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coltoiletpaper
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[*] posted on 7-4-2018 at 16:57
Technical grade acetone purification


Hey guys, it's my first post here on sciencemadness. I have been told that there are nice individuals here that can help me out with both home chemistry and some questions that may arise during my apprenticeship as a laboratory assistant.

I got this acetone from the hardware store used for lacquer thinning and distilled it once with a vigreux column.
I discarded everything before 54°C and started collecting afterwards until 56°C. I stopped at 56°C because there wasn't whole lot left in the flask and the temp was still rising.

I'm quite puzzled since the b.p. of acetone is 56°C and my largest fractions were at 54 to 55°C and 55 to 56°C with about equal volume. Is this stuff really THAT impure? Also it was rather cold and I did it outside but insulated my stuff a bit with aluminium foil. Could have that thrown off my thermometer even though I had a steady and high collection rate?

I personally would redistill that stuff again with a vigreux column and look for the temp on the thermometer when it's warmer outside in the afternoon. I hope that someone could advise me on how to proceed with that stuff and if I can get it clean enough for some synthesis.
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[*] posted on 7-4-2018 at 17:07


Sounds like you are doing exactly the right thing.
There are a few things that can cause temperatures to be off. I typically get a degree or two lower than expected in distillations which I put down to thermometer position and geometry.
Yes, the stuff is that impure. But how pure do you need?
It also probably contains some water. You can take additional steps to dry it - I would do that befkre redistillation. But again, how dry does it need to be for your purposes?




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XeonTheMGPony
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[*] posted on 7-4-2018 at 18:16


don't forget to factor in elevation!

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[*] posted on 7-4-2018 at 18:23


Quote: Originally posted by XeonTheMGPony  
don't forget to factor in elevation!

And I always do. I am about 700m above sea level which is enough to make a difference.




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[*] posted on 7-4-2018 at 20:00


same here every thing is 1 degree lower, but I was more so referring to the OP! As it is important to know why your results are skewed.

OP: Take some steam distilled water, heat it up slowly, the second it comes to a steady boil note the temperature. Next place a beaker in the freezer till ise just forms, take it out and let sit till the ice just starts to melt, place thermometer in the ice/water mix and note temp once stable.

This will tell you where the top and low end of the thermometer is, most important is the boiling point one as this will get you a reference to find your altitude and calibrate all other boiling points
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[*] posted on 7-4-2018 at 22:30


Quote: Originally posted by XeonTheMGPony  
same here every thing is 1 degree lower, but I was more so referring to the OP! As it is important to know why your results are skewed.

OP: Take some steam distilled water, heat it up slowly, the second it comes to a steady boil note the temperature. Next place a beaker in the freezer till ise just forms, take it out and let sit till the ice just starts to melt, place thermometer in the ice/water mix and note temp once stable.

This will tell you where the top and low end of the thermometer is, most important is the boiling point one as this will get you a reference to find your altitude and calibrate all other boiling points


This is all good advice, except the beaker in the freezer part. The proper way to calibrate a thermometer is in a saturated solution of crushed ice. The way you have described "place it in the freezer until ice just forms" will NOT give an accurate reference for 0°C. Also, don't forget your beaker in the freezer, you might find it in pieces in the morning.
Take note of how much you have to immerse your thermometer in both the hot and cold solutions to get an accurate reading. The different volatility at freezing and boiling can mess with readings. I also suspect OP is having thermometer placement discepancies as well as a bit of water. He didn't specify what his temperature eventually reached, but he seemed to imply that it rose higher than 56°. Dry acetone doesn't do that, even when you distill the last bits, IME.
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coltoiletpaper
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[*] posted on 8-4-2018 at 01:25


Quite a few replies, nice!


Quote:

But how pure do you need?


I have no idea if my plan even comes as far but it seems like I could maybe have some issues later on, but I don't need it dry since I will add water in the next step. But I have no clue how pure I need it since I haven't found open-source literature or even just some home chemists that described that synth. It seems to be possible though, but I'm left in the dark. Only one way to find out.


Quote:

don't forget to factor in elevation!


Didn't think of that one. 428m above sea level in my region. I'm too dumb to find a phase diagram of acetone right now.


