Sodium sulphite V Sodium sulphate

[markbau]

I use Sodium Sulphite in my developers, today I was in a chemical shop and purchased some Sodium Sulphate (I didn't notice that the I was replaced by an A.) I've googled the differences and whilst they say they are slightly different, I'm wondering if it's not much more than a different spelling and my google results didn't mention them as far as photo use goes. So what is the difference as far as mixing developers go? Are they the same or similar?
Thanks for any help.

 

[grain elevator]

Not similar in the least.

 

[Ian Grant]

Sodium Sulphate is used only in Tropical developers as it helps prevent the emulsion swelling at higher temperatures, other than that it can be used as a hardener in fixers, Unfortunately it's no use in other developers so back to the shop for Sulphite

Ian

 

[markbau]

OK, thanks, I'll just have to pay closer attention when buying this stuff.

 

[mohmad khatab]

Sodium sulfite is the basic ingredient, and it is an indispensable element.
Sodium sulfate will not help much except in some very few recipes.

 

[glbeas]

If I remember my chemistry right sulfate is what sulfite turns into when it absorbs oxygen, this reaction being what protects your developer from oxidising as fast in formulas that use it for such. Im sure it has other activities but not overly sure how to describe them.

 

[Down Under]

As you are learning, in photo chemistry, two vowels can make a huge difference...

Sodium sulphAte is a key ingredient in sepia toners. If you intend to ever to toning (disclaimer: not recommended, I've done it in the past, never again!), you'll need a few other chemicals.

Sodium suphIte is an important component for developers. If you intend to home brew your own, you'll be using a lot of it (my preferred mix for Adox Borax fine grain developer takes 80 grams/liter and my kitchen-mix Kodak Dektol a similar amount), and you should buy up a big amount as it's usually cheaper bulk-bought. Keeps indefinitely.

You do have accurate scales, I hope. This is essential for mixing your own.

 

[koraks]

Sodium sulphAte is a key ingredient in sepia toners

I haven't come across a sulfate sepia toner formula. Sulfide, yes. Yet another 1 letter difference with sulfite and an entirely different compound!

 

[Down Under]

I haven't come across a sulfate sepia toner formula. Sulfide, yes. Yet another 1 letter difference with sulfite and an entirely different compound!

You are most likely right on this. My reference books and notebooks are packed away after our interstate move last year, so I couldn't check and refresh my weary brain - I've not done any sepia toning for ten years or more, nor do I intend to do any again in this lifetime. All that two bath preparation, bleaching and redeveloping was much too fiddly and messy for me and my results were inconsistent. Sepia toning is very much an art all of its own, and I'm not the right artist for it...

My apologies to all if I've misled anyone on this.

 

[Raghu Kuvempunagar]

Sodium Sulphate is used only in Tropical developers as it helps prevent the emulsion swelling at higher temperatures,

@Ian Grant: can it also be used to "slow down" a developer without reducing its pH or concentration?

 

[markbau]

As you are learning, in photo chemistry, two vowels can make a huge difference...

Sodium sulphAte is a key ingredient in sepia toners. If you intend to ever to toning (disclaimer: not recommended, I've done it in the past, never again!), you'll need a few other chemicals.

Sodium suphIte is an important component for developers. If you intend to home brew your own, you'll be using a lot of it (my preferred mix for Adox Borax fine grain developer takes 80 grams/liter and my kitchen-mix Kodak Dektol a similar amount), and you should buy up a big amount as it's usually cheaper bulk-bought. Keeps indefinitely.

You do have accurate scales, I hope. This is essential for mixing your own.

I usually buy sodium sulphIte in 5kg lots, been mixing my own D76 (and D72) for many years. I just picked up the wrong tin off the shelf and wondered if I could substitute it, it seems I can't so will return it and get Sulph"I"te. No biggie. I mix my own Thio toner, I'm on my second set of scales, lost my great Versalab scales "in the divorce" but have a accurate to .01 gram set of scales from an Australian manufacturer, so I'm all good on the scales front!

 

[markbau]

You are most likely right on this. My reference books and notebooks are packed away after our interstate move last year, so I couldn't check and refresh my weary brain - I've not done any sepia toning for ten years or more, nor do I intend to do any again in this lifetime. All that two bath preparation, bleaching and redeveloping was much too fiddly and messy for me and my results were inconsistent. Sepia toning is very much an art all of its own, and I'm not the right artist for it...

