A Vinegaroon Experiment in Progress

[Gosut]

AKA iron liquor. I've wanted to tinker with this since learning of it several week ago. Of particular interest is the chemistry of making ferrous acetate, the stuff that reacts with tannic acid to turn leather black. Unfortunately, I've forgotten most of what little chemistry learned in school, but I wasn't comfortable just winging it. The first question is how much acetic acid is in vinegar, in this case distilled white vinegar. The second is the chemical reaction involved. The third is the amount of iron needed to react with the acetic acid to make ferrous acetate.

Important: Before we start, every bit of what follows could be wrong.

It's been decades since I've been in a chemistry class, and all these calculations could be wrong. I'm hoping that any leatherworkers who know chemistry can comment on all this. In any event, please double check these calculations.

First, the Vinegar

The white vinegar I'm using says it's 5% acidity. But is that 5% by weight or by volume? So far, haven't found a definitive answer. An FDA regulation on vinegar implies that it's by weight; it gives grams of acetic acid to ml of water, and 1 ml of water is essentially 1 gram for the tolerance range of measuring instruments found in the home. So 5% acidity is 0.05 acidity, which should be 5g acetic acid/100ml water. For 1 liter that's 5/100 x 10/10 = 50/1000, so there should be 50g acetic acid to a liter of 5% acidity vinegar.

Next the Chemistry

Acetic acid has a formula of C2H4O2, and a molar mass of 60.052g. Iron is straight Fe, of course, and has an atomic weight of 55.845. The way chemistry is set up, I think that means iron has a molar mass of 55.845g. The reaction of iron to acetic acid is Fe+2(C2H4O2) yields Fe(C2H3O2)2 + H2. So it takes 2 moles of acetic acid to react to 1 mole of iron to yield 1 mole ferrous acetate.

How Much Iron does this Take?

Since it takes two moles of acetic acid to react to one mole iron, the ratio of iron to acetic acid by weight should be 55.845 / 2(60.052) = 55.845/120.104. For a liter of 5% by acidity vinegar, that should be 50 x 55.845/120.104 = 23.248g iron.

Maybe. There's a strong chance all this is wrong. Please double check these calculations.

Now the Experiment

For this, I used a 2 liter soft drink bottle. First I measured the full capacity of the bottle. Since the iron will take up space, I hoped it would be large enough without having to tinker with the calculations. The density of iron is 7.874g/ml, and using 2 liters of vinegar hopefully means that I'll need s x 23.248g iron, which is 46.496g iron. 46.496/7.874 = 5.9ml. So the iron and the vinegar should come to 2005.9 ml. It looked like the bottle would hold it, so I then rinsed it out and bored a small hole in the center of the cap to let out the hydrogen produced by the reaction. Two liters should take 2 x 23.248g iron = 46.496g iron. I set the kitchen scale to grams (unfortunately, it only measures to whole grams), put a paper plate on it, zeroed it out, and weighted out 47g of 0000 steel wool, then bumped it up to 49g, which both used complete bats of the steel wool on hand and gave a little excess iron. Using a funnel, I poured a small bit of iron vinegar in the bottom. Right or wrong, thought this might prevent some air spaces. Then I pulled apart the steel wool as I packed it inside the bottle. Then, with the funnel, I slowly filled the bottle with vinegar to the very top.

Hopefully, in filling the bottle to the top, that minimizes the surface area exposed to oxygen. Had thought about putting just a tad of neatsfoot or mineral oil on top to seal the surface from air, but the bottle was too full.

The plan is to wait at least a week, then pour the liquid into another bottle, using a coffee filter in a funnel as a strainer.

Now we wait.

Now, About that Ferrous Acetate

It has a molar mass of 173.993g, and 2 liters of vinegar may produce 173.993g x 46.496g/55.845g = 144.865g ferrous acetate. I think that means this yields a (144.865g / 2000g water) x 100% = 7.24% solution of ferrous acetate. That's if all this is correct.

[Gosut]

Important update:

This method has produced a miniature geyser. I don't know if it's a change in volume or just hydrogen bubbles coming to the surface, but I'm getting an almost steady flow out the top of the cap down the side of the bottle. In other words, a mess.

Fortunately, I had it outside due to the vinegar odor, and have moved the bottle to something that the vinegar won't harm. It's not something anyone would want in their house or work shop.

Why am I thinking change in volume? Grasping at straws, really. The temperature outside is warmer than inside, and wondering if the steel wool is expanding enough to force s little vinegar out of the hole in the cap.