Quote:

This is all good advice, except the beaker in the freezer part. The proper way to calibrate a thermometer is in a saturated solution of crushed ice. The way you have described "place it in the freezer until ice just forms" will NOT give an accurate reference for 0°C. Also, don't forget your beaker in the freezer, you might find it in pieces in the morning. Take note of how much you have to immerse your thermometer in both the hot and cold solutions to get an accurate reading. The different volatility at freezing and boiling can mess with readings. I also suspect OP is having thermometer placement discepancies as well as a bit of water. He didn't specify what his temperature eventually reached, but he seemed to imply that it rose higher than 56°. Dry acetone doesn't do that, even when you distill the last bits, IME.


I was using an analogue alcohol thermometer so I can't calibrate it, but I will check anyways today as I had no time yesterday (I still need to get a glas tube for the probe of the digital thermometer). The temp rose above 56°C on my thermometer afterwards with a very small amount of acetone remaining in the flask. I just stopped it because it was freezing outside and I wanted it done. Since it was tech grade from the hardware store I would guess there is some water present. And for thermometer placement: I placed the bulb with the alcohol right in front of the turn in the adapter where the condenser connects. I was taught that placement in the apprentice lab of the company and it would be kinda silly to place the thermometer lower as it would go into the column.

[Edited on 8-4-2018 by coltoiletpaper]
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XeonTheMGPony
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[*] posted on 8-4-2018 at 04:42


well you aren't calibrating the therm, you're calibrating your self! once you match it up to your elevation and note any off sets and this allowes for accurate consistent readings from then on out.

I spend the extra money for a tight tolerance mercury thermometers but I even do that still!

Happy: You caught me I over simplified, bad habit, all so you don't leave it in freezer over night lol why I said when ice forms, that's when ya crush it and allow it to reach equilibrium. Easier then building a laser cryogenic cooling system to start at near absolute zero! (would be fun though!!)

I use the standard of placing the bulb just inline with the top of the ground joint this allows a bit of lead time in temps for knowing when to cut the distillation with a bit of safety net, still requires care full monitoring.

I all ways distill tech grade acetone, usually dry it while doing so, but if you read the posted paper I will be trying the recommended methods, it was sourced from a few different places one of which was wiki so do not take the information as correct but test it first.

I'm a bit obsessed with purity so will be continue researching methods. This thread will be a perfect dumping ground for the methods I find, in fact could make a good sticky?
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[*] posted on 8-4-2018 at 06:22


Quote:

well you aren't calibrating the therm, you're calibrating your self! once you match it up to your elevation and note any off sets and this allowes for accurate consistent readings from then on out.


I ran a larger setup with more acetone. First I had some predistillate of which I got about 50ml before collecting (left some white solid and some oily odorless liquid, checked after those 50ml and that left nothing). I guess I had not enough volume to get a fraction at a stable temperature because it sat stable at ~54.5°C now and after that 55°C and then started rising slowly even above 56°C again. I collected both 54.5-55° and 55-56°C again since both are about equal volume. Gonna read out the temp with boiling water and redistill all my acetone over CaCl2 tomorrow and see then.


Quote:

I spend the extra money for a tight tolerance mercury thermometers but I even do that still!


You can still get mercury thermometers in the EU? One would think mercury is banned here. Gonna look out for one.

My previously distilled acetone is leaving a really tiny amount of white stuff upon evaporation, it seems to be solid (not sure how that works, could it be phenol?). Gonna see if I can get it any purer with CaCl2 and multiple runs.

[Edited on 8-4-2018 by coltoiletpaper]

[Edited on 8-4-2018 by coltoiletpaper]
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[*] posted on 8-4-2018 at 06:45


It does not matter if your thermometer uses mercury, alcohol or any other liquid.
Calibration is the same, and necessary - unless you can afford calibrated thermometers.
The liquid used will be suitable for the temperature range of the thermometer,
we should treat ALL thermometers as un-calibrated and check them ourselves.
For me, melting ice and boiling water (with correction for atmospheric pressure) are good enough checks on accuracy.

To be really sure of the purity/b.p. of your acetone ideally you should check the accuracy of your thermometer at 56oC +/- atmospheric pressure compensation.
The easiest would be to record your local atmospheric pressure and put your thermometer in a test tube of boiling pure acetone ;)

Some thermometers are calibrated for total immersion in the fluid to be measured,
many have a calibrated immersion depth, typically 75mm/3", the level of immersion will be printed on the thermometer, or there will be a ruled line showing calibrated immersion depth.
If a thermometer is used other than at its calibrated depth then 'stem correction' can be applied.
https://pubs.acs.org/doi/abs/10.1021/i560146a026?journalCode...




