Ascorbic acid solution life

[nworth]

There is a well known problem of Kodak Xtol and possibly other ascorbic acid based developers going dead after a while. This has been ascribed to any number of things, including iron contamination. Recently I was watching a PBS Nova program on the Franklin expedition to the Northwest Passage. The members of the expedition got stuck. Eventually they developed scurvy, even though they had lemon juice as a source of vitamin C. The narrative noted that Vitamin C loses potency in solution over a period of time. One possibility for this is racemazation of the L-ascorbic acid. That would affect people but not developers. There is also a possibility of other reactions which actually destroy the compound. Does anyone know any more about this and its potential affects?

 

[3Dfan]

This might help - http://unblinkingeye.com/Articles/Preserv/preserv.html

 

[gainer]

A 10% solution of ascorbic acid in propylene or ethylene glycol can be made and has quite a long life until water is added.

 

[nworth]

This might help - http://unblinkingeye.com/Articles/Preserv/preserv.html

This may or may not describe the reaction. Lemon juice is quite acid (citric acid, among other things), yet the ascorbic acid deteriorates in time. The time is quite a long time, however.

 

[gainer]

Unfortunately, the reaction that oxidizes ascorbic acid produces, in two stages, dehydroascorbic acid which is slightly more acidic than ascorbic acid. The fact that the oxidation product is somewhat more acidic indicates that acidity will not alone preserve ascorbic acid. Oxygen from the air and other active molecules oxidize the aascorbic acid and leave it acidic.

The human body makes dehydroascorbic acid to get it across the brain blood barrier, then converts it back to vitamin C. I'm pretty sure it's not the kind of reaction we would be able to do in a developer stock solution.

Ascorbic acid lasts a long time in dry state. If you mix it in water that has been boiled to remove most of the gases, it will last a long time, and longer if you keep more oxygen from getting into the solution. Hence the idea of keeping it dissolved in a glycol seems appropriate if you need a stock solution.

 

[gainer]

Incidentally, how were the British "Limeys" able to remain scurvy free over long voyages? How were the limes preserved?

 

[john_s]

Incidentally, how were the British "Limeys" able to remain scurvy free over long voyages? How were the limes preserved?

Long before, didn't the Vikings eat sprouted grain on their long voyages to prevent vit-C deficiency? Dry (unsprouted) grain keeps very well (years). Sprouting takes a week or two, I would guess.

Ryuji Suzuki says somewhere that ascorbic acid in a developer keeps better in alkaline conditions (the opposite of other dev agents).

 

[sun of sand]

I mixed up 2 Xtol packs when I first bought some late January/February 06
My first developer
Bought water from store ..not well water

Kept most of one in a large Bud bottle (like 3/4 gallon) with saran wrap and cap
Rest into Dasani bottles
Other pack of Xtol into 40 oz bottles/corked Southern Comfort bottles that I found and cleaned and also Dasani bottles

Stored in a room that sees no light and has a small staircase leading to the first floor that isn't used/heated

Used it mostly 1:2 and reused for a bit.

I'm now using the Xtol in that large Bud bottle and it's fine.
I'm actually developing RC prints with it Straight dilution for 2 minutes+- until I get my Dektol
To me it looks pretty good on the prints.


I see no Xtol sudden death syndrome. ?

 

[dancqu]

Recently I was watching a PBS Nova program on the
Franklin expedition to the Northwest Passage. The
members of the expedition got stuck.

Thanks to Global Warming the Northwest Passage for the
first time in recorded history is now open. It will be even
more open as the years go by.

BTW, did they not determine that it was the lead lined
food tins which were to blame? They took ill due to
lead poisoning? Dan

 

[dancqu]

There is also a possibility of other reactions which
actually destroy the compound.

I strongly suspect catalytic induced oxidation is
the cause of XTOL's sudden death. Dan

 

[Tom Hoskinson]

I strongly suspect catalytic induced oxidation is
the cause of XTOL's sudden death. Dan

Could be...
My own direct experience supports Pat Gainer's recommendation. Concentrated ascorbic acid/Ascorbate stock solutions that I mixed in Propylene Glycol or a combination of Triethanolamine and Propylene Glycol have lasted for years.

However, once you mix the stock concentrate with water, the useful life of the resulting solution is short.