[Wepster]

this may or may not be helpful... in another craft, it is called ebonizing wood. Here is the first reference I found, search it, it is very popular (since ebony is very expensive!)

https://www.popularwoodworking.com/finishing/ebonizing_wood/

[fredk]

37 minutes ago, Gosut said:

Important update:

This method has produced a miniature geyser. I don't know if it's a change in volume or just hydrogen bubbles coming to the surface, but I'm getting an almost steady flow out the top of the cap down the side of the bottle. In other words, a mess.

Fortunately, I had it outside due to the vinegar odor, and have moved the bottle to something that the vinegar won't harm. It's not something anyone would want in their house or work shop.

Why am I thinking change in volume? Grasping at straws, really. The temperature outside is warmer than inside, and wondering if the steel wool is expanding enough to force s little vinegar out of the hole in the cap.

Did you punch air holes in the jar lid?

[Gosut]

2 hours ago, fredk said:

Did you punch air holes in the jar lid?

Bored a hole in the center of the bottle cap. It's in a plastic 2 liter soft drink bottle. Here seems to lie some of the difficulty. I was after limiting the surface area to the air. What seems to have happened is a wad  of steel wool has collected enough hydrogen to float, in the process acting as a plunger pushing vinegar up out of the cap. Unfortunately that, and the accumulated hydrogen, has pushed out enough to leave some steel wool at the neck exposed. Have topped it off with more vinegar, which isn't ideal for this, experiment-wise. I don't know how much iron acetate I've possibly lost. True, it's likely to be slight, but it may also leave the solution with surplus vinegar. May have to scrounge up a plastic rod to push the steel wool back down.

This is surprising in that I shredded the steel wool pretty well before putting it in the bottle. Putting it through the neck of the bottle may have compressed it enough that it can give the plunger effect.

Have checked the bottle for leaks and found none.

It looks like rain could be heading this way, and have put it under a roof, in a plastic flying disk with some folded paper towels.

[Gosut]

3 hours ago, Wepster said:

this may or may not be helpful... in another craft, it is called ebonizing wood. Here is the first reference I found, search it, it is very popular (since ebony is very expensive!)

https://www.popularwoodworking.com/finishing/ebonizing_wood/

Thanks. I'll look into it. 

[Gosut]

Update: Though there was only a small bit of vinegar on the cap, I didn't like the way the steel wool was bulged up, with gas pockets visible against the side of the bottle. I took a plastic drinking straw, which wouldn't displace that much vinegar, and pressed it down, releasing gas.

Most of what came up has to have been trapped air. Although I have seen some bubbles form on the steel wool, there's been no noticeable amount dissolved. That means that even though I'd shredded the steel wool, it was compressed enough to hold air.  Once again, I think passing it through the bottleneck lead to this. Using a bottle, I'd have to tear it apart even finer and not pack so much through at one time.

Temperatures are forecast to drop, and that's going to slow the reaction.

 

[Gosut]

Update: There seem to be no more visible voids in the bottle, other than small bubbles on the steel wool. That said, the steel wool is way more intact than expected. Individual strands are visible. I would question whether the vinegar is reacting with the steel at all except that part that spilled out of the cap and onto the folded paper towel shows an irregular orange ring, with a similar spot on the remains of the label on the side of the bottle. My guess is the orange is rust where iron dissolved in the vinegar oxidized. But that it dissolved rather than formed ferrous acetate seems significant. We know that iron and acetic acid form ferrous acetate, and that iron liquor dye is made from iron and vinegar, but it seems to be taking far longer for the steel to combine with the acetic acid than anticipated.

For what it's worth, temperatures have been in the 50°'s F / 10°s C since overnight, and that has to have slowed the reaction.

[Wepster]

Again, this may or may be helpful........cleaning vinegar has about 9% acid, and you can buy concentrate  - I got some on Amazon    https://www.amazon.com/gp/product/B091FZRT1X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

plain old white vinegar is mostly water, as you noted only 4 or 5% acid.

 

[Gosut]

Update:

Even with the cooler temperatures, there are now noticeable bubbles on the steel wool, with a bubble every now and then breaking free and floating to the top. So far, no orange in the bottle itself, so hopefully there's no oxygen getting involved in this. This is why I wanted to use the soft drink bottle, filling it up to the cap in order to reduce surface area exposed to air. Not quite ready to remove the cap and inspect the surface of the vinegar.

