A Vinegaroon Experiment in Progress

[Gosut]

17 hours ago, chuck123wapati said:

YOUR iron will totally rust away long before you would ever need to fill that bottle 9 more times.

 

your math is great no doubt but what about the other 95%  of the liquid in the bottle called water ? the another variable for you to figure out as the water is also acting to dissolve the iron and it is also holding the iron in suspension also. Your making this way to hard, The vinegar is only used to hasten the iron oxidizing away if it mixes that doesn't matter.   its the quantity of iron to the tannic acid that makes the leather black. Vinegar has nothing to do with that process so it doesnt matter about how the iron and vinegar attach to each other because thats not what makes leather black.. The reaction between the iron and the tannic acid in the leather is what makes leather black not vinegar

Here is how i would get the info you want. you would need several samples (10 at least in glass jars with lids) all weighed exactly and large enough to get a measurable variance of numbers, each day or time period you designate take one sample weigh it, subtract from the original weight to find loss from evap and gassing off , take out the steel wool dry it and then weigh it. from that you can find out how much iron you have left, you can also find out how much liquid you have left, percentage of steel wool in suspension etc. you can also test the solution ( timed dip test test and total immersion) at the same time on leather that has been tested for PH to see and verify actual visual results.  you could also test different leathers with varying ph levels during your study.

Rusted iron is ferric oxide. Iron and water rusts, but I'm unclear if it's due to free oxygen in solution in the water or the water itself. If it's the water itself, it has to produce H2. My assumption is that it's due to oxygen in solution, but it's only an assumption.

The acetic acid in vinegar reacts with iron to produce ferrous acetate. That''s what reacts to the tannic acid in the leather to produce black. There's iron loss, but it's not due to oxidation.

[fredk]

Oxygen is needed to enable the corrosion. This has been proven via archaeological finds where  iron items have lain in wet peat bogs without free oxygen and the iron items are only mildly corroded. The greater the oxygen content of the environment the speedier and stronger the corrosion

[Gosut]

Even failed experiments teach something. To minimize surface area to air, I fill the 2 liter bottle to the neck. From the start I observed liquid coming out the vent hole in the cap. First I assumed that it was trapped air pushing up some of the steel wool, making it act as a plunger. But in subsequent fillings, the steel wool hasn't been near the neck of the bottle and have still observed the same effect.

I think it's the hydrogen displacing the vinegar. Because I have 49g steel wool crammed into the bottle, I think it's making it harder for the hydrogen bubbles to float to the top. Twice now I've bumped the bottom of the bottle, releasing bubbles but no more liquid, and ended up with a clear space from the cap down to the main body of the bottle. It had already pushed the vinegar out the cap, but because the hydrogen bubbles remained attached to the steel wool, the bubbles didn't rise to the top. Instead, it pushed out liquid.

Topped it off again this morning. Wondering if I should just wait a few days then pour the liquid in another bottle and discard the remaining steel wool and try again with smaller quantities.

[dikman]

Gosut, I admire your tenacity! 

Me, I just got a suitable container, poured in some vinegar from the supermarket and threw in some steel wool. I did wash the steel wool in petrol first, my token effort at a "scientific" approach!! End result was a useable vinegaroon. It's now a couple of years old (and brown) so I suppose I should try it again sometime and see if it still works.

[Gosut]

Right now I'm just waiting a few days to pour the liquid into another bottle. The liquid still shows no signs of orange and the steel wool no sign of rust. Plenty of bubbles. No sediment.

This leads to a concern: H2. My initial thought was that H2 production would be slow, dissipating through the hole in the cap. In keeping the bottle full, there's not much room to collect in large quantities, though I have gotten the aforementioned liquid coming through it as the H2 collects on the steel wool. I'm not comfortable with H2 collecting at all. I've seen lead acid batteries explode, courtesy of H2 and a short between plates. This is something different, but the Wikipedia article on H2 doesn't inspire confidence. It's possible that I'm worrying about nothing, but how much H2 was in those lead acid batteries? And you can get an electric charge on plastic and even glass. courtesy of static electricity.

I'm thinking of trying this on a much smaller scale with a wider mouth container, one open and the other with a layer of oil on top. It's frowned on now for environmental reasons, but putting a thin layer of oil on standing water is one way to control mosquitos by preventing the larva from being able to breath air. I think a little mineral oil is sometimes poured down seldom used drain traps to prevent evaporation, which would allow sewer gasses to come through the drain. But this would introduce another worry: The effect of H2 on the oil, in this case neatsfoot oil. I think a catalyst is needed for hydrogenation, though. H2 bubbles should pass through the oil. Maybe. Could try it with vinegar and a little baking soda first.

I discarded the paper towels I had underneath the bottle. It had a tie-dyed orange look, but the last spillage had some dark gray. Fine iron can oxidize quickly enough to be a fire hazard. Even steel wool can be touched off if you're not careful. Again, probably worrying about nothing, but better safe than sorry. The fresh paper towels beneath it haven't had any spillage on it yet.

Now I need a project to try it on. A simple one would be Yet Another Checkbook Cover. I would like to start on the knife sheath idea that started me in leathercraft, but I need to see about replacing the range hood before I buy more leather.  Initial plan is to cut, glue, dry, then dye with vinegaroon prior to punching the stitching holes.

Edited April 18, 2023 by Gosut
added a missing word.

[chuck123wapati]

On 4/15/2023 at 5:07 PM, dikman said:

Gosut, I admire your tenacity! 

