Would sodium ascorbate be capable of reducing potassium dichromate?

[What About Bob]

Would sodium ascorbate be capable of reducing potassium dichromate, like ascorbic acid would be? I was reading chromium documents online that mentioned sodium sulfite could be used but from what I have read that ascorbic acid might be more ideal to use?

I have been all around town and nobody sells ascorbic acid powder. One pharmacist looked at me like I was weird. He told me that he loads powder into capsules but doesn't sell powder to anybody.

It looks like I will have to order some if it is needed. Also does it matter on the grade of ascorbic acid powder? I can get it at Artcraft or Amazon under the Nutricost label, which would be cheaper by a good half, which is just ascorbic acid and nothing else.

Thanks

 

[pentaxuser]

I am no chemist as may be clear from what I am going to say and may also indicate I have misunderstood your question but as far as I know Sodium Ascorbate and Ascorbic acid powder are not the same things

However I am amazed that pharmacists or chemists as they are know to us in the U.K do not sell what is vitamin C powder but as I say I may have completely failed to understand your post

pentaxuser

 

[What About Bob]

The dichromate would be reduced, after film processing, from its hexavalent state to a trivalent state which would be less toxic. Ascorbic acid and sodium sulfite were indicated in my research as the agents for use in this chemical reaction and I am looking to see if ascorbic acid would be more beneficial than sulfite for this reaction.

Right now I only have sodium ascorbate on hand. I bought it some time ago to make a developer recipe but never got around to doing so. The ascorbate is a NOW brand. That may not be compatible with what I am setting out to do so I might have to end up buying ascorbic acid.

 

[pentaxuser]

Thanks for the reply,What About Bob. As I said I am lost by the chemistry involved . It was the fact that a pharmacist should look at you as if you were weird that drew my attention. Ascorbic acid is on sale at our larger chemist outlets and unless you were asking for a massive amount of the stuff which might cause puzzlement but not be viewed as concern it just seemed a strange reaction

If it is any help Andrew O Neill uses it to neutralise something in his video on, I think, Carbon printing and it may be potassium dichromate. From what I remember the amount was not massive

pentaxuser

 

[What About Bob]

Yeah he gave me a funny and surprised look when I asked about it. I guess no one has ever asked him such a question before. If he loads them into capsules then that means he has the powder. Why not just sell me a small amount of it? I guess pharmacists do not sell the stand-alone powdered ascorbic acid to consumers without a script? It's a vitamin "scratching head"

I'll give Andrew a buzz. The amount of potassium dichromate that I would be using is probably small as well, 9.5 grams per liter.

Thanks, pentaxuser.

 

[Andrew O'Neill]

I'm not a chemist by any means... but from what I understand, Sodium Ascorbate will neutralise dichromates.

 

[What About Bob]

Thanks, Andrew.

I haven't even opened the ascorbate bottle up yet. I bought it last year after watching one of John Finch's videos on FX-55 but didn't get around to mixing the recipe up.

 

[fgorga]

I am a (retired) chemist...

for this application [i.e. the conversion Cr(VI) to Cr(III)] either ascorbic acid or its sodium salt will work just fine. The salt is more soluble in water and a bit more reactive that the acid form but I doubt that the differences make a difference in this application.

Either form will be oxidized by the Cr(VI) converting the metal to CR(III) and the organic compound to dehydroascorbic acid.

Structures below for those who are interested.

 

[Andrew O'Neill]

Thank you, fgorga, for confirming this.

 

[What About Bob]

I am a (retired) chemist...

for this application [i.e. the conversion Cr(VI) to Cr(III)] either ascorbic acid or its sodium salt will work just fine. The salt is more soluble in water and a bit more reactive that the acid form but I doubt that the differences make a difference in this application.

Either form will be oxidized by the Cr(VI) converting the metal to CR(III) and the organic compound to dehydroascorbic acid.

Structures below for those who are interested.

View attachment 400841

Thank you, fgorga!

The structures look similar with exception of the missing bottom "H" where the sodium is. I would like to learn more about chemistry.

This is great!

