Gallus acid?

[Ray Rogers]

Any one know what Gallus acid is;
Is it English? or is it still in need of translation?

What effect it might have on a photographic emulsion?

There are a few googhits but I didn't find definitive data...

Cas#?
Structure?

Thanx,

or should I say Thanx anyway?

:confused:

 

[keithwms]

Should be gallic acid, I imagine. That is a precursor of pyrogallol.

 

[Photo Engineer]

Gallus acid = gallotannic acid = tannic acid. This is a polymer of a version of tannin or tannic acid. Of course there is also gallus gallus and the Roman emperor Gallus if you wish to pursue it.

I would say it could be gallic acid or tannic acid or a derivative of either. It can harden, be an antioxidant or just be a false lead. Best of luck.

PE

 

[jim appleyard]

Yeah, probably gallic acid, as Keith says.

It's used as a film developer to stain the emulsion to give a certain look.

Try a google on pyrogallol or pyrogallic acid.

 

[nworth]

Tannic acid is a bit different than gallic acid, but they are both used in iron processes to make brown-black tones. They were once used to make iron-gall inks.

 

[q_x]

I think gallic acid is used in colouring some fabrics (silk for sure).

 

[Ray Rogers]

Well ...
If something is easily oxidised, is there an implication that it is a reducer?

Gallus = Gallic?
That seems to be the big question.

It is not tannin. (and tannin is dif from tannic acid, but it (gallus acid) could possibly be tannic acid, yet one wonders...)

Gallus acid is said to be easily oxidized...
(does this mean it is a strong reducer then??)

?

 

[Michel Hardy-Vallée]

Heated gallic acid = Pyrogallol (pyro = heat).

I read in Haist that gallic acid was a developer used in the early days of photography, but once somebody figured out that the pyro version was more active, it was dropped in favor of the new kid in town.

So even pyro, the "oldest" developer still alive was once newer than something else! If they had BB in those days, they might have started a "Save Gallic Acid" campaign

 

[Kirk Keyes]

Ray - If they are talking about tannic acid, I've made developers with it. Try the formula for Pyrocat HD with tannic acid substituted for pryocatechol at 10X the conc listed for the pryocatechol as a starting point. It gives a stain very similar to the pyrocat stain.

 

[Kirk Keyes]

Also, "gallus" is German for nutgalls/gallnuts. "Gallusgerbsaure" is tannic acid.

 

[Ray Rogers]

Actually, the reason I wrote "... yet one wonders..." in
"(gallus acid) could possibly be tannic acid, yet one wonders...)" is because Gallus acid and Tannin are mentioned together in the same passage... and one asumes that were Gallus acid and Tanninc acid the same, the author would have simply said "tannin and tannic acid", unless some sort of nomenclatural or understanding change took place.

Gallus acid is said to be easily oxidized...
PE sugg it might be an "antioxidant"
you report it as being a developing agent...

Does being easily oxidized => being an anti oxident?
Does being an anti-oxident => being a reducing agent?

Too many years abroad have taken their toll on my language ability, it seems.
rr

 

[Photo Engineer]

All developing agents are reducing agents, but not all reducing agents are developing agents. All reducing agents are antioxidants but not all antioxidants are reducing agents.

There, that should help a bit! If it does not, I can give examples of all of the above.

PE

 

[gainer]

Everybody knows that galluses are them things that hold up your trousers.

 

[cowanw]

The Encyclopedia of Photography, 1879
says Gallic Acid C6 H2 (OH)3 COOH H2O occurs in fine silky yellowish crystalline needles. 1% soluble in cold water 33% soluble in boiling water.
Used by Talbot in 1835.
Used in the development of POP, intensification of collodion and gelatine plates and as an ingredient in ferrous citrate developer for chloride plates
Gallic Acid was also used in a mixture with silver nitrate, acetic acids (sic) and water to develope calotypes.
In addition, Nutgalls are used in zincography to prepare the zinc plates for the greasy ink.
Steep 4 oz. of nutgalls in 3 quarts of water for 24 hours. then boil up and strain.Add 3/4 pint of this to 1/4 pint of gum solution and 3 drams of phosphoric acid.

 

[Ray Rogers]

So the term "antioxidant" is being used in a way that includes examples of photographically interesting, yet non-developing and non-reducing compounds?

What could these be?

To what extent are non-developing antioxidants found useful in photographic (emulsion or processing) chemistry?

What role do they play?

 

[Ray Rogers]

The Encyclopedia of Photography, 1879
... Nutgalls are used in zincography to prepare the zinc plates for the greasy ink.

