TF-3 alkaline fixer, sodium sulfite solubility

[Shakti V.]

I just mixed a TF-3 fixer. Here is the formula I used:

* Ammonium thiosulfate (57-60%) 800 ml

Sodium Sulfite (anhy) 60 g

** Sodium Metaborate 5 g (50ml of 10%sodium metaborate/L)

Distilled water to make 1000 ml

* To make ammonium thiosulfate: I mixed ammonium chloride 600g + sodium thiosulphate(penta) 1406g [900g for anhy ; divide by 0.64 (900/0.64), to get grams in penta] in 1.5 L of water. I used 800ml only per 1Liter of fixer.

** I made sodium metaborate from Borax 69g + 14.5g NaOH (tech grade,flakes) in 1L of water, for a 10% solution of sodium metaborate (100g/L); I used 50ml to get 5g.

There was a very thin layer of white substances/flakes floating on top of the finished solution. Also, the sodium sulfite (photo grade, in white powder form) was very hard to dissolve. I heated the solution to 50degC before adding sodium metaborate, to help dissolve the sodium sulfite, but still it doesn't dissolve completely. There is still a considerable amount of sodium sulfite at the bottom of the solution up to now. Is this occurence normal for TF-3 fixer?

I notice that the sodium sulfite in this formula is thrice the usual amount per liter, which is normally 15g/L. I assume that that is the reason why the sodium sulfite was incompletely dissolved. What else could I do to dissolve the sodium sulfite? Or should I just let it stand in the solution? Will it harm the fixer?

If you notice any mistakes in the formula or the method, please post the corrections here.

Thanks again to this wonderful forum.

Footnote: I mix ammonium thiosulphate and sodium metaborate from scratch because the chemicals are not available here.
I wouldn't buy ready-made fixer now because I am at a phase where I want to learn to mix my own chemicals.

 

[Ole]

The mistake is that you've mixed ammonium chloride and sodium thiosulfate to get ammonium thiosulfate.

Yes, you can do that - but you have to rememer that you get a lot of "extras" with it: An equal amount of sodium chloride. That sodium isn't removed from the solution, so it contributes to the concentration of sodium sulfite. Something, I don't know what, has gone beyond the saturation limit with the extra sodium.

As soon as we have the "Articles" section back online, look for OF-1 fixer. It's very similar to what you're trying to do, and it works. I confess that I can't remember how I wrote it down - I mix it in "cups", "shot glasses", "teaspoons" and "splashes".

 

[srs5694]

As soon as we have the "Articles" section back online, look for OF-1 fixer. It's very similar to what you're trying to do, and it works. I confess that I can't remember how I wrote it down - I mix it in "cups", "shot glasses", "teaspoons" and "splashes".

I happen to have it in my formula costs spreadsheet:

sodium thiosulfate, crystalline: 220g
sodium sulfite, anhydrous: 30g
ammonium chloride: 40g
sodium metaborate: 20g
water to make: 1l
Dilution: 1+0

There's a note that the sodium metaborate was originally specified as 20cl of a 10% solution. I presumably converted it because I've got (and/or can buy) the chemical in solid form.

I've never used this formula myself, so I can't comment on it beyond providing the formula and saying that the cost is typical, or perhaps a bit low, for sodium thiosulfate-based fixers.

 

[Shakti V.]

I happen to have it in my formula costs spreadsheet:

sodium thiosulfate, crystalline: 220g
sodium sulfite, anhydrous: 30g
ammonium chloride: 40g
sodium metaborate: 20g
water to make: 1l
Dilution: 1+0

There's a note that the sodium metaborate was originally specified as 20cl of a 10% solution. I presumably converted it because I've got (and/or can buy) the chemical in solid form.

I've never used this formula myself, so I can't comment on it beyond providing the formula and saying that the cost is typical, or perhaps a bit low, for sodium thiosulfate-based fixers.

Thank you Ole and srs5694.

OF-1 fixer should be used at full strength, as it is in the directions. I assume sodium thiosulfate here is in penta, coz you wrote 'crystalline'. Am I right? As for the sodium metaborate, if it is 20g in solid form, then it should be 200ml of 10% solution (sodium metaborate 100g/L makes 10%).

You haven't stated the fixing time for film and prints (Resin-coated and fiber based). Please let me know the fixing time. Thanks.

~

As for the TF-3 that I've mixed, I've researched that the sodium chloride doesn't do any harm in fixing, except for the concentration; hence, the insolubility that I experienced. Some photographers who don't have access to ammonium thiosulphate (like me), use the formula that I used (sodium thio + ammonium chloride). The resulting sodium chloride can be removed by gradually evaporating the water, but those who don't do this don't experience any harm with the sodium chloride.

~

Thanks for your help.

 

[Ole]

OF-1 is sort of inbetween sodium and ammonium thiosulfate-based fixers. It is almost as rapid as a full "rapid" - typical clearing times for a film leader is in the 20 seconds range. The chloride seems to speed it up a little, too! I give RC papers 2 minutes, FB paper and films 5 minutes. All I can really say is that this is more than sufficient, I haven't done systematic tests on fixing speed.

Sodium thiosulfate pentahydrate is correct.

The metaborate can be reduced, omitted, or substituted with sodium bicarbonate with very minor effects. I use metaborate when using an acid stop, bicarbonate only when there's no acid involved anywhere (I don't like bubbling solutions). If an acid stop is not used, there's strictly speaking no need for the extra alkalinity of the metaborate so it might just as well be dropped altogether.

 

[nworth]

The mistake is that you've mixed ammonium chloride and sodium thiosulfate to get ammonium thiosulfate.

Yes, you can do that - but you have to rememer that you get a lot of "extras" with it: An equal amount of sodium chloride. That sodium isn't removed from the solution, so it contributes to the concentration of sodium sulfite. Something, I don't know what, has gone beyond the saturation limit with the extra sodium.

...

True. You should also remember that ammonium chloride is an acid, and you will have to adjust the pH accordingly. The order of solution may be important here to determine why the sulfite doesn't dissolve easily. The sulfite is usualy dissolved first. If your sulfite does not dissolve easily in plain water, you may have a bad batch, or your water may be contaminated. Sulfite dissolves somewhat more difficultly in acid, so the ammonium chloride may be having some effect. As for floating material in the final mix, the most likely problem is that you did not fully dissolve each chemical before you added the next. (Contamination is also a possibility.) You really need to get stir crazy, especially if the solution is cool. Using warm water helps, but be sure that every last crystal of each material is gone before adding the next.

Incidently, OF-1 not only works, but it stinks less and (I think) it's superior to TF-3.

 

[Shakti V.]

Luckily, the solution cleared after stirring crazy and letting it sit for several hours. Yes, I added the metaborate before sodium sulfite was fully dissolved, because, well, it can't be dissolved. I think the problems that occurred are also due to higher concentration of TF-3 and because ammonium thiosulphate was made from sodium thiosulphate and ammonium chloride (which as you said is an acid), thereby straining the solubility of sodium sulfite.

Thanks for all your help. I will try OF-1 too. I think it is easier to mix. I will use it for 2 mins. for RC prints, 5 mins. for FB prints, and film.