Fogging redeveloper

[DeletedAcct1]

https://www.freepatentsonline.com/2122599.pdf
Has anyone used benzoin as a fogging redeveloper?
It seems more stable and much less harmful to human than all the other compounds used as such.

 

[Raghu Kuvempunagar]

https://www.freepatentsonline.com/2122599.pdf
Has anyone used benzoin as a fogging redeveloper?
It seems more stable and much less harmful to human than all the other compounds used as such.

Where can you get dioxindol and benzoin sulfonic acid, the two chemicals used in this patent from 1938?

 

[DeletedAcct1]

Where can you get dioxindol and benzoin sulfonic acid, the two chemicals used in this patent from 1938?

Benzoin
https://www.sigmaaldrich.com/catalog/product/aldrich/b8681?lang=it&region=IT
100g 21,9€

 

[Raghu Kuvempunagar]

Benzoin
https://www.sigmaaldrich.com/catalog/product/aldrich/b8681?lang=it&region=IT
100g 21,9€

But none of the formulas in the patent make use of benzoin! Is benzoin the same as benzoin sulfonic acid?

 

[DeletedAcct1]

But none of the formulas in the patent make use of benzoin! Is benzoin the same as benzoin sulfonic acid?

why not?
What's the difference?

 

[Raghu Kuvempunagar]

why not?
What's the difference?

If the benzoin you're talking about is the same as this, then it's molecular formula is C6H5COCH(OH)C6H5. Note that it doesn't have any sulfur in it. All sulfonic acids have sulfur in them thanks to the S(=O)2(OH) group. Hence, benzoin and benzoin sulfonic acid can't be the same chemicals, right?

Plain benzoin is hardly soluble in water: less than 0.3g/l @25C. Typically, the presence of sulfonic acid groups increases solubility (as per Haist volume 1). As substantially more benzoin sulfonic acid (2g/l) is used in the formulas in the patent, you might not be able to substitute it with plain benzoin and get the same level of activity.

Unfortunately, benzoin is sparingly soluble even in organic solvents such as acetone and alcohol. So, that route to get more solubility is also ruled out.

 

[DeletedAcct1]

If the benzoin you're talking about is the same as this, then it's molecular formula is C6H5COCH(OH)C6H5. Note that it doesn't have any sulfur in it. All sulfonic acids have sulfur in them thanks to the S(=O)2(OH) group. Hence, benzoin and benzoin sulfonic acid can't be the same chemicals, right?

Plain benzoin is hardly soluble in water: less than 0.3g/l @25C. Typically, the presence of sulfonic acid groups increases solubility (as per Haist volume 1). As substantially more benzoin sulfonic acid (2g/l) is used in the formulas in the patent, you might not be able to substitute it with plain benzoin and get the same level of activity.

Unfortunately, benzoin is sparingly soluble even in organic solvents such as acetone and alcohol. So, that route to get more solubility is also ruled out.

Benzoin is soluble in alcohol
http://chemister.ru/Database/properties-en.php?dbid=1&id=1551

 

[Raghu Kuvempunagar]

Benzoin is soluble in alcohol
http://chemister.ru/Database/properties-en.php?dbid=1&id=1551

Sparingly soluble. See https://www.x-mol.com/paper/518426 for more information.

In any case, if you go ahead with benzoin for reversal, best luck and do share your experiences.

 

[Rudeofus]

I would like to point out, that the patent in question is 85 years old. If the patent claims an "improved class of fogging agents", it was an improvement over 1935's state of the art. Currently used fogging agents may be much, much better. Benzoine Sulfonate may be more stable than Sodium Dithionite, but could be way less stable than Stannous Chloride in a modern sequestering agent. Remember, that these E-6 kits last a long time, even as working solutions.

If Benzoine Sulfonate is easily available to you, then go try it, but do not expect a miracle breakthrough. Professional photographic companies did read patents, this one surely didn't escape their attention.

 

[Raghu Kuvempunagar]

Benzoine Sulfonate may be more stable than Sodium Dithionite

The instability of dithionite could be a genuine concern for labs which process large volumes of film and can't afford to prepare the solution afresh every time. For low volume shooters who develop at home, dithionite solution can always be prepared at the time of processing and it remains stable for at least an hour. Note that processing in dithionite takes less than five minutes. To find a substitute for dithionite on grounds of its instability is solving a wrong problem.

 

[Rudeofus]

For low volume shooters who develop at home, dithionite solution can always be prepared at the time of processing and it remains stable for at least an hour. Note that processing in dithionite takes less than five minutes. To find a substitute for dithionite on grounds of its instability is solving a wrong problem.

99% of "home shooters, who develop at home" would use a kit, and this kit can not use dithionite, if it lasts less than a year in solution.

 

[Raghu Kuvempunagar]

99% of "home shooters, who develop at home" would use a kit, and this kit can not use dithionite, if it lasts less than a year in solution.

Kits can use whatever they want. Is OP trying to solve kit maker's problem? I thought he was trying to find a fogging redeveloper for his own use.

 

[Rudeofus]

Kits can use whatever they want. Is OP trying to solve kit maker's problem? I thought he was trying to find a fogging redeveloper for his own use.

In this case I strongly recommend dithionite, since this is the most trivially available and cheap fogging agent out there. The patent authors specifically recommend their novel compounds because of their better stability. If you want stability today, use Stannous Chloride in ATMP.