(Visually) Assessing hydrate form of years-stored alkali?

Hi:

I bought many bulk chemicals years ago & procrastinated my big ‘development’ plans...but hope to get going this year.

I am concerned about the gradual hydration into different crystal forms by some of the chemicals like sodium carbonate, borax, sodium thiosulfate, maybe sodium bicarbonate & lye.

I assume the washing soda & ‘thiosulfate will have gone to decahydrate, and vaguely recall there may be be two distinctly different crystal shapes for the latter (‘rice’ vs. ‘complex?’).

Lye I suppose could just turn to slime...if it did, weighing it meaningfully may be a problem.

The baking soda doesn't seem to change appearance in the kitchen.

Any helpful visual cues from someone who’s been there, done that?

Thank you

Murray

Bake the lot in an oven at 150 C, and make it all anhydrous!

By 'lye' do you mean caustic soda - sodium hydroxide? If so, then it's easier just to bin it and buy fresh. It's cheaply sold in 500gm packs as drain cleaner, and the amount needed in a developer is usually only a few grams at most.

There's also the issue that some chemicals will absorb carbon dioxide from the air and change alkalinity if not properly stored hermetically.

Many soft plastics are porous to gas molecules, and anything stored in such containers should be treated with suspicion.

Where's Ben when you need him?

I agree with Joe-don't try to save the sodium hydroxide-it's gone.

In all honesty, I don't trust visual appearance(aside from color change, as happens with some transition metal salts) to determine the state of hydration aside. It's WAY too subjective, and sometimes dehydrating it doesn't necessarily restore the former appearance.

What I do in the lab if I need to know with certainty is either buy the stuff already in its hydrated form, buy guaranteed anhydrous in small bottles and open them right before use, or just stick it in the oven and dry it at a temperature where I know that it will dehydrate. 150ºC for a few hours won't cause a problem with sodium carbonate.

I wouldn't worry terribly about the sodium thiosulfate.

Thank you both.

I knew there was a reason I kept the toaster oven my wife acquired on Black Friday last year for $10. Unfortunately I forgot what I wanted to do with it and donated it to a charitable organization this summer...

I guess I will start by looking. The CO2 absorption sounds like the largest uncertainty.

Good news, (I guess) is that the only material stored in the garage was the 25# tub of sodium thiosulphate.

Won't be the first time I wasted money trying to save money....

Thank you both.

 

I knew there was a reason I kept the toaster oven my wife acquired on Black Friday last year for $10. Unfortunately I forgot what I wanted to do with it and donated it to a charitable organization this summer...

 

I guess I will start by looking. The CO2 absorption sounds like the largest uncertainty.

 

Good news, (I guess) is that the only material stored in the garage was the 25# tub of sodium thiosulphate.

 

Won't be the first time I wasted money trying to save money....

The sodium thiosulphate will probably still be OK. It's sold as the pentahydrate salt, is very stable and its effectiveness can still be judged simply on an old film leader in case of doubt.