Chemistry question about types (purity) of Sodium Sulfide for sepia toning

Juan Valdenebro · Jan 15, 2022

Hello.
I just found -to my surprise- I can buy locally Sodium Sulfide: it's been impossible for me for years as it can't be ordered online for air shipping, and it can't be brought by friends or relatives coming here either...
But it's the industry standard: it's called 60%.
My questions are: is the PhotoFormulary one 100% pure?
Can the 60% one be used in any way for common sepia toning?
Thanks a lot.

mshchem · Jan 16, 2022

What is quite available here in the USA is liver of sulfur. I understand this to be potassium sulfide, polysulfide. Used extensively in jewelry making to tone silver, copper etc. Sodium sulfide, potassium sulfide, needs to be kept in a glass jar, it stinks so bad it will migrate through ordinary plastic.

It's been decades since I made my own sulfide toner. I suspect that the 60% will work fine. You will need to experiment a bit.

Best Regards Mike

koraks · Jan 16, 2022

mshchem said:
I suspect that the 60% will work fine.

I agree. The nature of the process if toning is such that it isn't very sensitive to contaminants. Just give it a try.

Be careful to store the sulfide in an a absolutely perfectly sealed container; the fumes can fog paper and film!

mshchem · Jan 16, 2022

I found on Wikipedia that the 60% is the most common industry grade, 60 sodium sulfide, the rest is water.

Juan Valdenebro · Jan 16, 2022

Thank you everyone!
Yesterday I emailed photo formulary asking them if what they sell is 60 or 100% pure, but they haven't answered yet.

mshchem · Jan 16, 2022

FYI, the anhydrous form is very hygroscopic. Absorbs water. If you have a formula that calls for anhydrous just adjust the quantity to account for the water.

Juan Valdenebro · Jan 16, 2022

Thank you, mshchem...
Strange no one says they've used the 60% one, and no one says if photo formulary's one is 100% pure...
Possibly later.

mshchem · Jan 16, 2022

Juan Valdenebro said:
Thank you, mshchem...
Strange no one says they've used the 60% one, and no one says if photo formulary's one is 100% pure...
Possibly later.

On B+H website it shows the Photographer Formulary product is the nonahydrate Na2S•9H2O

https://www.bhphotovideo.com/c/prod...Formulary_10_1330_30G_Sodium_Sulfide_30g.html

This is the most stable, kinda makes sense.

This is news to me. I haven't made sulfide toners from scratch in close to 30 years. Stinks but it works well.

Juan Valdenebro · Jan 16, 2022

That's good info, thank you!

Juan Valdenebro · Jan 16, 2022

The 60% industrial grade one, is often named nonahydrate too, so I guess it can be used for sepia toning.

mshchem · Jan 16, 2022

Juan Valdenebro said:
The 60% industrial grade one, is often named nonahydrate too, so I guess it can be used for sepia toning.

60% is roughly 3 H2O according to the all knowing internet.

Molecular weight of anhydrous sodium sulfide is 78. Water is 18 . Na2S•3H2O is 132,

132×0.6 = 79 roughly the most of sodium sulfide.

This has got me going crazy, I'm going to get out some of my ancient Kodak books, try to understand this . Kodak made the finest photo chemicals on earth back pre-1960's. They had the best vendors, made a lot themselves. Had their own paper mills, Kodak Tennessee, now Eastman Chemicals made all manner of things.. The good old days.

Juan Valdenebro · Jan 16, 2022

It seems you're very right... Right now after a quick search I couldn't find the site where I thought after reading 60% was nona...
But yes, wiki talks about 60 being 3 instead of 9, as you just said... Thanks.
Possibly someone comes later and talks about if 3H2O instead of PF's 9H2O would make a huge difference as for making the common 60 3 unusable for sepia toning.

Juan Valdenebro · Jan 16, 2022

I wouldn't have imagined different types of 60% sodium sulfides.
Lucky Chemists knowing so many useful things!

mshchem · Jan 16, 2022

I checked my old Kodak books. The formulas call for Kodak Sodium Sulfide, we may never know what state it was.

Maris · Jan 16, 2022

The chemistry of "sodium sulfide" is complex, unstable and in practice not reducible to precise stoichiometry.

The pure forms Na2S and Na2S.9H2O are white solids but in my years of analytical chemistry I have rarely seen them. The usual appearance becomes yellowish lumps indicating the formation of some sodium polysufide which is a variable composition referred to as Na2Sx where x = 2,3,4, or 5 in different and unpredictable proportions.

Commercial sodium sulfide is called 60% and has the nominal formula Na2S.xH2O where x is about 3 but can vary a bit. This stuff is mainly used for de-hairing hides in a tannery so a precise formula is not required.