There's problems with the bottle this full. A length of tubing attached to the top to lengthen the neck and allow for bubbles bursting at the top might be better, but don't know if it's possible to get such locally or if any exists in that diameter. Would have to cobble a connection. It would be very easy to spend a lot of money on this.

I should have used a smaller bottle, since this is an experiment. Soft drink bottles seem to be stouter than plastic bottled water bottles, and would trust them more for this, even with the vent hole in the cap.

 

[Gosut]

7 hours ago, Wepster said:

Again, this may or may be helpful........cleaning vinegar has about 9% acid, and you can buy concentrate  - I got some on Amazon    https://www.amazon.com/gp/product/B091FZRT1X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

plain old white vinegar is mostly water, as you noted only 4 or 5% acid.

 

Had thought about a higher concentration. White vinegar at 5% is easily available locally.

[chuck123wapati]

6 minutes ago, Gosut said:

Had thought about a higher concentration. White vinegar at 5% is easily available locally.

and more acid in your leather! quit jackin with it let it work a couple weeks  and go enjoy Easter my friend.

[Gosut]

The idea is that, in theory, if there's enough iron to combine with acetic acid, it should reduce the amount of acetic acid remaining in the solution to nothing. That's in theory. Actual practice is something different, though, and I don't know if this setup will result in all the acetic acid combining with iron. Likely not. I should have measured the vinegar as I poured it in, both to make sure I had the right amount and to make sure I had no air pockets in the steel wool. Since I had to add vinegar to make up the amount lost, as an experiment this is already a failure in that I won't know if it's possible to completely combine iron with acetic acid with such a set-up.

Started wondering just how much hydrogen this should yield. By the formula, it takes 2 moles of acetic acid to yield 1 mole hydrogen. If there's 100g acetic acid in 2 liters of 5% acidity white vinegar, and the molar mass of acetic acid is 60.052g, then 100/(2X60.052) = 0.833 moles hydrogen. Hydrogen has an atomic weight of 1.00784, so H2 should have an atomic weight of 2.0157. 2.0157 x 0.833 = 1.679g hydrogen. Hydrogen has a density of 0.8988g/liter at normal temperature and pressure,, so 1.679 / 0.08988 = 18.687 liters hydrogen. If this calculation is correct (big if), that's a lot of hydrogen. Now I don't know if the displaced vinegar Friday was due to air trapped in the steel wool when it put it in the bottle or from the reaction.

If correct, though, that yield of hydrogen shows why it's so important to allow the iron and vinegar mixture to vent. 

 

[Gosut]

Update:

The vinegar has dropped slightly in the neck of the bottle, with no signs of leaks. That had me wondering how much drop would I see from the reaction. What follows is horribly slip-shod because I've forgotten the particulars about solutions. I'm going to have to break out an old chemistry text.

My reasoning, slipshod as it is, is that the 46g iron that I used for calculations has a volume of 5.905 ml. Added to 2000ml of vinegar gives 2005.905 ml. The 100 g of acetic acid in the 2000 ml vinegar  would be 95.829ml. So, 2000 - 95.829 = 1904.171ml water.

If all the iron combined with acetic acid, that would give 144.865g ferrous acetate, which would have a volume of 83.544 ml. Added to 1904.171 = 1987.715 ml. 2005.905 - 1987.715 = 18.19ml  drop in the vinegar.

Again, note I've forgotten what little I knew about solutions, so these calculations may not be correct. It does look like my goal of keeping a minimal surface area exposed to air will mean topping it off more. I've already messed up this part of the experiment by adding vinegar to fill up the voids, so the result is going to contain more acetic acid than I hopped. OTOH, so far the liquid is clear.

[Littlef]

8 minutes ago, Gosut said:

Update:

The vinegar has dropped slightly in the neck of the bottle, with no signs of leaks. That had me wondering how much drop would I see from the reaction. What follows is horribly slip-shod because I've forgotten the particulars about solutions. I'm going to have to break out an old chemistry text.

My reasoning, slipshod as it is, is that the 46g iron that I used for calculations has a volume of 5.905 ml. Added to 2000ml of vinegar gives 2005.905 ml. The 100 g of acetic acid in the 2000 ml vinegar  would be 95.829ml. So, 2000 - 95.829 = 1904.171ml water.

If all the iron combined with acetic acid, that would give 144.865g ferrous acetate, which would have a volume of 83.544 ml. Added to 1904.171 = 1987.715 ml. 2005.905 - 1987.715 = 18.19ml  drop in the vinegar.

