Keeping properties of Sodium Sulfite?

[Joshua_G]

I'm about to mix Instant Mytol concentrate in Propylene Glycol – an amount that will last me for few years, may be many years. Now, in this formula, the Sodium Sulfite is mixed separately in water, 60 g/L.

What are the keeping properties of Sodium Sulfite anhydrous powder in a tight closed container, with or without Silica Gel?

What are the keeping properties of Sodium Sulfite mixed in water, 60 g/L, in a partially filled bottle?

Will Sodium Sulfite mixed in water to a greater concentration, say 120 g/L keep better, or worse?

What is the highest recommended concentration of Sodium Sulfite mixed in water?

 

[Lee Shively]

Dry sodium sulfite is pretty much stable and I doubt it would deteriorate to any measurable extent for photo purposes in years and years of storage. As long as it is kept dry, that is.

I don't know about mixed liquid forms of sulfite. Somewhere in my muddled mind, I seem to remember reading that it eventually changes its chemical properties over time. The less chemically challenged will certainly be of help with the answers.

 

[Alan Johnson]

Sodium sulfite solution in a partially full glass bottle will react with the oxygen in the airspace till the oxygen is all gone.There is some evidence that the anaerobic solution does not change much. For instance, here is the MSDS for 5% sodium sulfite solution:
http://www.sciencelab.com/xMSDS-Sodium_Sulfite_5_Solution-9926898
It is described as stable(section 10).

 

[gainer]

I would say first that it is not important to get precise measurement of the sodium sulfite. You could certainly test this idea by doing two experiments with two different amounts of the fresh sulfite solution. If you are satisfied that extreme accuracy is not required, you could then find a volumetric measurement of the amount required for a single batch. You will probably find that a certain number of level teaspoons will be sufficiently accurate. Then you need only keep your dry sulfite stored away from moist air.

 

[Joshua_G]

Dear Gainer,

There is no problem for me to weigh the Sodium Sulfite, as I purchased pretty accurate electronic scale. I'd like to do mixing as little as possible, hence, my question about the keeping properties of Sodium Sulfite. I prefer discarding small amounts every now and than and keeping the solution in small, filled to the brim, bottles. However, I wonder how long will that solution keep? Alternatively, how can I check, before the actual developing, whether the Sodium Sulfite solution is good? May be by measuring the PH? Also, how can I check whether the Sodium Sulfite powder is good? (I have an amount that will last probably to the rest of my life). May be by weighing it?

 

[Photo Engineer]

A filled sealed glass bottle with sodium sulfite solution in distilled (boiled) water with no oxygen, will keep almost forever. The boiling will drive out oxygen and carbon dioxide as much as possible.

A nitrogen purge and blanket will help.

Without these, there will be a dip in sodium sulfite concentration until it uses up the carbon dioxide and oxygen and then it will level off and keep for a long time, years at least as long as it is sealed and filled and in glass with a good cap.

PE

 

[Joshua_G]

A Blanket? What do you mean by blanket (in this context)?

In a filled to the brim bottles – to the best of my understanding, there is no air. Right? So, why the nitrogen purge and blanket?

 

[Photo Engineer]

A nitrogen cover over the solution that has driven off all of the air.

This is a common term in chemistry and wet photography.

Air and especially carbon dioxide and oxygen, are dissolved in any water. Boiling will drive off some, but they redissolve rapidly in the water. Bubbling nitrogen into the water drives off some of the dissolved air and also places a thin layer of nitrogen in any air space left in the bottle.

PE

 

[Joshua_G]

Thanks.

Nitrogen facility is beyond my reach at present – buying every now and than fresh chemicals seems to cost me less …

 

[gainer]

I think you worry too much! The sulfite is not the critical part of that developer. Its oxidation product is sodium sulfate which at worst will slow development, but it has to get pretty strong to do much of that. As PE says, sulfite solutions last a long time. Furthermore, a developer like Mytol can be made without any sulfite if you adjust the pH. Have you tried PC-TEA?

 

[Joshua_G]

Have you tried PC-TEA?

No. What are the benefits and or drawbacks of PC-TEA over Instant Mytol / XTOL?

 

[gainer]

I'll let someone else answer that. A person cannot always see the blemishes on his own children. One advantage is the single stock solution. Another is two active ingredients in triethanolamine solvent. You could as well mix the Phenidone and ascorbic acid in propylene glycol and use a carbonate or metaborate solution as activator.