Stability of ascorbic acid in powder form?

[sanking]

Does anyone know the expected life of ascorbic acid in powder form stored in a partially full plastic bottle?

And would there be any visual signs that it was going bad?

Sandy King

 

[edz]

Does anyone know the expected life of ascorbic acid in powder form stored in a partially full plastic bottle?

Measured in years if its stored dry. The problem is water and/or mositure. Is the acid dry, clump-free and white powder or colourless crystals?

 

[Tom Hoskinson]

Pretty much what edz said, if it is dry L-ascorbic acid with no filler material and is stored in a sealed container.

Here is the JT Baker MSDS: http://www.jtbaker.com/msds/englishhtml/a7608.htm
Vitamin C - L ascorbic acid

 

[sanking]

Measured in years if its stored dry. The problem is water and/or mositure. Is the acid dry, clump-free and white powder or colourless crystals?

It is dry, clump-free and mostly white, with just a few yellow crystals scattered in the powder.

Sandy

 

[john_s]

If the jar is opened frequently, and if the air is somewhat humid, there will be more of the yellowing. I assume that is some kind of deterioration.

I ingest some ascorbic acid every day (deliberately: it's the only developing agent that I eat) and I've noticed this deterioration particularly when I travel in the tropics.

 

[edz]

It is dry, clump-free and mostly white, with just a few yellow crystals scattered in the powder.

Sounds fine. The powder sold in the drugstores sometimes contain a little bit of light yellow crystals. For your uses in developers I'd not give it much more thought.

 

[Gerald Koch]

Ascorbic acid is usually packed under nitrogen but some containers are really not suitable for long term storage once they have been opened. This is particularly true for those with snap type caps. I would suggest transferring to a glass container with a screw cap.

 

[Donald Qualls]

I ingest some ascorbic acid every day (deliberately: it's the only developing agent that I eat) and I've noticed this deterioration particularly when I travel in the tropics.

I routinely ingest enough L-ascorbic acid each day to develop two rolls of film. However, it's not the only developing agent I routinely and intentionally ingest (nor, I'd guess, is that the case for you): I also routinely consume about half a roll worth of caffeic acid, as found in coffee, and a similar capacity of tannic acid as found in tea -- both are developing agents of the staining/tanning type.

If I increase my onion consumption a bit, I might be able to make my blood into a monobath...

 

[sanking]

Ascorbic acid is usually packed under nitrogen but some containers are really not suitable for long term storage once they have been opened. This is particularly true for those with snap type caps. I would suggest transferring to a glass container with a screw cap.

I wonder if virtually all photographic chemicals in poweder form would not also benefit from storage in glass containers?

Sandy King

 

[juan]

I wonder if virtually all photographic chemicals in poweder form would not also benefit from storage in glass containers?

Sandy King

I've wondered the same thing, and I've wondered if Mason jars would work. If kept in a cabinet, they would be away from most sunlight. That leaves the question of whether the coating on the inside of the cap is sufficient to keep the metal from affecting the chemicals. Anyone know?
juan

 

[Gerald Koch]

I've wondered if Mason jars would work.

Yes, I buy chemicals in bulk and transfer them to Mason jars. The jars are very cheap and the caps are designed to hold a vacuum. All in all they work very well. Since they are made of white glass, any developing agents and other light sensitive materials should be stored away from direct light.

 

[Tom Hoskinson]

I've wondered the same thing, and I've wondered if Mason jars would work. If kept in a cabinet, they would be away from most sunlight. That leaves the question of whether the coating on the inside of the cap is sufficient to keep the metal from affecting the chemicals. Anyone know?
juan

My choice is an amber glass Boston Round with a polyseal screw cap.

 

[Gerald Koch]

The coating on the lids is designed to withstand food acids such as those from fruits and tomatoes. Such food can be quit acidic. I have never had any problems with the metal lids rusting. New lids are cheap and they can be replaced each time the jar is reused.

 

[Maine-iac]

Does anyone know the expected life of ascorbic acid in powder form stored in a partially full plastic bottle?

And would there be any visual signs that it was going bad?

Sandy King

Virtually forever. Had a white plastic bottle for about 8 years before using it all up, and it was still cranking along just fine at the end of the bottle.

Larry

 

[craigclu]

Yes, I buy chemicals in bulk and transfer them to Mason jars. The jars are very cheap and the caps are designed to hold a vacuum. All in all they work very well.

Your vacuum comment got me thinking about the food storage systems that pull the atmosphere from mason jars.... I could never quite rationalize one for food after seeing the cost of materials, etc but perhaps for peace of mind with some of the chemicals?

 

[juan]

Your vacuum comment got me thinking about the food storage systems that pull the atmosphere from mason jars.... I could never quite rationalize one for food after seeing the cost of materials, etc but perhaps for peace of mind with some of the chemicals?

I'm no scientist, but over many years of fooling with photography, I've come to the conclusion that there's probably not enough air in a glass bottle or jar to cause significant oxidation. I think the problems folks have come from plastic bottles that allow oxygen to seep in through the bottle itself. I wouldn't think there would be a need for the system. If I'm wrong, I'm sure someone will correct me.
juan

 

[dancqu]

My choice is an amber glass Boston Round with
a polyseal screw cap.

Some may not know that Boston Rounds come clear
and amber, narrow and wide mouth, and they are not
expensive.

BTW, that should be Polyseal. Polycone is another
similar. I'm quite sure both are trade marked names.

I've quite a few and in a range of sizes. Usually
listed in ounces they are actually fractions of a
liter, ie 1/2, 1/4, ... 1/16. Save for the one
ounce which is over size.

For those unfamiliar those caps are a screw cap
with a cork insert; PE likely. Imagine. Dan

 

[albada]

My ascorbic acid started showing signs of weakness after about 2-1/2 months. I estimate it had been opened close to 100 times, as I'm doing much experimentation.

This was the 100 gram version sold by PhotoFormulary.com. It came in a plastic jar about 1/3 full, so there was always plenty of new air in there to degrade the powder.

I think I'll store the new batch in a glass bottle filled with inert gas, and use it to refill a small bottle that's regularly used, which will greatly reduce the number of times the glass bottle will be opened.

There was no discoloration of the powder. It was and still is white.
The symptoms of failure were (1) taking more time to get less density, and (2) not quite as acidic; that is, it required a little less alkali to hit a target pH.
Also, a roll developed two weeks ago made the developer turn orange, which perhaps was due to weak ascorbic acid lacking the capacity to handle a whole roll.

Mark Overton