Me, I just got a suitable container, poured in some vinegar from the supermarket and threw in some steel wool. I did wash the steel wool in petrol first, my token effort at a "scientific" approach!! End result was a useable vinegaroon. It's now a couple of years old (and brown) so I suppose I should try it again sometime and see if it still works.

mine is so old it dried out to dust now i  re hydrate it and use it anytime i'm drying out more now so i can have a stash of it on hand. I use it on my wood projects also.

[Gosut]

This afternoon noticed the steel wool floating and the neck was free of liquid. Went ahead and poured.

The liquid in the bottle was clear, the steel wool gray. I poured it into another 2 liter soda bottle, using a coffee filter and a funnel. Toward the end, the filter had picked up enough steel wool particulates that I had to change it. Think this was off the steel wool itself. Pouring the vinegaroon took about half an hour.

During this time I poured a small unfiltered bit in a quart ziplock bag, just enough to cover a scrap of 3 oz veg tan on both sides. Let it sit while I finished.

I was nearing the end when I noticed the bottle, now filled mostly with steel wool and a little liquid, felt warm. Wondered if it was my imagination. Set it down while liquid filtered into the second bottle and picked it up again. It wasn't my imagination. There was a definite warmth. Not good. Fortunately, I was just about done and I when finished, I cut open the bottle (wearing vinyl gloves for all this) and removed the steel wool. There were clear signs of rusting that had not been there before I started pouring. It had oxidized that quickly in air and the heat was likely due to oxidation. Squeezed it out best I could and disposed in an airtight container.

The vinegaroon itself has a slight yellow tint. However, it's cloudy now where it wasn't before. That may not bode well.

The test strip of leather looked black after about 20 minutes. Removed from the ziplock bag and set aside to dry. Don't know if I'll just rinse it later or neutralize any remaining acetic acid.

[Gosut]

Finally, an End to It 
The test scrap is dry and is as black as coal. May try neutralizing the free acetic acid in a solution of baking soda, followed by a dunk in some tea to replace lost tannins, followed by a rinse. Don’t know. Will be subjecting it to some bleed tests, to see if any of the black seeps out when the leather is wet. That’s beyond the scope of this topic.

I went back over the calculations from scratch and came away even more confused. My first set of calculation may be the closest to correct. Here’s why:

Once again, the formula for iron and acetic acid is Fe + 2(CH300H) = Fe(CH302)2 + H2. This means that it takes 1 iron to react with 2 acetic acids to make 1 ferrous acetate and 2 hydrogens. Chemistry uses moles to make calculations more convenient, so we can say it takes 1 mole iron to 2 moles acetic acid to make 1 mole ferrous acetate and 2 hydrogen. A mole of iron is 55.845g and 2 of acetic acid is 2 x 60.052 = 120.104g.

I first figured the amount of acetic acid in vinegar by reading an FDA regulation and assuming acidity is by weight / volume. Liquid acetic acid has a density close to that of water, 1.049g/ml, though. If we work it out with acidity as  volume / volume, then 5% acidity for 1000 ml = 50 ml acetic to 950ml water. So, 50ml x 1.049 = 52.45g per 1000 ml. 52.45g / 60.052g/mole = 0.873 moles acetic acid.

If we have 0.873 moles acetic acid per liter of vinegar, then that would react with 0.873 / 2 moles iron = 0.437 moles iron. 0.437 x 55.845g = 24.404g iron per liter of vinegar. For two liters 5% acidity white vinegar, 24.404 x 2 iron is needed = 48.404g.

This is close to where I started.

As a quick check, the ratio of iron to acetic acid is 55.845/120.104 = 0.465 x grams of acetic acid. For 104.9g acetic acid, we would need 104.9g x 0.465 of iron = 48.779g. That means 48.404g is in the right neighborhood.

This means my 49g of iron wasn’t way too much after all. But it also means that in two weeks a significant amount remained. That meant there was very little ferrous acetate in the solution I poured into another bottle. It also means that it takes very little ferrous acetate to react with tannic acid to give that nice black color, and that there’s an awful lot of free acetic acid in the solution.

There are some other things I want to try, but this experiment is at an end.

It’s also a failure, in how much iron is needed to react with all the acetic acid. That went off the rails when it pushed vinegar out the vent cap and I started topping it off. At best this is a learning experience in how not to do this sort of experiment. It also suggests that the iron should be well below the surface of the solution to prevent oxidation.

[Gosut]

I thought it was at an end. The vinegaroon now has a layer of orange floating and seemingly slowly descending from the surface. I suspect this is oxidation. It also had a white precipitate in the bottom. I suspect it has to do with pouring it through the coffee filter, either some sort of oxidation reaction or with the filter itself. Again, it was clear before I poured it. Will watch it, but in the future, would rather make it as needed than make a large batch and have it go bad.

[Littlef]

47 minutes ago, Gosut said:

I thought it was at an end. The vinegaroon now has a layer of orange floating and seemingly slowly descending from the surface. I suspect this is oxidation. It also had a white precipitate in the bottom. I suspect it has to do with pouring it through the coffee filter, either some sort of oxidation reaction or with the filter itself. Again, it was clear before I poured it. Will watch it, but in the future, would rather make it as needed than make a large batch and have it go bad.

Here's a jar of mine.  Its now just over a monthly old.  I dyed my project at 1 week.  Before I used it, I removed the steel wool, and ran it through a coffee filter.  At one week it was pretty clear, but since then its developed this delicious rusty color.  I've scooped crud off the top about once a week. But, I just dipped a scrap of leather in it, and it pretty much still instantly turned it black.  There doesn't seem to be any kind of ill effect on the leather from the vinegaroon looking rusty.  It still works great.  Just test a piece of scrap in your before you use it on a real project to make sure you get the effect you're looking for.