Got Tannic Acid, can I make pyrogallol from it?

[Kirk Keyes]

Condensed fraction of the tannin will not be effective in development.

Do you say this because of the size of the tannic acid molecule? There does seem to be an issue with how would a molecule the size of tannic acid get into the emulsion to do the development, without the tannic breaking down some it seems somewhat improbable. Otherwise, there seems to be a lot of 1,2-dihydroxy- and/or 1,2,3-trihydroxybenzenes around the perimeter of tannic acid.

Anyway, tannic acid is an indeterminate compound mixture of plant origin. We can get better developers of known composition and purity at a lower price. I don't see a reason to go for tannic acid despite all the practical problems and lack of precise knowledge.

Anyway - it does seem to be an interesting curiosity, and it works a lot better than reports I've seen for Caffenol or Urinol does...

 

[Ryuji]

Do you say this because of the size of the tannic acid molecule?

No, but more simply, condensed tannins are not soluble enough to be useful.

Otherwise, there seems to be a lot of 1,2-dihydroxy- and/or 1,2,3-trihydroxybenzenes around the perimeter of tannic acid.

That's not sufficient for a developer, as I said. Those hydrolizable fraction fragments contain carboxyl group from the ester that broke off from the central sugar. This carboxyl group pulls electron away from the benzene ring and weakens the reducing power of the polyhydroxybenzenes. This is why gallic acid is a very lousy developing agent. Same applies to tannic acid fragments.

Also, in order for a developing agent to be superadditive with Phenidone, the developer must be a significantly more strong reducing agent than Phenidone. HQ, catechol, pyrogallol, ascorbate all meet this condition but not ones with acid attached to the ring. (And this extends to why Metol is a better developer than Glycin.)

Also, as you acknowledged, if di- or polyhydroxybenzenes are indeed generated in the solution to act as the developer, it's best to buy those agents of known quality right at the beginning, rather than relying on uncertain and unsure nature of tannic acid. Safety, etc. wouldn't apply anyway. If you want to argue safety, I'd use the minimum quantity of useful active agent and none of inactive and useless compounds that may arise from tannin.

 

[jim appleyard]

Speaking of Urinol, should I mix it with lots of beer first?

 

[Ryuji]

Maybe, if it's Guiness.

Red wine might be better.

 

[desertrat]

Pyrogallol from Tannic Acid

At the risk of incurring the wrath of the real chemists here, which I'm not, you can make pyrogallol from tannic acid, but it's not simple. In the fewest possible words, you can make gallic acid from the tannic acid by treating it with dilute sulfuric acid, then precipitating out the gallic acid. You can make pyrogallol from the gallic acid by heating it to 220 degrees C and holding it there for awhile. Carbon dioxide is given off and it turns to pyrogallol. The process is not easy or simple, but I was sure I had read about it somewhere and did a little googling. Here are some links.

http://www.henriettesherbal.com/eclectic/kings/acidum-gall.html
http://www.henriettesherbal.com/eclectic/kings/acidum-tann.html
http://171.64.128.245/library/monographs/monckh/notes.html

In the third link, see note 7. You would have to want pyrogallol really bad and have absolutely no other way of getting it to resort to these methods. Disclaimer: This stuff is from the late 19th century, for information only, do not do this in your kitchen.

 

[Ryuji]

At the risk of incurring the wrath of the real chemists here, which I'm not, you can make pyrogallol from tannic acid, but it's not simple.

I didn't describe it as procedual steps, but the description I dropped in my previous posts gave the information on how gallic acid can be made from hydrolyzable fraction of tannin.

Again, as I said before, condensed tannin is covalently bonded and they don't break easily, even with sulfuric acid. Only hydrolyzable fraction will break the esters to make gallic acid and glucose. From there, you could separat gallic acid by precipitation, and heat it to lose the carboxyl group, like you said.

But in reality pyrogallol is readily available and it is cheap.

 

[sun of sand]

I read a few years ago researching homemade gall inks used for writing that you can turn tannic acid into gallic acid then gallic acid into pyrogallic acid

pyro just stands for heat treatment of the gallic acid, right

 

[desertrat]

A couple of years ago I downloaded from the Internet Archive a photography manual from the mid-late nineteenth century that gave specific instructions on making pyrogallol from oak galls. I don't have the link anymore, but some keyword searching in Google Books should turn up something.

This link has some info:

http://books.google.com/books?id=2c...a=X&ei=AVNNU-WmFcGbygG9oYDYAQ&ved=0CFwQ6AEwCQ

 

[Gerald C Koch]

Pyrogallol is so very toxic you don't want to be making it. Just too many chances for accidents. The minimum lethal dose LDLo is 28 mg per kg of body weight. If you insist on using this chemical then buy it and use it with all the necessary safety precautions. As a chemist I would not even have it in my house.