Due to their many uses, alcohols can be found in a wide range of products. Here is another attempt at extracting an alcohol, this time ethanol, a very useful basic laboratory reagent, from its function as a disinfectant in hand gels. I run into a few problems with the viscosity of the gels, but overall it is a nice, simple extraction – just requiring one or two distillations and some drying – providing a product pure enough for some uses around the lab.
Ethanol is an extremely useful organic solvent, great in dissolving a range of polar and non-polar compounds. It finds its place as a reactant in many reactions also; I have an esterification reaction lined up for mine to make some fruity-smelling esters. It is also quite easy to make commercially by the process of fermentation.
Despite this, ethanol can be, depending on location, quite difficult to obtain for a home chemist – this is seemingly the case for me. Because ethanol is a recreational drug, forms such as alcoholic drinks are quite dilute and large alcohol taxes keep the prices expensive. I have attempted to extract another alcohol before in a previous blog post, propan-2-ol, from food dyes, but there wasn’t much to extract in the end.
I have been looking for a better source of alcohols for a while, and recently stumbled upon the fact that many antiseptic gels contain a large proportion of alcohol – often ethanol.
I managed to get hold of a product which contained 50ml of the gel, about 41g, with the concentration of 70g of ethanol in every 100g of the gel. That is 70% ethanol by weight – a potential of 28.7g of ethanol. The only problem is this brand of gel is very viscous, so is going to be very hard to work with, especially as I am opting to separate the ethanol by distillation.
There is a serious risk of liquid catching fire; its vapour may catch fire above 13 °C. The vapour / air mixture is explosive (from 3.3 to 19% ethanol).
Breathing vapour may result in sleepiness: the concentration in the air should not exceed 5,760mg m-3.
- Gloves and goggles should always be worn when handling chemicals to protect your sensitive eyes and skin.
- Work in a well ventilated area and avoid any nearby naked flames due to the flammability of ethanol and to avoid breathing any vapours in.
- I would say your main safety worry here is just boiling a liquid at a temperature high enough to scald you (80ºC), and to watch out for the slight chance of possible foaming of the boiling flask once the solution begins to boil with some products (although the product I used did not have this problem).
I transferred the gel to a 250ml round bottom flask using a funnel, although this was quite difficult as the gel refused to slide down the funnel. In the end, the persuasion from a couple of portions of 50ml of distilled water did the job. The gel container was washed thoroughly to get every last drop of the gel out.
The consistency in the flask was still very thick and I was afraid that this would lead to uneven heating or potential foaming. In the end, I added a total of 250ml of distilled water to the original gel, including the funnel steps. This is not ideal, as you are also diluting the ethanol. On hind-sight, this was not actually a problem, and so if I repeated this experiment I would use much less water, if possible none; otherwise use a different, less viscous brand of antiseptic gel, which I may do in the future.
Nevertheless, we must continue forward! I set up for simple distillation. I would recommend a fractionating column if you have one.
Ethanol has a boiling point of 78.4ºC, water has an obvious boiling point of 100ºC, but less obvious is the boiling point of a water and ethanol mixture – 78.2ºC – lower than either water or ethanol separately! This is due to a common phenomenon called azetropes. Water and ethanol form an azetrope, both boiling together at 78.2ºC to form vapours of the composition 95.63% ethanol and 4.37% water (by weight). This means that any ethanol we distil over will only be a maximum of 95.63% ethanol – keep this in mind.
A stir bar was added and strong stirring was turned on along with medium heat. It took a little while but eventually the solution began to boil with the thermometer reading around 80ºC which is about right for the azeotrope.
Soon after, the first drops of distillate began to come over. Using a pipette, I transferred a few drops of the distillate on to the bottom of a beaker, then providing a flame to see if the distillate was flammable. It was very flammable, and caught fire immediately to product a lovely, clean blue flame. This is a basic qualitative test for ethanol, showing ethanol is coming over.
The apparatus was left to continue running, although I regularly checked the still head thermometer temperature and the volume of distillate. If the temperature started to increase above the 80ºC I was distilling at, this would signal that the azetrope has finished and just water will start to boil over. Also, as mentioned in the introduction, 28.7g of ethanol, or 36ml of ethanol, was the theoretical yield, so I did not want to distill over more than 36ml of liquid.
In the end, I stopped the distillation after collecting 32ml of distillate – I would have liked to leave it longer but it was getting quite late in the day, and other projects required my attention. Ideally, to remove most of the water, the distillate should be redistilled to guarantee an azeotropic distillate of ethanol and water, and then dried using a drying agent such as anhydrous copper(II) sulfate. I will be just using the ethanol to make esters, and therefore a little water won’t harm the reaction much. Also redistillation and drying would cause some ethanol to be lost and I am more interested in quantity, not quality, due to aiming to make these esters (once I can get hold of some reasonably pure carboxylic acids that is!).
Talking of yields, if the theoretical yield of ethanol based off the product information is 28.7g, and our actual yield was 25g, then:
(25 ÷ 28.7) × 100 = 87%
So I managed a yield of 87%, although I imagine a significant percentage of this is due to water contamination, so I would expect the ethanol recovery to be much lower. I believe I made a mistake by adding so much water, and I would recommend to try find a brand of gel that is as thin as possible, emptying many of these into a flask and just boiling this without adding any extra water if possible.
I definitely want to revisit this extraction, although first I may try extracting the ethanol from concentrated alcoholic spirit drinks to see if this is an easier extraction for ethanol – the third episode of whats turning into an alcohol extraction series I guess! At this comment though, I will mention that college exams are approaching fast and so this post will mark the last for a few months until around July. College chemistry has priorities unfortunately; I look forward to my return in the summer where I will have loads of time for all sorts of projects. Until then!