Quote Originally Posted by albada View Post
So I'm thinking I'll follow Alan's idea and say "if your tap water is hard, use distilled water" and ignore chelation because it won't be an issue for this one-shot brew.
If you still have space left in your instruction manual, you can add the line "and those whiners, for whom distilled water is completely unavailable for whatever obscure reasons, are encouraged to boil their hard tap water before using it to mix developer".

Boiling water drives out CO2, which in turn reduces the amount of HCO3- while leaving CO32-, which leads to precipitation of CaCO3, as frequently observed in water heaters of all kind.
Quote Originally Posted by albada View Post
* Citric acid chelates Fe(III) well, and Fe(II) poorly.
* Salicylic acid chelates Fe(II) well and Fe(III) mediocrely (if that's a word).

Could both be used and get good chelation of all iron? These acids have the advantage of being widely available.
If you look at the numbers, you'll see that Salicylic chelates FeII better than Citrate (6.55 vs. 3.2), and it also chelates FeIII better than Citrate (16.35 vs. 11.85). If you have Salicylic Acid in your dev, you won't need Citric Acid any more. Note that chelate stability does not tell the whole story since EDTA, which is a strong chelating agent for both FeII and FeIII, is known to accelerate the Fenton reaction.

Note that Salicylic Acid is not overly soluble (Wikipedia says 2g/l), so you may have to add some other acid anyway to get the pH you want. At 1g/l is is said to keep DS-10 stable, a developer you might remember