Again, note I've forgotten what little I knew about solutions, so these calculations may not be correct. It does look like my goal of keeping a minimal surface area exposed to air will mean topping it off more. I've already messed up this part of the experiment by adding vinegar to fill up the voids, so the result is going to contain more acetic acid than I hopped. OTOH, so far the liquid is clear.

I think you're putting way more thought behind this, than is necessary.  I just did a vinegaroon belt pouch for round balls.  I filled a pickle jar with vinegar, and jammed 2 4x steel wool pads in it on a Tuesday.  On Saturday I blackened my leather.  I didn't take a single measurement.      - your level is dropping because vinegar is mostly water, and water evaporates because you made a vent hole in the jar lid.  Its not hurting anything.     Also, its nice when the mixture remains clear, but it still works just fine when it develops some sludge from the steel wool rusting.  

[mdawson]

On 4/8/2023 at 12:59 AM, Gosut said:

 

Hey Gosut

I've made a couple of batches of vinegroon but have been struggling to understand the chemistry, I forgot how to do all this stuff decades ago, never used it since high school.

I wouldn't worry about the little extra vinegar you put in, unfortunately the strength written on the vinegar bottle is likely rounded off so the results are always going to be 'within experimental limits'.

Looking forward to your conclusions in a week or so.

Mark

[chuck123wapati]

9 hours ago, Gosut said:

Update:

The vinegar has dropped slightly in the neck of the bottle, with no signs of leaks. That had me wondering how much drop would I see from the reaction. What follows is horribly slip-shod because I've forgotten the particulars about solutions. I'm going to have to break out an old chemistry text.

My reasoning, slipshod as it is, is that the 46g iron that I used for calculations has a volume of 5.905 ml. Added to 2000ml of vinegar gives 2005.905 ml. The 100 g of acetic acid in the 2000 ml vinegar  would be 95.829ml. So, 2000 - 95.829 = 1904.171ml water.

If all the iron combined with acetic acid, that would give 144.865g ferrous acetate, which would have a volume of 83.544 ml. Added to 1904.171 = 1987.715 ml. 2005.905 - 1987.715 = 18.19ml  drop in the vinegar.

Again, note I've forgotten what little I knew about solutions, so these calculations may not be correct. It does look like my goal of keeping a minimal surface area exposed to air will mean topping it off more. I've already messed up this part of the experiment by adding vinegar to fill up the voids, so the result is going to contain more acetic acid than I hopped. OTOH, so far the liquid is clear.

 

8 hours ago, Littlef said:

I think you're putting way more thought behind this, than is necessary.  I just did a vinegaroon belt pouch for round balls.  I filled a pickle jar with vinegar, and jammed 2 4x steel wool pads in it on a Tuesday.  On Saturday I blackened my leather.  I didn't take a single measurement.      - your level is dropping because vinegar is mostly water, and water evaporates because you made a vent hole in the jar lid.  Its not hurting anything.     Also, its nice when the mixture remains clear, but it still works just fine when it develops some sludge from the steel wool rusting.  

yea pretty much , here's the deal the vinegar is simply to speed up the process of reducing the iron(rusting it away) and putting it in a liquid suspension . You could use plain water but it would take much longer than the vinegar. It doesn't have to be exact in any way and its about as sciency as putting a mento in diet pop. 

If you use stronger vinegar then you also put stronger acids on your leather which isn't good, neither would be the oil you wanted to put on top of the mixture to keep out air. Remember the end result is to produce a liquid you can put on leather, dye it black, and not ruin it.

There are more than a couple of threads on this topic it may be good to read through some of them, there are also other ways to make the roon.  

Good luck!!! 

 

[Gosut]

On 4/10/2023 at 9:53 PM, Littlef said:

I think you're putting way more thought behind this, than is necessary.  I just did a vinegaroon belt pouch for round balls.  I filled a pickle jar with vinegar, and jammed 2 4x steel wool pads in it on a Tuesday.  On Saturday I blackened my leather.  I didn't take a single measurement.      - your level is dropping because vinegar is mostly water, and water evaporates because you made a vent hole in the jar lid.  Its not hurting anything.     Also, its nice when the mixture remains clear, but it still works just fine when it develops some sludge from the steel wool rusting.  

I drive my wife up the wall with my insistence on using measurements when cooking.

"I just add some salt," she might say

""But how much?" I ask. "How long do you let it cook?"

"I don't know. I just as it until it looks right."

That works well for her, but for a simpleton like myself, who only cooks on rare occasions, that's frustrating. I don't have the experience to know what "looks right."

