As I was cleaning my windows with vinegar and water, I realized that I don’t even know what vinegar is made from. What is it?
Acetic acid /əˈsiːtɪk/, systematically named ethanoic acid /ˌɛθəˈnoʊɪk/, is an acidic, colourless liquid and organic compound with the chemical formula CH3COOH (also written as CH3CO2H, C2H4O2, or HC2H3O2).
The real question is – once you’ve made wine or cider, how do you keep it from turning into vinegar?
Vinegar is made from wine, cider, or similar liquids by the action of acetic acid bacteria (acetobacter), which consumes the ethanol and leaves acetic acid behind.
If you deliberately want to make vinegar, you add a “vinegar mother” – liquid containing live acetic acid bacteria – to your starting mix, and the bacteria do the rest.
To keep wine from turning into vinegar, you try to keep such acetic acid bacteria away from your wine. Sterilize everything beforehand to kill any acetobacter that might have gotten in. Use a vapor lock to keep air from getting in. You can store your wine in a cool place. or treat it with a chemical like potassium sorbate, or kill the bacteria with heat (pasteurization)
I’ve had one of these for many years and never had a bottle go bad no longer how long it sits.
Vinegar is made (naturally) by acetobacter bacteria, which needs oxygen so a closed container is enough to discourage growth. It’s normally spread by fruit flies. Vinegar used to be an expensive condiment until they discovered how to use the ‘mother’ to make more quickly. It’s naturally something of a slow process.
It makes an excellent stop bath for making darkroom prints.
When I set up my new darkroom, with somewhat limited air circulation, I did one session and decided “Nope!”; the delightful fragrance of acetic acid was just a bit too strong for my taste.
I immediately switched over to using citric acid for the job. It doesn’t last as long as traditional acetic acid stop bath, but at least it doesn’t stink. And it’s super easy to whip up a fresh batch for each session–one tablespoon of citric acid in 1000ml of water.
You’re mixing your units. Shouldn’t it be 15ml (possibly 15g, if it’s in powder form) to 1000ml of water?
Is there something wrong with that? It seems sensible in this application. They probably measure out water in liters and just think of how many big spoons they need to put in. If you google “one teaspoon per liter” with the quotes, you’ll get plenty of examples of people using this form. Heck, I’ve seen dosages listed as mg/lb before.
It just bugs me, probably because yesterday I was cruising FB and I came upon a recipe video, where the narrator was giving quantities in metric format, then specifying an oven temperature of 350F. Who uses metric quantities and Fahrenheit cooking temperatures?
I gotta admit, the mg/lb dosage convention is a little weird.
Was this by any chance a baking recipe? Because there it would be not unusual to do so.
ETA: For example, I bake bread with metric weights, but think of temperature in Fahrenheit. Come to think of it, any salt and yeast I add I think of in terms of teaspoons.
Or, just drink the wine within a day or so (maybe a bit longer if you use a vapor lock). 
It takes longer than that to turn into vinegar but the process has started and the wine will be off in taste pretty fast (day or so…depends).
Why? If someone is using metric measurements for quantities, instead of cups, tablespoons and ounces, I’d expect that their oven would be set for degrees Celsius. Do British and Canadian ovens have their temp dials marked in degrees Fahrenheit?
ETA: My red-blooded all-American Bisquik box never asked me to go out and buy a scale to properly measure how much mix to use in the Impossible Cheeseburger Pie recipe. Or a new set of measuring cups for the milk.
Acetic acid is also used as a curing agent. That’s why you smell vinegar when you apply silicone sealant around your bathtub.
I’m with @pulykamell. I live in the US (actually not all that far from @pulykamell although we have never met) and I tend to use metric for measurements (although recipes vary so have to adapt but on my own it is metric) but, for some reason, I always set my oven in Fahrenheit. Dunno why. I guess I just have an intuitive sense for how “hot” something is using that and never bothered to train myself otherwise.
Also, using Fahrenheit seems fine. Metric measurements are great since they are so easily convertible but I don’t need to convert temps when cooking. Oven needs to be “this” hot, set dial to “that” hot and done.
If the recipe is for an American audience, bakers use something called bakers percentages, and they’re easiest to figure out if the units are in metric.
So, was this a baking recipe you saw this in?
Canadians do, apparently. From the Wikipedia article on their metric conversion, which started in 1970 and stalled in 1985:
Surprisingly, as in the United States, a conservative government took power in the 1980s and that’s why metrication stopped. But Canada did start the conversion much earlier than the U.S., and continued it for several years after the U.S. stopped, so it got much further along.
There was meat involved, so maybe roasting (but it was ground beef and puff pastry, so maybe baking).
And I’d expect that if it was intended for an American audience, it wasn’t for American bakers; it was for American grandmas who’ve been using the same set of measuring cups and spoons for sixty years.
So I don’t care to speculate as to the target audience.
ETA: So, how 'bout that vinegar, eh? Is it tart, or what?
I just re-watched this like a day ago:
Of note, the acetic acid molecule is very similar to the ethanol (drinking alcohol) molecule, just with two of its hydrogens replaced by an oxygen.