Sepia toning using sulfides has been done for more than 100 years without any special study of the toxic, corrosive, and smelly chemistry involved. In practice the amount of sulfide ion in toner is in gross excess compared to the amount of silver it has to convert to sepia coloured silver sulfide. The rotten egg smell associated with sulfide toning is H2S and is more poisonous than hydrogen cyanide HCN. When I do sulfide toning I do it outdoors with a breeze at my back.

Juan Valdenebro · Jan 16, 2022

I'll have to try and see.
Thanks!

mshchem · Jan 16, 2022

Maris said:
The chemistry of "sodium sulfide" is complex, unstable and in practice not reducible to precise stoichiometry.

The pure forms Na2S and Na2S.9H2O are white solids but in my years of analytical chemistry I have rarely seen them. The usual appearance becomes yellowish lumps indicating the formation of some sodium polysufide which is a variable composition referred to as Na2Sx where x = 2,3,4, or 5 in different and unpredictable proportions.

Commercial sodium sulfide is called 60% and has the nominal formula Na2S.xH2O where x is about 3 but can vary a bit. This stuff is mainly used for de-hairing hides in a tannery so a precise formula is not required.

Sepia toning using sulfides has been done for more than 100 years without any special study of the toxic, corrosive, and smelly chemistry involved. In practice the amount of sulfide ion in toner is in gross excess compared to the amount of silver it has to convert to sepia coloured silver sulfide. The rotten egg smell associated with sulfide toning is H2S and is more poisonous than hydrogen cyanide HCN. When I do sulfide toning I do it outdoors with a breeze at my back.

I suspect that what Photographer Formulary carries, the nonahydrate, is what Kodak sold way back in the day, and what was sold as Kodak Sepia Toner in the little plastic pouches up till a few years ago. This doesn't smell or seep through the plastic pouch, all though the sulfide bath does still stink.
The anhydrous or the crude commercial 60% stuff would be pretty difficult to manage. I was would want a fume hood. The last I fiddled with sepia toner, to any extent, was in the late 1980's. I used Kodak Polytoner back in the day, selenium and direct sulfide combined. My wife is a artist, when she's using liver of sulfur, it's pretty bad.
The ammonia odor of selenium toner is noxious but not as bad as sulfide stuff.

Juan Valdenebro · Jan 16, 2022

mshchem said:
... the crude commercial 60% stuff would be pretty difficult to manage.

Any future ideas on how you would replace the nona one with the industrial 60 one in sulfide toning formulas, would be of help... Thank you!

mshchem · Jan 16, 2022

Juan Valdenebro said:
Any future ideas on how you would replace the nona one with the industrial 60 one in sulfide toning formulas, would be of help... Thank you!

First of all 100 grams of the 60% would probably last a lifetime. It would be simple matter of using less of the 60%. Whatever you do start outside with fresh air. As this stuff is nasty and hydrogen sulfide is toxic as mentioned by Maris.
I would use a little less than half of what is called for in the formula

Juan Valdenebro · Jan 16, 2022

OK... Do we agree the 60% nona is what we're supposed to use in formulas?

Juan Valdenebro · Jan 16, 2022

Well, from my very very poor Chemistry understanding, I imagine even if both are 60%, the 9H2O has -in a way I don't really understand- more presence of water than the more common 60% that's 3H2O, which because of its lower water presence is some way more active than the nona one, so that's why you recommend using a bit less than the half, to start tests...

RalphLambrecht · Jan 17, 2022

mshchem said:
What is quite available here in the USA is liver of sulfur. I understand this to be potassium sulfide, polysulfide. Used extensively in jewelry making to tone silver, copper etc. Sodium sulfide, potassium sulfide, needs to be kept in a glass jar, it stinks so bad it will migrate through ordinary plastic.
As an alternative for direct sulphide toning, I found something in Asian food stores called black salt.
It's been decades since I made my own sulfide toner. I suspect that the 60% will work fine. You will need to experiment a bit.

Best Regards Mike

Raghu Kuvempunagar · Jan 17, 2022

RalphLambrecht said:
As an alternative for direct sulphide toning, I found something in Asian food stores called black salt.

@RalphLambrecht: I've been avoiding using Sulfides due to smell, toxicity and fogging scares. Black salt is a more attractive alternative if it does work. Can you give more details of your black salt based toning process?

mshchem · Jan 17, 2022

Juan Valdenebro said:
OK... Do we agree the 60% nona is what we're supposed to use in formulas?

The nonahydrate is only 32.5% sodium sulfide (anhydrous) so if a formula call for 10 grams of the nonahydrate you would need to use 5.4 grams of the trihydrate (your 60% material)

As the nonahydrate has 54% as much sodium sulfide(anhydrous) as the 60% sodium sulfide

Whatever is called out to add of the nonahydrate, take that weight and multiply by 0.54 this should give you how much of the 60% to use.

markbau · Jan 17, 2022

I haven’t used sulphide since I discovered thiocarbamide. I wouldn’t have sulphide anywhere near my darkroom, disgusting stuff.

Chemistry question about types (purity) of Sodium Sulfide for sepia toning

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