My apologies to all if I've misled anyone on this.

Sepia toning was simple when Kodak still made their sepia toner but most people use Thio now. Another option is a fairly strong Selenium toner on a warm paper, sorta similar results to the old sepia. I never liked hard core sepia, I used to mix a fairly dilute bleach and pulled the print quite early, of course the old papers that toned so beautifully are now gone but the new warmtone papers (Ilford, Bergger)are pretty good.

 

[Ian Grant]

@Ian Grant: can it also be used to "slow down" a developer without reducing its pH or concentration?

Possibly because it will reduce swelling in the emulsion, however comparing two Agfa developers it's hard to know if the slight difference in development time is due to 6g Metol in Agfa 16 the tropical developer rather than 8g Metol in Agfa 15 with no Sulphate. There's also more Bromide in Agfa 16

Agfa 15 FG Cine Developer

Metol 8g
Sodium Sulphite 125g
Sodium Carbonate 12g
Potassium Bromide 1.5g
Water to 1 litre

Process 7-9 minutes 20ºC

Agfa 16 FG Tropical Cine Developer

Metol 6g
Sodium Sulphite 100g
Sodium Carbonate 12g
Sodium Sulphate 40g
Potassium Bromide 3g
Water to 1 litre

8-10 minutes 20ºC, 3-6 minutes 24ºC

The reduction of Sulphite in the second developer will give rise to higher activity but this is offset bu the cut in Metol, the Bromide is increased to suppress base fog at higher temperatures. Sodium Sulphate solution is Neutral pH 7 so should have no impact on the overall developer pH.

Ian

 

[MattKing]

Sepia toning was simple when Kodak still made their sepia toner but most people use Thio now. Another option is a fairly strong Selenium toner on a warm paper, sorta similar results to the old sepia. I never liked hard core sepia, I used to mix a fairly dilute bleach and pulled the print quite early, of course the old papers that toned so beautifully are now gone but the new warmtone papers (Ilford, Bergger)are pretty good.

I do a fair amount of toning, but usually on RC papers - most frequently Ilford Multigrade or Oriental Seagull Multigrade - so my experiences may differ from others.
I still have some of the Kodak Sepia II toner packages, and they work well.
There are replacements out there - Legacy Pro being one choice.
I also do a fair amount of Brown toning, which also works well.
Split Sepia and Selenium can be fun, although the Ilford responds very little to it.
One counter-intuitive thing that I like as well is to tone cold tone Ilford Multigrade RC paper in Sepia - it is quite responsive.
This is scanned from a brown toned postcard on Oriental Seagull (IIRC)

 

[koraks]

Split Sepia and Selenium can be fun

Certainly. I did some small prints on adix mcc112 the other day in a cold tone developer, toned in selenium, then with a direct sepia toner (outdoors!) For some reason I can't get that very nice purple brown split tone with thiourea toner.

 

[runswithsizzers]

<How are -ide, -ate, and -ite given to elements in chemistry?>
<CHEMISTRY: IDE, ITE, & ATE endings>

 

[Raghu Kuvempunagar]

Possibly because it will reduce swelling in the emulsion,

Thanks Ian. I found a post of yours which suggests increased concentration of Sodium Sulphate does increase development time for another cine developer:
https://www.photrio.com/forum/threads/kodak-d-96a.88209/

Kodak Rapid pAmininophenol Cine developer (Crabtree 1918)
...
By adding 10% (100g) of Sodium Sulphate the development time may be increased to 3 minutes.

 

[Ian Grant]

Thanks Ian. I found a post of yours which suggests increased concentration of Sodium Sulphate does increase development time for another cine developer:
https://www.photrio.com/forum/threads/kodak-d-96a.88209/

That's an example of quite a large amount of Sodium Sulphate, in another reference to the same developer it's stated that the development time with 100g/l Sodium Sulphate is half the time of the same developer with 200g'l Sodium Sulphate, the reference is to work by Crabtree in 1917.

It's worth noting the Carbonate pH of the p-Aminophenol based developer differs from the Agfa examples, also that around 1917/18 emulsions were poorly hardened so the effects of Sodium Sulphate would be very significantly grater compared to today's emulsions.

Ian