 

[fgorga]

Thank you, fgorga!

The structures look similar with exception of the missing bottom "H" where the sodium is. I would like to learn more about chemistry.

This is great!

Bob,

You are quite welcome.

With regard to learning more chemistry and noting your location, I venture to say that there are a number of institutions of higher learning in your neck of the woods that offer 'general chemistry' courses and which, I am quite sure, would let you enroll for a 'small' fee!!!!

Regards for not too far away (the Monadnock region of NH)!

 

[koraks]

I was reading chromium documents online that mentioned sodium sulfite could be used but from what I have read that ascorbic acid might be more ideal to use?

I always use bisulfite. Many things can be used here; I just always went with whatever I had on hand and/or was cheapest. Ascorbic acid or ascorbate have as an advantage that the conversion is entirely odorless. Bisulfite when used to reduce Cr(VI) releases a small amount of sulfur dioxide. With the typical quantities used in a home photographic darkroom, this is far too little to be of a concern and can even go unnoticed altogether, depending on how acute your sense of smell is. However, some people find it bothersome or worry about it, in which case they may prefer to use ascorbic acid or ascorbate. Bisulfite is a little quicker, but ascorbate also doesn't take particularly long to get the job done.

 

[Carnie Bob]

No chemist here but I do use Ammonium dichromate for my gum printing , I am interested in understanding how to neutralize AD in the water bath after printing.?

 

[Andrew O'Neill]

No chemist here but I do use Ammonium dichromate for my gum printing , I am interested in understanding how to neutralize AD in the water bath after printing.?

Bob, recently I've been using for every gram of dichromate, I use twice that of Ascorbic Acid.

 

[Rudeofus]

From a redox potential standpoint Sodium Ascorbate by itself is even a stronger reducer than Ascorbic Acid due to its higher pH, but this higher pH could also be a detriment: there's a chance, that the alkaline environment creates some insoluble chromium III compound. If Sodium Sulfite is indeed the common way to reduce chromium VII, then Sodium Ascorbate should work just as well. If Sodium Bisulfite is more commonly used, then maybe mix your Sodium Ascorbate with some white vinegar before you use it.

 

[koraks]

how to neutralize AD in the water bath after printing.?

A spoonful of ascorbic acid of bisulfite will do the trick. You can stir it into the tray, agitate a minute and you're done.

 

[pentaxuser]

Yeah he gave me a funny and surprised look when I asked about it. I guess no one has ever asked him such a question before. If he loads them into capsules then that means he has the powder. Why not just sell me a small amount of it? I guess pharmacists do not sell the stand-alone powdered ascorbic acid to consumers without a script? It's a vitamin "scratching head"

I'll give Andrew a buzz. The amount of potassium dichromate that I would be using is probably small as well, 9.5 grams per liter.

Thanks, pentaxuser.

Maybe just a different view on Ascorbic Acid between our 2 countries. Asking for it wouldn't cause as much as an eyebrow to be raised here in the U.K.

pentaxuser

 

[MattKing]

Maybe just a different view on Ascorbic Acid between our 2 countries. Asking for it wouldn't cause as much as an eyebrow to be raised here in the U.K.

pentaxuser

Or quite possibly, a difference in the market realities for pharmacies between the two countries.
Around here, very, very few pharmacies are compounding pharmacies. And Ascorbic acid may be obtainable from other sorts of retailers.

 

[What About Bob]

I have sodium metabisulfite. I have loads of sodium sulfite and about two pounds of sodium bisulfate. Looks like I don't have sodium bisulfite.

 

[revdoc]

In this situation, sodium bisulfite is functionally the same as sodium metabisulfite. There's a subtle technical difference that a chemist could explain, but once it's dissolved you have a solution of bisulfite ions, regardless of which you start with.

 

[koraks]

I have sodium metabisulfite

When dissolved in water, this will yield bisulfite This will work to reduce Cr(VI) to Cr(III).

Sodium metabisulfite - Wikipedia

en.wikipedia.org

Saves you a trip to the shop!

 

[What About Bob]

Thanks, revdoc and koraks!