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coltoiletpaper
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[*] posted on 8-4-2018 at 07:45



Quote:

It does not matter if your thermometer uses mercury, alcohol or any other liquid. Calibration is the same, and necessary - unless you can afford calibrated thermometers. The liquid used will be suitable for the temperature range of the thermometer, we should treat ALL thermometers as un-calibrated and check them ourselves. For me, melting ice and boiling water (with correction for atmospheric pressure) are good enough checks on accuracy. To be really sure of the purity/b.p. of your acetone ideally you should check the accuracy of your thermometer at 56oC +/- atmospheric pressure compensation. The easiest would be to record your local atmospheric pressure and put your thermometer in a test tube of boiling pure acetone ;) Some thermometers are calibrated for total immersion in the fluid to be measured, many have a calibrated immersion depth, typically 75mm/3", the level of immersion will be printed on the thermometer, or there will be a ruled line showing calibrated immersion depth. If a thermometer is used other than at its calibrated depth then 'stem correction' can be applied.


My thermometer indeed has a marking on it. It's a line and when it's aligned with the top of the adapter screw it sits right in front of the turn. I will be testing all that stuff that you guys have posted in the next week. Thanks alot for your help!
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[*] posted on 8-4-2018 at 08:20


Correction for elevation is only applied to calibrated meteorology station air pressure, when you don't have your own barometer and instead use reports of others.

One can tell if the thermometer is in the right place by moving it around and seeing what happens.




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[*] posted on 8-4-2018 at 08:26


Quote: Originally posted by coltoiletpaper  
... I was using an analogue alcohol thermometer so I can't calibrate it, ...

Sure you can, just that you'll need to adjust the readings manually instead of tweaking a control.

Thermometers follow the rule $$y=mx + c$$
where:
y = the Real reading
x = what the thermometer says
m = a correction factor
c = a constant offset.

To calculate m and c, follow the advice above to get your thermometer's readings at 0 C and 100 C.
We'll call the 0 C reading x1 and the 100 C reading x2.

Now we get
$$y_1=mx_1+c, y2=mx_2+c$$
so
$$y_2 - y_1 = mx_2 + c - mx_1 - c$$
c cancels itself out
$$y_2 - y_1 = mx_2 - mx_1$$
$$y_2 - y_1 =m(x_2 - x_1)$$
$$m=\frac {y_2 - y_1}{x_2 - x_1}$$
then calculate c
$$c =y_2 - mx_2$$
From then on, use those m and c values to convert that thermometer's reading (x) into a real and accurate value (y) with the original formula:
$$y = mx +c$$
That's one thermometer calibrated - m and c will be different for other thermometers..




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[*] posted on 8-4-2018 at 09:41


Quote: Originally posted by S.C. Wack  
Correction for elevation is only applied to calibrated meteorology station air pressure, when you don't have your own barometer and instead use reports of others.

One can tell if the thermometer is in the right place by moving it around and seeing what happens.


When you see a weather map with isobars, or pressure announced,
it is corrected for altitude above sea level,
so if you use a weather report to get your local atmospheric pressure,
you need to adjust for your local altitude.
(if not, isobars would mostly follow topography)

I use a domestic weather barometer and/or my diy mercury manometer/barometer ;)
--------------------------------------------------------------
y = m.x + c is an approximation as m = f(y)
(capillary tubes are often not of constant cross-sectional area,

IF y = m.x+ c then only a two-point calibration is required,
this is why I recommended a three-point calibration,
with the ideal situation where one of the calibration points is the actual temperature to be measured.

I have attempted to calibrate my 'best' thermometers (Quickfit and Fisons)
I was unable to to get repeatable results at sufficient accuracy to detect errors in my thermometers.
For -5 to +50 oC I have two accurate mercury thermometers in my psychrometer that I can use as a reference.

Surprisingly, the cheap thermometer that came with my cheap Chinese 500ml distillation kit was accurate at water m.p. and b.p.
and a quick test of the even cheaper looking thermometer that came with a cheap set of three hydrometers/alcoholmeters showed no significant error.