Same thing here. Like soap making, people were making iron liquor long before they understood exactly what was going on, and some of those old timers got mighty good results by eyeballing ingredients. But, like those soap makers of old, others got mixed results. Which is how homemade soap got the reputation of being harsh, because some ended up with excess lye.

With vinegaroon, my question is the amount of free acetic acid, Ideally, an exact combination of iron with acetic acid should yield none, but I doubt that's possible with this kind of set-up. There will be some. If we neutralize it, we introduce sodium bicarbonate to the leather, but simply applying sodium bicarbonate might have bad effects on leather. Yes, I know free acetic and tannic acid would combine with the baking soda, but how much is left in the leather? So many unknowns.

Basically, I want to understand what's going on chemically, and come up with a working recipe for personal use. Some of what I thought would work has already gone out the window, but that in itself teaches something. OTOH, so far there's no orange in the solution itself, so minimizing surface area exposed to air might help. OTOH, would have to do the same thing in a wide mouth container with the steel wool completely submerged in the vinegar to see if it's the smaller surface area or just keeping the steel wool away from oxygen.

[Gosut]

On 4/11/2023 at 1:58 AM, mdawson said:

Hey Gosut

I've made a couple of batches of vinegroon but have been struggling to understand the chemistry, I forgot how to do all this stuff decades ago, never used it since high school.

I wouldn't worry about the little extra vinegar you put in, unfortunately the strength written on the vinegar bottle is likely rounded off so the results are always going to be 'within experimental limits'.

Looking forward to your conclusions in a week or so.

Mark

Thanks. I really am ready to dust off my old chemistry text book and start at the front. Have forgotten way too much of this stuff.

This morning it looks like I may be getting significant dissolving of the steel wool. However, that could be shifting due to hydrogen forming on the steel wool and moving it around slightly in the liquid. Will wait and see.

[Littlef]

3 hours ago, Gosut said:

I drive my wife up the wall with my insistence on using measurements when cooking.

"I just add some salt," she might say

""But how much?" I ask. "How long do you let it cook?"

"I don't know. I just as it until it looks right."

That works well for her, but for a simpleton like myself, who only cooks on rare occasions, that's frustrating. I don't have the experience to know what "looks right."

Same thing here. Like soap making, people were making iron liquor long before they understood exactly what was going on, and some of those old timers got mighty good results by eyeballing ingredients. But, like those soap makers of old, others got mixed results. Which is how homemade soap got the reputation of being harsh, because some ended up with excess lye.

With vinegaroon, my question is the amount of free acetic acid, Ideally, an exact combination of iron with acetic acid should yield none, but I doubt that's possible with this kind of set-up. There will be some. If we neutralize it, we introduce sodium bicarbonate to the leather, but simply applying sodium bicarbonate might have bad effects on leather. Yes, I know free acetic and tannic acid would combine with the baking soda, but how much is left in the leather? So many unknowns.

Basically, I want to understand what's going on chemically, and come up with a working recipe for personal use. Some of what I thought would work has already gone out the window, but that in itself teaches something. OTOH, so far there's no orange in the solution itself, so minimizing surface area exposed to air might help. OTOH, would have to do the same thing in a wide mouth container with the steel wool completely submerged in the vinegar to see if it's the smaller surface area or just keeping the steel wool away from oxygen.

sure, nothing wrong with wanting to understand how things work.  Enjoy the experiment!

[chuck123wapati]

17 hours ago, Gosut said:

I drive my wife up the wall with my insistence on using measurements when cooking.

"I just add some salt," she might say

""But how much?" I ask. "How long do you let it cook?"

"I don't know. I just as it until it looks right."

That works well for her, but for a simpleton like myself, who only cooks on rare occasions, that's frustrating. I don't have the experience to know what "looks right."

Same thing here. Like soap making, people were making iron liquor long before they understood exactly what was going on, and some of those old timers got mighty good results by eyeballing ingredients. But, like those soap makers of old, others got mixed results. Which is how homemade soap got the reputation of being harsh, because some ended up with excess lye.

With vinegaroon, my question is the amount of free acetic acid, Ideally, an exact combination of iron with acetic acid should yield none, but I doubt that's possible with this kind of set-up. There will be some. If we neutralize it, we introduce sodium bicarbonate to the leather, but simply applying sodium bicarbonate might have bad effects on leather. Yes, I know free acetic and tannic acid would combine with the baking soda, but how much is left in the leather? So many unknowns.

