sodium bisulfite
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The two possible reactions for sodium bisulfite are (1) lose sulfur dioxide and be converted to sodium sulfite or (2) oxidize to form sodium sulfate and sulfur dioxide. Since it is in sealed jars meither of these reactions seems likely.
Seeing old Kodak chemical jars really brings back memories where one would see whole shelves of them in photo stores..
Seeing old Kodak chemical jars really brings back memories where one would see whole shelves of them in photo stores..
Sodium Bisulphite doesn't have a long shelf life, strictly speaking it's a mixture of Sodium Metabisulphite and Bisulphite and has less free SO2. Chances are that Kodak Bisulphite is long decomposedit's not worth using.
Ian
Ian
Wouldn't it be plenty obvious (smell! ) if Metabisulfite lots substantial amounts of its Sulfur Dioxide? Wayne's container looks tightly sealed, and a quantitative release of Sulfur Dioxide would have likely broken the glass or the lid.
It can go off in a tightly sealed bottle, I has a couple of unopened Kodak Sodium Bisulpite bottles and it has decomposes, it should have a very sharp acidic smell, just don't try sniffing it !
You only get quantitative release of Sulphur Dioxide if it's added to an acidic solution not stored in a glass bottle
Ian
Thanks, Ian, if I interpret this correctly, Wayne's bottles are most likely ok then.
Just to add some numbers to the discussion: if one mol of Sodium Metabisulfite (Na2S2O5, mol weight ~ 190g) decomposes, you get 1 mol Sodium Sulfite, and 1 mol Sulfur Dioxide, which equals 64 grams or 22.4l of pure Sulfur Dioxide. This publication claims that 25.27 mg SO2 per m3 air are noticeable, so these 64 grams of SO2 would foul up 2500 m3 of air.
Just to add some numbers to the discussion: if one mol of Sodium Metabisulfite (Na2S2O5, mol weight ~ 190g) decomposes, you get 1 mol Sodium Sulfite, and 1 mol Sulfur Dioxide, which equals 64 grams or 22.4l of pure Sulfur Dioxide. This publication claims that 25.27 mg SO2 per m3 air are noticeable, so these 64 grams of SO2 would foul up 2500 m3 of air.
Yes Wayne's bottles will be OK and in good condition, but most likely not the contents. The seals aren't perfect and over a period of years there's sufficient gas diffusion.
Ian
In order for the bisulfite to decompose three things are needed.
o Heat, the warmer the storage conditions the greater the rate of decomposition.
o Moisture.
o The sulfur dioxide must be able to escape. So it depends of the quality of the seal on the jars.
Hence the admonition to store chemicals in a cool, dry location.
o Heat, the warmer the storage conditions the greater the rate of decomposition.
o Moisture.
o The sulfur dioxide must be able to escape. So it depends of the quality of the seal on the jars.
Hence the admonition to store chemicals in a cool, dry location.
Which has better shelf life - Sodium Bisulfite or Sodium Metabisulfite? Or are they equal in shelf life?
It's really about purity level and the different ways Metabisulphite is made, in Europe compared to the US, JT Baker sell both. I used to buy quite a few 25 Kg bags at a time per month for work. Metabisulphite is much purer and has a far higher free Sulphur Dioxide content .
Shelf life is another issue Metabisulphte will last slightly longer when the formula is for Bisulphite, when the Metabisulphite is in a developer as an anti-oxidant it's criitical it's reasonably fresh - Pyrocat HD for instance. Fresh Metabisulphite and in water Pyrocat HD will last 3 years (Part A).
In Wayne's case with clumping it's collapsed, if it's OK you'll notice the SO2 as soon as you open it if it's OK even at arms length
Ian
You can think of sodium or potassium metabisulfite as a chemical container for sulfur dioxide K2S2O5 or K2SO3.SO2 using dot notation. One of the sulfur atoms is less tightly bound than the other.
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It's really about purity level and the different ways Metabisulphite is made, in Europe compared to the US, JT Baker sell both. I used to buy quite a few 25 Kg bags at a time per month for work. Metabisulphite is much purer and has a far higher free Sulphur Dioxide content .
Shelf life is another issue Metabisulphte will last slightly longer when the formula is for Bisulphite, when the Metabisulphite is in a developer as an anti-oxidant it's criitical it's reasonably fresh - Pyrocat HD for instance. Fresh Metabisulphite and in water Pyrocat HD will last 3 years (Part A).
In Wayne's case with clumping it's collapsed, if it's OK you'll notice the SO2 as soon as you open it if it's OK even at arms length
Ian
I took the cover of my jar of Sodium Metabisulfite and it has a strong, acrid, sharp sulfuric acid type smell. What is it suppose to smell like when goo and what is it suppose to smell like when bad?It's really about purity level and the different ways Metabisulphite is made, in Europe compared to the US, JT Baker sell both. I used to buy quite a few 25 Kg bags at a time per month for work. Metabisulphite is much purer and has a far higher free Sulphur Dioxide content .
Shelf life is another issue Metabisulphte will last slightly longer when the formula is for Bisulphite, when the Metabisulphite is in a developer as an anti-oxidant it's criitical it's reasonably fresh - Pyrocat HD for instance. Fresh Metabisulphite and in water Pyrocat HD will last 3 years (Part A).
In Wayne's case with clumping it's collapsed, if it's OK you'll notice the SO2 as soon as you open it if it's OK even at arms length
Ian
The smell is not going to change only its intensity. If it smells strongly that is a good sign. Had it decomposed the smell would be weaker.
Thanks Gerald, it must be good cause it's plenty strong.
The 2 oz jar of metabisulfite I bought today came from a home brewing supply store that opened less than a year ago, and it has no strong odor. I'm NOT going to shove my nose in it, but wafting it toward my face with my hand (like they taught us in chemistry) produces no noticeable smell and I have a pretty strong sense of smell. Same thing for the opened jar of bisulfite.
It's a different chemical, but I have a bottle of Metol that's well into it's 30s years. I hadn't used it in a couple of decades, and when I opened it up, the surface was slightly browned, but under the surface it was still white. I stirred it up, and it's working fine. In order to oxidize, things have to be exposed to oxygen, and that means, as we all know, agitation. After the initial burst of degradation, no exposure = nothing more happens. I don't know what the chemical process is here, but that may or may not apply.
Everything I'm reading online says bisulfite and metabisulfite smells strongly once mixed with water, releasing SO2, but shouldn't smell that powerful when the powder is fresh. I'm not qualified to argue the point that's just what I'm reading, but I don't ever remember getting a strong odor when working with either in powder form.
I don't remember it(strong odor) either and that's kinda why I ask. It's cheap enough and available locally so that when in doubt - dump!
Sulfur dioxide is one of those chemicals that has a piercing and easily detected odor. Like other chemicals for example ammonia it is easily detected in vary small quantities. So a person's nose is not really adequate to detect concentration accurately.
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