Using magnetic stirrer and Xtol oxidation.

[Radost]

Would a magnetic stirrer oxidizes XTOL enough to reduce development?
Anybody using a magnetic stirrer to mix XTOL?

 

[RalphLambrecht]

Would a magnetic stirrer oxidizes XTOL enough to reduce development?
Anybody using a magnetic stirrer to mix XTOL?

I use a magnetic stirrer to mix all processing chemicals, but I don't turn it up so high. I try to avoid air bubbles.

 

[lamerko]

Definitely not. Xtol contains a large amount of sulfites and sequestrants. In fact, that’s why it dissolves slowly. What can actually kill Xtol is the presence of metal ions - iron and copper. The sequestrants should take care of them, but still… Using tap water is far riskier than using a magnetic stirrer - tap water has a high level of dissolved oxygen, hydrogen compounds, carbonates, and potentially metal ions. Also, tap water can have significant pH variations. If you want peace of mind, just use deionized water.

 

[mshchem]

As long as the vortex doesn't drag in air. I use a prop type mixer, variable speed. Magnetic stirrers in a laboratory setting are used for titration.

There's so much sulfite and other goodies in XTOL even a burly magnetic stirrer can get bogged and bounce the magnet around. Pain.

Low cost easy. Get a genuine Paterson stir paddle, warm your distilled water to 90°F ,add your powder and stir vigorously.

 

[mshchem]

Definitely not. Xtol contains a large amount of sulfites and sequestrants. In fact, that’s why it dissolves slowly. What can actually kill Xtol is the presence of metal ions - iron and copper. The sequestrants should take care of them, but still… Using tap water is far riskier than using a magnetic stirrer - tap water has a high level of dissolved oxygen, hydrogen compounds, carbonates, and potentially metal ions. Also, tap water can have significant pH variations. If you want peace of mind, just use deionized water.

I use a RO system, I fill gallon jugs and let it set for at least 24hrs to let (most) of the air come out, there's a lot of air dissolved in tap water.

You've made very good points here

 

[lamerko]

I've always hated dissolving large amounts of sulfite by hand stirring - it can take 15 minutes of constant stirring. Annoying. With my magnetic stirrer, I choose an appropriate stir bar depending on the beaker and the amount of powder. I always put in the thermometer probe, even though I often turn the heating plate off - the probe creates 'turbulence in the vortex', which makes the stirring more effective. I switch it on and let it stir on its own, while I put something on to watch in the meantime… ever since I got the stirrer, I've 'discovered hot water'

 

[koraks]

As long as the vortex doesn't drag in air.

Even then, the high amount of sulfite will prevent significant oxidation of the ascorbate and phenodine unless you keep mixing it for hours on end.

A magnetic stirrer would be fine for this. I use one all the time when making Instant Mytol.

 

[Don_ih]

I use one all the time when making Instant Mytol.

So do I.

The hotter your water, the less oxygen is dissolved in it. (Thus the bubbles that form on the inside of your water glass as it rises to room temperature.) So, if you're worried, boil it, let it cool, then use it. Even hot water from your hot water tap will have less oxygen dissolved in it than water from your cold water tap.

Interestingly, from the same source as that graph, water more readily dissolves oxygen than it does nitrogen.

 

[lamerko]

If oxygen didn't dissolve easily in water, it would be a problem for a large part of aquatic life…

 

[Don_ih]

If oxygen didn't dissolve easily in water, it would be a problem for a large part of aquatic life…

And they tend not to need the oxygen when they're in boiling water.

 

[runswithsizzers]

RE: Xtol and "metal ions - iron and copper"

At the clinical lab where I worked, the magnetic stirring bars were all encapsulated in plastic. Are there any stir-bars which are bare metal (iron or steel), and if so, would they contribute iron ions to the solution?

And if stirring manually, what about using a stainless steel spoon?

In other words, to avoid taxing the sequestrants, is it a good idea to keep Xtol away from all iron and copper metals?

 

[Alan Johnson]

Google AI:
No, a significant quantity of iron will not dissolve at pH 8 because iron is highly insoluble in alkaline conditions. Instead of dissolving, the stir bar would likely develop a layer of iron oxide or hydroxide (rust), which may flake off as solid particulates. Significant dissolution only occurs if the pH is highly acidic (pH < 4) or if the solution contains chelating agents (like EDTA) that bind to iron ions and pull them into the solution.

 

[lamerko]

And XTol contains a large amount of chelating agents. But in any case, there's no reason for the magnetic stir bar to be bare iron - at least I've never seen one like that. They're all well coated. You still wouldn't want to stir strong acids with such a stirrer, right?

 

[koraks]

Are there any stir-bars which are bare metal (iron or steel)

I've never seen them, but I would not recommend them for photography.