Basically, I want to understand what's going on chemically, and come up with a working recipe for personal use. Some of what I thought would work has already gone out the window, but that in itself teaches something. OTOH, so far there's no orange in the solution itself, so minimizing surface area exposed to air might help. OTOH, would have to do the same thing in a wide mouth container with the steel wool completely submerged in the vinegar to see if it's the smaller surface area or just keeping the steel wool away from oxygen.

 

I too love a good experiment and am looking forward to someone who can for once say it takes x amount of steel wool in y amount of vinegar of a given strength for z amount of days to get a solution of ?% iron That works on leather with ? amount of residual tannic acid. 

How did you set up your experiment? How much steel wool did you use? how much vinegar? By now you should have data that suggests how much the steel wool is reduced daily by the vinegar.  How have your measured that?

What is your method to find out how much iron in solution and tannic acid it takes to achieve Black in an average piece of leather?

what is your method for testing the residual tannic acid in leather?

 

[chuck123wapati]

18 hours ago, Gosut said:

Thanks. I really am ready to dust off my old chemistry text book and start at the front. Have forgotten way too much of this stuff.

This morning it looks like I may be getting significant dissolving of the steel wool. However, that could be shifting due to hydrogen forming on the steel wool and moving it around slightly in the liquid. Will wait and see.

here is an archive of tons o books on leather science.

 this site a good start on finding  what you want just search leather   but this book has info on your speriment you may need. https://archive.org/details/dli.bengal.10689.10394

[chuck123wapati]

18 hours ago, Gosut said:

Thanks. I really am ready to dust off my old chemistry text book and start at the front. Have forgotten way too much of this stuff.

This morning it looks like I may be getting significant dissolving of the steel wool. However, that could be shifting due to hydrogen forming on the steel wool and moving it around slightly in the liquid. Will wait and see.

https://archive.org/details/pub_american-leather-chemists-association-journal

[Gosut]

On 4/13/2023 at 7:12 AM, chuck123wapati said:

 

I too love a good experiment and am looking forward to someone who can for once say it takes x amount of steel wool in y amount of vinegar of a given strength for z amount of days to get a solution of ?% iron That works on leather with ? amount of residual tannic acid. 

How did you set up your experiment? How much steel wool did you use? how much vinegar? By now you should have data that suggests how much the steel wool is reduced daily by the vinegar.  How have your measured that?

What is your method to find out how much iron in solution and tannic acid it takes to achieve Black in an average piece of leather?

what is your method for testing the residual tannic acid in leather?

 

As experiments go, this one has already gone off the rails. It's just steel wool, measured out on a paper plate on a kitchen scale, in a 2 liter plastic soda bottle filled with 5% acidity vinegar. There is no way to  remove the steel wool except by cutting open the bottle. Didn't weigh the bottle before putting in the steel wool and vinegar, so I can't simply pour out the steel wool and weigh it. Even if I did, residual liquid in the steel wool would throw off the results. There's no way other than weighing the steel wool to determine how much dissolved, and the moment I take it out of the bottle and dry it, it's wet steel wool exposed to air, and will oxidize some. I didn't premeasure the vinegar before hand and have topped it off, so even that's out the window. So basically, I have steel wool in a bottle with vinegar and I look at it and go "Yep, there's bubbles on it and the liquid and steel wool shows no orange of rust (or ferric acetate - have learned that's a thing, too), It doesn't even seem to have significantly dissolved the steel wool in a week's time.

That raises the question you brought up: How much ferrous acetate does it take to turn tannic acid black? If most vinegaroon leaves a significant amount of the iron intact, that implies it takes very little. At this point I could remove a tad with a dropper and see what happens to a piece of veg tan scrap, but that's about all. I don't know if I can even measure the tannic acid content in brewed tea to get some idea.

Memories of titration keep coming back, but that means having some sort of indicator for what I want to measure and something that will react to it, not to mention a precise way to measure it.

Am wondering if it would have been better to measure out a small amount of steel wool and vinegar. Doubt a kitchen scale could weigh a single 0000 steel wool strand, but just one with the predicted amount of vinegar might be better for this.

[Gosut]

As to chemistry books, I'm was about to crack open my college textbook, but then found one by Linus Pauling, General Chemistry. So far it strikes me more as high school level, but that's just three chapters in. Don't know yet why he covered calculating the distance of atoms in a solid, but wonder if he will tie it in with electrons and chemical bonds. Pauling's text is from the early 1970s, but figured that for the basic stuff, it should be fine.