if every few months or so I need to spend some extra time to cleanup things.

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9-2-2014 at 06:31
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[*] posted on 9-2-2014 at 06:56

No, it isn't always necessary to clean up after distillations. Cleaning glassware takes time and resources and you need to weight if that is worth it in the grand scheme of things. If I am running batches of a material, I might be going into the glassware with the same thing. If that's the case I might not even discharge the pot residue but merely charge on top of it. Sometimes I have cleaned in place when running similar compounds. Charge solvent to the pot, distill some over, empty the receiver and the pot, charge in the next compound. And then sometimes when I am purifying solvents I hardly clean anything at all, if you're distilling ether from sodium wire, the pot might need cleaned at the end, but everything else is ether wet, by the time you pull it apart it is clean and dry. And just how clean you need your glassware depends on scale size. A 25 mL flask needs to be much cleaner than a 22L flask simply because of the surface area to volume ratio. You could have a 22L completely coated in a thin film of contaminating material but it's only going to be a fraction of a percentage impurity and when your starting material might be only 98% pure it's kind of a moot point whereas for the 25mL flask you're risking contamination that might cause issues with interpreting NMR and GC data.

[Edited on 2/9/2014 by BromicAcid]

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[*] posted on 17-2-2014 at 13:33

I like your advice bromic. its practical.
It reminds me of when I see people rinsing and drying their beakers only to fill them with a water solution.

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[*] posted on 17-2-2014 at 15:21

Cleaning Vigreux columns is a pain which I try to avoid if possible. I usually just rinse them out with water.

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[*] posted on 22-2-2014 at 03:48

Normally we wash everything with water and acetone with a bit of scrubbing to get all the "heavy shit" off, before the glass goes in a dishwasher-like contraption. To be fair, the dishwasher machine is likely overkill, quite often the glass ends up cleaner than it was beforehand after 5 minutes of cleaning with paper towels, acetone and water.

However, Bromic is probably correct - washing is not always needed, but IMO it is good practice to get into. Especially if you do a lot of analytical stuff :)
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