Metol and Sodium Sulphite - Why did it turn black?

[enrico__]

So I get the chemicals to make up some two-bath. My Bath A is Metol

(6g) and Sodium Sulphite(80g). I mix up the Metol first in 100mls of

water. I then mix the Sodium Sulphite in about 300mls of water, and

add to the Metol. I add enough water to make 1 Litre. Everything

looks good until about 2 hrs later when I notice that the mix has

virtually turned very dark brown. It is now black! Why?

 

I hadnt processed any film with it.

 

At what temperature should the water be at when mixing the above

mentioned chemistry? Thats teh only thing I can think of affecting

it. (maybe too warm?).

 

I was using fresh de-mineralised water.

 

Thanks ~enrico

[rowland_mowrey]

Enrico, you sure it is sulfite (SO3) not sulfate (SO4)? That could be one reason.

 

Second, sulfite goes bad over time and turns into sulfate. You can run a poor mans test of sulfite by adding a bit of acid to the sulfite. If you smell sulfur dioxide gas (SO2) coming off, then the sulfite is probably good, but if you smell no or little odor, the sulfite may be bad.

 

Third, I always add the sulfite to the water first rather than the metol. The sulfite scavenges the oxygen.

 

And lastly, a solution like that would be weakly alkaline but the goal in many 2 part developers is to have the part with developer slightly acidic. Shouldn't that be the case here?

 

Ron Mowrey

[michaelging]

This is just a educated guess, but maybe you should have mixed the sodium sulphite first, as it removes the oxygen from the water which reacts with the metol.It seems when I used to mix up my own D72,that I had to mix the SS first. I am sure someone will know the correct answer.

[jim_appleyard]

Doesn't too much sulfite in the water *PREVENT* the metol from dissolving? Recipes that I'm familiar with call for a pinch of sulfite to absorb oxygen in the water, then add the metol, make sure it is dissolved and then the rest of the sulfite.

[neil_miller2]

Most of the developer formulas I've mixed say to mix the chemicals in the order given - except where metol and sulfite are involved. The metol is usually listed before the sulfite. but you are told to add a pinch of sulfite first - to minimise the oxidation of the metol - then add the metol, then the rest of the sulfite.

 

Regards,

Neil

[ole_tjugen]

Metol is difficult to dissolve in an alkaline solution, which is why it's usually recommended to dissolve the metol first (and a pinch of sulfite). But it doesn't really matter, if you can be bothered to stir for long enough or use a magnetic stirrer.

 

If the mix has turned black, it's oxidised. That again means there's not enough sulfite in it, and theonly way to do that is to use something else than sulfite. Your metol is fine, your sulfite is dead.

[michael_gudzinowicz1]

Enrico:

 

With respect to temperature, you should not have problems below 90F or 32C, however, I'd recommend room temperature. Completely dissolve the metol in 800ml water (you can add a pinch of sulfite, but it doesn't really matter), then dissolve the sulfite, and add water to 1L. The composition isn't that different from D-23, and should last a year in a sealed glass bottle.

 

The fact that the solution turned black suggests that you may have used something other than sulfite to make up the solution... sodium sulfide or sodium carbonate will lead to that result. So check your chemical's labels, and reply if you discover what led to the problem.

[enrico__]

Thanks to all so far. In a couple of hours I'll get back to the darkroom and I am going to go mix up another batch with the above advice at hand. I will post back here when Im done...

[enrico__]

Ok, I just mixed up some more. So far so good. Colour is stable, ie a very faint pink. I didnt process any film in it yet. Its in amber glass bottles. Im going to let it sit until tomorrow and then check back.

 

-e.

[chris_waller]

The water should be around 45-50 C. Dissolve a pinch of sulphite in the water first, then add the metol, then the balance of the sulphite. The pink colouration should practically dissappear.

[enrico__]

..well Day 3 in the Two Bath and once again the bastard Bath A has turned dark brown. I decided to dissolve some of the Sodium Sulphite first in 700mls of room temp (26 deg) water, dissolved, then I added the Metol, dissolved, then the remaining sulphite, dissolved and then the remaining water.

 

Im losing patience. Its always teh simple procedures that have to turn out so trivial.

 

Now What??

[profhlynnjones]

Metol won't dissolve in Sod. Sulfite solution, this was always covered years ago when we mixed our own chemicals. Because sulfite is an anti oxidant it is nice to have just a bit of it in the solution. However the available oxygen in the water will cause some odidation of the of the metol, so when I was in Med. Photo School in the mid 50's the printed instructions would say (for a liter or quart) start with a something over half the volume of water, add a pinch of sulfite (maybe a quarter of a teaspoon) and dissolve it. After that, dissolve the Metol. When fully dissolved add the remainder of the Sulfite and dissolve it. You should have no problem after that.

 

I have mixed hundreds of batches of D76, D23, D 25 etc. in small quantities. When I was GM of a pro motion picture lab, I mixed hundreds of of 100 gallon mixes of b/w and color chemicals with not problem.

 

I'm concerned with your situation. This is a really unusual problem that you have outlined. I'm having difficulty trying to understand what is going on.

 

Lynn

[jim_appleyard]

Enrico, what color is your metol?

[enrico__]

Lynn, Jim

 

Im going to try mix another batch again soon. Im going to do it with tap water and again with de-mineralised. I will post my results.

 

Jim, the color of my metol is a faint pink/vague mauve.

 

-e.

[jim_appleyard]

Enrico, it might just be that your metol is oxidized. Metol should be white when new.

[profhlynnjones]

Jim is right!

 

Also, the first thing that the instructions always say is, Don't Use Distilled, Demineralized, or dionized water, it screws up the developer. The only such waters that I recommend are for wetting agent which often flocculates as well as making it easier to grow algae in tap water.

 

Metol should be a neutral colorless crystalline substance.

 

Lynn

[enrico__]

hmmm... I will be in touch with my supplier shortly.

[eugen_mezei]

On 12/9/2005 at 4:55 PM, profhlynnjones said:

Also, the first thing that the instructions always say is, Don't Use Distilled, Demineralized, or dionized water, it screws up the developer.

I wonder what instruction that is. Never heard about distilled water being forbidden for developer.

[David Lindquist]

H. Lynn Jones died in 2012. I'm afraid he was known at times to put out mis-information. See: https://www.galerie-photo.com/ilex-lenses.html

Read not only the opening paragraphs but also the information at the end about the Ilex 20" f/7 Acutar.

 

David