How long and at what temperature would I have to heat wine to make sure all the alcohol was gone? If, say, I start with 1/5L?
Raise the temperature of the wine until it begins boiling (about 190 degrees). Continue boiling until the temperature reaches 212 degrees (or slightly less, depending on the sugar content). At this point all the alcohol is gone. And it won’t taste like wine anymore.
It’s important to know why one would want to do this - for cooking purposes, as an example, the alcohol present in the wine is essential in extracting spices and flavor e.g. Spaghetti sauce.
But, you can’t do this, can you? I mean, you can’t get rid of all the alcohol and still keep any water. They codistill because they have too high a mutual affinity. You can’t get all the water out of alcohol by distillation, you have to resort to other means like molecular sieves to prepare anhydrous alcohol. Wouldn’t you be able to get all the water out of alcohol with a still if you could get all the alcohol out of water with a still?
Religious convictions might be one reason.
I am acquainted with several Muslims who do not drink alcohol and have convinced themselves that when cooking with an alcoholic beverage (like the wine in a beef stew), the heat causes all the alcohol to evaporate off. Although I am not familiar with the technical details that Napier describes, I have read an article by a food chemist that agrees that alcohol, despite its volatility, doesn’t suddenly all boil off, any more than all water would suddenly boil off when the temp reaches the boiling point.
I have chosen not to try and disabuse my acquaintances of their notion.
Not suddenly, but eventually. Alcohol lowers the boiling point of the solution it is in (in this case, stew); the solution cannot retain the alcohol over that temperature. As more and more of the alcohol evaporates, the temperature of the stew rises, until it reaches the boiling point of water (or slightly less, due to sugar and other ingredients). At that point, for all intents and purposes, all the alcohol is gone. Are there stray molecules left? Probably, but not enough to quibble over.
I believe it’s the reverse, you can’t get all the water out of alcohol thru conventional distilling, because together they are azeotropes. The best you can get is something that’s 95% alcohol, 5% water.
I’m not positive, but that’s what my cursory review of azeotropes online suggests.
If there is significant alcohol in the solution, it will depress the boiling point. When the solution reaches the boiling point of water, nearly all the alcohol is gone.
Kinda the whole point of distilling to make strong spirits.
To the OP:
A preferrable technique is to use a vacuum pump to reduce the pressure over the liquid to ~59mmHg (the vapor pressure of ethanol near room temperature) This will allow the alcohol to be distilled from the mixture without overly oxidizing the remainder.
If you condense what comes off the wine, you’ll have brandy.
If your vacuum pump can’t get down there, you can apply a little heat.
Here is an on line calculator that will give you the relationship.
>because together they are azeotropes
Yes, Qadgop, that’s it.
I think the principle is symmetric, but most of the literature would describe trying to get all the water out. After all, who needs to start with liquor to get water?
But if you set out to separate a bottle of mix into a bottle of alcohol and a bottle of alcohol, and you can’t get all the alcohol into one bottle, why would you be able to get all the water to stay in the other?
Water and ethanol are so mutually attractive that mixing a liter of one with a liter of the other doesn’t even make 2 liters of mix.
Well, my lab techniques manual says that all of the ethanol will have boiled off once the mixture reaches 100 C; the solution behaves as an azeotrope between the boiling point of ethanol (slightly lower, actually) and that of water. You wouldn’t be able to get all of the water in a mixture separated out, but simple distillation would let you separate a water/ethanol mix into <95% ethanol and pure water.
You can get all the alcohol out of the water. You just can’t get all the water out of the alcohol by distillation. The asymetry is due to the higher boiling point of water. Even when frozen, water has a non-zero vapor pressure, so there is no temperature at which you can cause the alcohol fraction to evaporate without some of the water also vaporizing.
The fraction of water that is included in the vapor is proportional to the ratio of the vapor pressures of the two components at the distillation temperature, and also proportional to thier concentration in the liquid. As the alcohol is boiled off, the temperature of the liquid rises, and proportionally more water is included. When the temperature reaches 100C, only water is leaving, because that temperature reliably indicates that the liquid contains no alcohol.
But to play devels advocate, assume there was some ethanol left. At 100C, the vapor pressure of water is one atmosphere (760mmHg) and the vapor pressure of ethanol is over 2 atmospheres (1693mmHg). Any trace of alcohol will have a strong propensity to remain as vapor.
>When the temperature reaches 100C, only water is leaving, because that temperature reliably indicates that the liquid contains no alcohol.
Well, then, why does household ammonia solution still have ammonia in it? Room temperature is way, way higher than anhydrous ammonia’s boiling point. Doesn’t its affinity hold it there, if not in equilibrium then at least as a function of time?
Adding water to either alcohol or ammonia raises its boiling point. Likewise, adding either to water lowers the boiling point. The point isn’t that at 212 degrees, all the alcohol will disappear. The point is that if there was alcohol still in it, the boiling point would be lower.
Also, as I understand it, ethanol keeps a strong hold to 5% water. That’s why you have to add another chemical to make alcohol stronger than 95%. Water won’t latch on to alcohol in the same way though. Obviously you can have pure water. It’s happy by itself, unlike alcohol. So really, you can’t remove all the alcohol without removing at least some of the water, but you don’t have to remove all of it. And you can add water to make up for whatever evaporated.
>adding either to water lowers the boiling point…if there was alcohol still in it, the boiling point would be lower
Ah, makes sense.
>Obviously you can have pure water.
It’s obvious you can have pure water or pure alcohol. Do you mean it’s obvious you can make pure water by distillation?
>add another chemical to make alcohol stronger than 95%
You mean my molecular sieves? I’d argue they’re not a chemical - well, everything is, but I’d argue they aren’t undergoing some kind of bonding operation, they’re acting physically, as is the inner wall of the boiler.
Gee, it must work, but - I’m looking for something that’s not symmetric about water and alcohol that would let you get one more free of the other than you could the other free of the one. Of course boiling point is asymmetric. I don’t know how to tell what asymmetry is enough, though. So I still don’t see why distillation could generate pure water, but also think it must be able to because you could keep heating the water till its boiling point reaches 100, as you point out - so it’s still mysterious but looks like it has to work. Hmm.
I revive this thread since WhyNot provided a cite that answers the OP’s original question for all practical purposes over in this thread for a similar discussion. Basically, normal cooking methods do not completely remove alcohol from a dish.
I think that answers the question definitively enough to merit revival of a week-old thread.
Since you already revived this thread I will add my own little tidbit. If you started with an ethanol concentration above the azeotrope (~96%) and heated it to the boiling point of ethanol, you would end up with pure (or really, really close to it) liquid ethanol. I thought this might help alleviate some of Napier’s symmetry concerns.