Sorry for derailing from acetone to thermometers,
>99.9% acetone is reasonably priced via eBay UK so I have no purification experience and I seem to have verbal diarrhoea or similar lately.
Most of my >99.9% acetone has been used for drying glassware after washing or as a solvent,
no actual acetone-based chemistry that I recall :(

[Edited on 8-4-2018 by Sulaiman]




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[*] posted on 8-4-2018 at 11:33


Now days the greater majority of therms are pretty well on the money for pretty well all of our needs, it is just that pesky altitude thing can throw you for a loop if it isn't factored in. but it is a good habbit to ensure it is mostly correct, not like you can read fractions of a degree on a analog therm!
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[*] posted on 8-4-2018 at 11:46


Quote: Originally posted by Sulaiman  
... I recommended a three-point calibration, ...

For Amateur purposes any kind of calibration will usually work fine, sometime no calibration at all.

In a distillation what the thermometer shows the experienced distiller is temperature Change rather than an absolute precision measurement.

Yes, a rough idea is also required and precision temperature reading of vapor temperature is obviously better.

In reality, you'll cut fractions when the temperature changes, not when it hits precisely 56.001375689 C for 12.2298 seconds

When you start getting into 3 point calibration and 4, maybe 5 decimal places, then there ceases to be a distinction between Amateur and Professional work, apart from the money of course.




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[*] posted on 8-4-2018 at 23:03


Do the 54-55 and 55-56 fractions display different physical and chemical properties? Basically, can you test them if one is acetone and the other isn't, or one is mostly acetone and the other is mostly something other?



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[*] posted on 8-4-2018 at 23:11


I've distilled solvent grade acetone a few times; it is typically pretty pure (at least 99%) but with some unknown crud in it that you wouldn't ordinarily notice if you evaporated a few drops on a watch glass, but the residue is definitely noticeable if you distill a few liters. If you're using the acetone for Jones reductions, it's not a bad idea to reflux it in chromic acid before distilling, although that's probably unnecessary unless you are working with extremely dilute solutions.



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[*] posted on 9-4-2018 at 09:01


Quote:

Do the 54-55 and 55-56 fractions display different physical and chemical properties? Basically, can you test them if one is acetone and the other isn't, or one is mostly acetone and the other is mostly something other?


I couldn't spot a difference (maybe only a slight one upon burning, the higher boiling one gives off a tiny bit of black smoke, lower one doesn't). Both leave a bit of a white residue upon evaporation. I'm gonna redistill today over CaCl2 and see what happens (I collected a tiny amount of both seperately to check that but in the end collected both fractions in the same bottle since I was gonna redistill anyways). The odor of the bottle is faintly fruity (ester-like) but also causes this wierd, sharp and stinging feeling in my throat which I also had with pure ethyl acetate. Does acetone usually have that smell? (gosh, smells are hard to describe and descriptions are hard to interpret)


Quote:

I've distilled solvent grade acetone a few times; it is typically pretty pure (at least 99%) but with some unknown crud in it that you wouldn't ordinarily notice if you evaporated a few drops on a watch glass, but the residue is definitely noticeable if you distill a few liters. If you're using the acetone for Jones reductions, it's not a bad idea to reflux it in chromic acid before distilling, although that's probably unnecessary unless you are working with extremely dilute solutions.


I'm gonna do some polymer chemistry with that acetone and I've seen some users report problems of rapid polymerization in their flask when distilling the crude product if impurities are present. Also I have a hard time getting chromium compounds, even just tiny amounts. They seem to be restricted in the EU/Germany.
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[*] posted on 9-4-2018 at 09:30


"Commercial acetone may be purified in several ways :— (a) The acetone is refluxed with successive small quantities of potassium permanganate until the violet colour persists. It is then dried with anhydrous potassium carbonate or anhydrous calcium sulphate,f filtered from the desiccant, and fractionated : precautions are taken to exclude moisture.

(b) To 700 ml. of acetone, b.p. 56-57°, contained in a litre bottle, a solution of 3 g. of silver nitrate in 20 ml. of water is added, followed by 20 ml. of iV-sodium hydroxide solution, and the mixture is shaken for about 10 minutes. The mixture is then filtered, dried with anhydrous calcium sulphate, and distilled.

(c) When only a relatively small quantity of pure dry acetone is re-quired, it may be purified through the bisulphite compound : the latter is decomposed with sodium carbonate solution (for details, see under Methyl ethyl ketone, 14), dried over anhydrous calcium sulphate, and distilled.

