Sodium Sulfite (dessicated) shelf life

First - what is dessicated? I found a jar in a box in my dad's basement. Probably 20 years old. If it is any good, what are the instructions / recipe for making a 10% solution and what is it used for? I saw another post that was way over my head...I never took chemistry...about anhydrous etc...so I have no clue.

I also read on http://wynnwhitephoto.com/toning.html about using sodium sulfite to stop the toning process so it doesn't turn pink. I was wondering if there was a particular type of ss to use for this. This is what I was thinking of using it for.

Any ideas?

Thanks,

Dorothy

des·ic·cate Pronunciation (dsdestct
v.vades·ic·cat·ed, des·ic·cat·ing, desinc·cates
v.tr.
1.vaTdrdry out thoroughly.
2. To preserve (foods) by removing the moisture. See Synonyms at dry.
3. To make dry, dull, or lifeless.
v.intr.
vao become dry; dry out.
adj. also adjt)
Lackctg spirit or animation; arid: "There was only the sun-bruised and desiccate feeling in his mind" J.R. SalamJOnHRa.Salamanca dsiccre, ddsiccre: dsicct- + daiccre, tosiccrep (from siccus, dry).]
desic·catidesc
desic·naativdesc. cativecadjtor desc caterana
10grams mixed in 100 ml of solution will make a 10% solution

Sod sulfite is the main ingredient of some hypo clearing agents. I use a couple of tea spoons of sod sulfite in water for this purpose for about 5 minutes.

lee\c

perhaps I should re-phrase this:

how many grams of sod sulfite are needed per how many ml and/or liters water to make a 10% solution?

100 grams in 1000 of water

100 grams of sodium sulfite dissolved in 1 liter of water is a 10% solution.

20 grams of sodium sulfite dissolved in 1 liter of water is a 2% solution - at that strength it is a good Hypo Clearing Agent bath.

Sodium Sulfite is used in developers both as a preservative and as a activating agent.

sorry Dorothy spell check screwed up the verbage and I missed it.

I corrected it now.

lee\c

djkloss said:

First - what is dessicated?
Thanks,

Dorothy

Click to expand...

Dorothy,

anhydrous = no water

dessicated = no water

if enough water is added to sodium sulfite it will eventually dissassociate and form sodium sulfate.

If your sodium sulfite was stored in a tightly closed jar it should have a long shelf life.

In addition to what's been stated above, anhydrous sodium sulfite will slowly absorb water from the air to become crystalline sodium sulfite. This form can still be used for photographic purposes, but you need more of it (by weight) than you'd need of the anhydrous form -- specifically, you need twice as much.

Stored in a tightly sealed glass jar, chances are not much air has gotten in, so not much water could be absorbed. If the jar wasn't very tightly sealed or if the jar or its lid was made of some substance that lets water through (even a little), the sodium sulfite might have absorbed a significant amount of water over 20 years. I really don't know how much might have been absorbed in a worst-case scenario, though. You could try looking at it and see if it looks like a uniform powder (little water absorption) or if there are clumps that look more crystalline (more water absorption). There are other, more reliable, tests to determine the form of sodium sulfite, too, but I don't recall what they are, offhand.

Regarding percentage solutions, you shouldn't just add 100g to 1000ml of water to make a 10% solution (or equivalent for other percentages); you should add 100g to something less than 1000ml (say, 700ml) and then top it up to 1000ml. the reason is that if you add your chemicals to the final target volume of water, the chemicals will take up some volume, so you'll end up with more than the target volume of the solution and slightly less than your target percentage solution. This effect will be very small for small percentages (say, a 0.1% solution), but can be important for larger percentages.

Tom Hoskinson said:

if enough water is added to sodium sulfite it will eventually dissassociate and form sodium sulfate.

Click to expand...

???

Adding water to sodium sulfite will cause it to dissociate to form sodium and sulfite ions. Sodium sulfite whether in solution or as a solid will oxidize to form sodium sulfate.

[QUOTES=Tom Hoskinson]
"100 grams of sodium sulfite dissolved in 1 liter of
water is a 10% solution."

And Ann has said "100 grams in 1000 of water".

The both of you are incorrect. 100 grams in a solution
volume of 1000 ml is correct. How could the two of
you have forgotten "water to make 1.0 liter"
Solvent, solute, solution. Dan

"Sodium Sulfite is used in developers both as a preservative
and as a activating agent."