Thanks... 1879 is period of use I am interested in, but I think it is still unclear if there was a different compound called gallus acid, or if they are infact the same thing.

BTW, I think I have a tree load of dogwood galls. perhaps I could harvest them... are they good w\o the bug?

Ray

 

[Photo Engineer]

Sulfite is a non-developing antioxidant found useful in photographic emulsion making and processing. It is a mild silver halide solvent at high concentration as well. It is a reducing agent too.

Vitamin E derivatives are non-developing, non-reducing antioxidants used as the base for photographically, non-developing non-reducing compounds.

Hydroxyl amine sulfate is an antioxidant mild developing agent that is photographichally interesting and a reducing agent.

I could go on, but to what point. Hundreds of compounds abound that fit into many categories here. It takes years of study to grasp even a fraction of this area and Grant and I spent a lot of time discussing this subject which led to one of my patents. This is an area with a lot of grey, a lot of overlap, a lot of judgment and a need for trial and error types of R&D.

PE

 

[Ray Rogers]

Thanks...

Is there a simple test for a photographic antioxidant?
Or is that the part of grey?

 

[Photo Engineer]

The test is not simple. It is brute force and ugliness.

See the test and data in the patent I have referred to here. It basically gives this method. It is by C. Edens and R. Mowrey and outlines a standard test used at EK for this purpose.

PE

 

[Ray Rogers]

I will wade through it with a broken stick and a rain coat.
But I do have a low tolerance for brute force and ugliness; I may have to divide it up between viewings of Miriacle on 34th street and It's a Wonderful Life; Luckily I have already seen Will Smiths new movie Seven Pounds... so I am good to go for a while anyway.

Thanks

 

[Ray Rogers]

Ok, I got through that in one piece... I hurried, but it looks like antioxidant activity is being infered (not measured) from 1. increased pH stability over time and 2. improved sensitometric results.

While these results may well represent antioxidant activity, What are the antioxidants actually doing... and to which chemicals in the developer is it doing it to?　(just the developing agent itself?)

Maybe a dumb question, but how do we know that the improved stability and sensitometric results, are actually due to antioxidant activity and not something else, if the only thing being measured is pH and sensitometry?

Anyway, bottom line... to test for antioxidant activity, prepare a color developer with it and examine it for both pH stability and sensitometric behaviour and stability.

I hope I got that right.

It is about time for a movie.

 

[Photo Engineer]

Each developer was analyzed for developing agent content as a function of keeping as well if you look closely.

Therefore, more developing agent = less oxidation = better development. And, the agents are tested for development activity themselves.

PE

 

[Kirk Keyes]

What are the antioxidants actually doing... and to which chemicals in the developer is it doing it to?　(just the developing agent itself?)

An antioxidant is a molecule that counteracts or reduces oxidation reactions. Technically it applies to the oxidative effects of oxygen, it is commonly applied to any molecules that protect from any free radical (something with an unpaired electron).

Free radicals can be formed by the rupture of a bond in a stable molecule with the production of two fragments, each with an unpaired electron. These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions.

Free radicals can be formed from atoms like fluorine and chlorine, inorganic ions like hydroxyl OH-, NO2-, or ClO3-, or organic like CH3, CH3CH2, and C6H6−.

Biologically, antioxidants include beta-carotene, lycopene, vitamins A, C, and E, and certain enzymes.

Antioxidants, like BHT (butylated hydroxytoluene) are also commonly added to food products like vegetable oils and prepared foods to prevent or delay their deterioration from the action of air. BHT is also used in fuels and other commercial applications.

Sulfite, as PE mentioned, is probably the most common photographic antioxidant. And oxygen from air is probably the primary oxidative concern in photographic applications.

 

[AgX]

Also, "gallus" is German for nutgalls/gallnuts. "Gallusgerbsaure" is tannic acid.

Kirk,

Gallus is not a german word.

I guess it is a pseudo-latin term originating from the latin `galla´, which has been transformed into the german Gallapfel (both meaning: gall)


The Gallapfel contains:

Gallussäure (Gallic Acid) = 3,4,5-Trihydroxy-benzoic-acid , CAS-number: 149-91-7

and:

Gallusgerbsäure,
Gerbsäure,
Tannin,
Corilagin,
They are all the same = 3 of the above estherized with a central cyclic hydroxy-ether , CAS-number: 1401-554

 

[Kirk Keyes]

AgX - I was just reporting what I found in a vintage German-English chemical dictionary. I certainly agree "gallus" is a Latin word in origin.