A more convenient procedure is to make use of the addition compound with sodium iodide (NaI,3C3H60), which decomposes on gentle heating and is particularly well adapted for the preparation of pure acetone. One hundred grams of finely powdered sodium iodide are dissolved under reflux in 440 g. of boiling commercial acetone, and the solution is cooled in a mixture of ice and salt ( — 8°). The crystals are filtered off, and quickly transferred to a dry distilling flask, connected to an efficient condenser and to a receiver cooled in ice. Upon gentle warming, the acetone distils rapidly. Pure acetone has b.p. 56-2°/760 mm., and is highly inflammable."

-From Vogel's Practical Organic Chemistry, from the forum library
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[*] posted on 9-4-2018 at 14:42


Quote: Originally posted by coltoiletpaper  
I'm quite puzzled since the b.p. of acetone is 56°C and my largest fractions were at 54 to 55°C and 55 to 56°C with about equal volume. Is this stuff really THAT impure?
Sounds to me like you haven't done many distillations. Unless you have a reflux and a steady state, head temperatures can and do vary, easily by a few degrees. Think of it this way, a standard vigreux column has difficulty separating components 15C apart. It's not worth discriminating between 1-2 degrees when that is the case.


What were you using for your heat source? Unless you were using a mantle with a constant voltage there is oscillation there. Was your column insulated? If not then you're affecting your equilibrium there. Honestly, if I were working in my back yard I would have collected the whole fraction from 54-56 as acetone without a second thought. Do some qualitative tests on your distillate if your curious, check it for aldehydes, alchohols, etc. My bet would be it's good acetone.




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[*] posted on 9-4-2018 at 21:04


Quote: Originally posted by BromicAcid  
Quote: Originally posted by coltoiletpaper  
I'm quite puzzled since the b.p. of acetone is 56°C and my largest fractions were at 54 to 55°C and 55 to 56°C with about equal volume. Is this stuff really THAT impure?
Sounds to me like you haven't done many distillations. Unless you have a reflux and a steady state, head temperatures can and do vary, easily by a few degrees. Think of it this way, a standard vigreux column has difficulty separating components 15C apart. It's not worth discriminating between 1-2 degrees when that is the case.

What were you using for your heat source? Unless you were using a mantle with a constant voltage there is oscillation there. Was your column insulated? If not then you're affecting your equilibrium there. Honestly, if I were working in my back yard I would have collected the whole fraction from 54-56 as acetone without a second thought. Do some qualitative tests on your distillate if your curious, check it for aldehydes, alchohols, etc. My bet would be it's good acetone.


This. It's easy to tell those who haven't had a lot of practical experience in the lab from posts like the one made by the OP. (However, don't worry, we all started off like you did, and you only find out through experience, or asking on a forum such as this.)

Another angle to think about it is this: what other compound could they possibly have used to dilute the acetone 50% yet has a BP within 2 degrees of acetone? No likely candidates come up, and so you can be quite confident that the anything coming over between 53-58 degrees is pure acetone.
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[*] posted on 13-4-2018 at 13:09


Quote:

This. It's easy to tell those who haven't had a lot of practical experience in the lab from posts like the one made by the OP. (However, don't worry, we all started off like you did, and you only find out through experience, or asking on a forum such as this.) Another angle to think about it is this: what other compound could they possibly have used to dilute the acetone 50% yet has a BP within 2 degrees of acetone? No likely candidates come up, and so you can be quite confident that the anything coming over between 53-58 degrees is pure acetone.


You're correct on that one. I have done one simple distillation at the lab and this one at home, no more. And I guess I won't need distillation in a long time at the lab. Further, I started working in the lab at the first of september last year and since the start of this year I've been in a molecular biology lab.


Quote:

Sounds to me like you haven't done many distillations. Unless you have a reflux and a steady state, head temperatures can and do vary, easily by a few degrees. Think of it this way, a standard vigreux column has difficulty separating components 15C apart. It's not worth discriminating between 1-2 degrees when that is the case. What were you using for your heat source? Unless you were using a mantle with a constant voltage there is oscillation there. Was your column insulated? If not then you're affecting your equilibrium there. Honestly, if I were working in my back yard I would have collected the whole fraction from 54-56 as acetone without a second thought. Do some qualitative tests on your distillate if your curious, check it for aldehydes, alchohols, etc. My bet would be it's good acetone.


I was using an oil bath and had some aluminium foil as insulation but that was it. I will just continue with my plan not worry about the acetone too much.

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