# Macro Solution Colour



## cbaum86 (14 Dec 2020)

Just a quick question to either put my mind at ease or tell me I'm doing something wrong.

When I mix up the macro solution it's clear in colour as expected. As the weeks go on - the 1L mixture lasts about 12 weeks - it turns a more and more orange/brown colour getting close in colour to the  micro mixture. Is this expected or am I likely getting some contamination from somewhere?

Thanks.


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## GHNelson (14 Dec 2020)

Probably contaminated!
What type of bottle are you using?


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## cbaum86 (14 Dec 2020)

hogan53 said:


> Probably contaminated!
> What type of bottle are you using?


It's an old TNC complete bottle. I washed it out 3 or 4 times before using it but maybe I either didn't do a good enough job or there's something in there that's in the plastic.
I stated using a separate syringe to dose with when I made up a new mix to eliminate that but still get the same result.


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## cbaum86 (14 Dec 2020)

Hmmm, I did have a search before but couldn't find anything. Just came across this Discoloured macro mix . . . and I think I have the same 'issue' which doesn't seem to actually be an issue if I'm reading it correctly. Looks like it could be the ascorbic acid causing the tint over time.


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## GHNelson (14 Dec 2020)

Yea could well be  
Have you tried mixing with Distilled Water....


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## Wookii (14 Dec 2020)

cbaum86 said:


> Hmmm, I did have a search before but couldn't find anything. Just came across this Discoloured macro mix . . . and I think I have the same 'issue' which doesn't seem to actually be an issue if I'm reading it correctly. Looks like it could be the ascorbic acid causing the tint over time.



Yep, that was my thread. When I stopped adding the ascorbic acid, the macro solution remained clear. I've since learnt that there is no real need to add the ascorbic acid to macro mixes, just the micro mixes.


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## hypnogogia (14 Dec 2020)

Wookii said:


> I've since learnt that there is no real need to add the ascorbic acid to macro mixes, just the micro mixes.


I thought you only need ascorbic acid if making an AIO as the phosphates in the macro react with the Iron in the micro when Ph >6.


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## Wookii (14 Dec 2020)

hypnogogia said:


> I thought you only need ascorbic acid if making an AIO as the phosphates in the macro react with the Iron in the micro when Ph >6.


 That's two separate but related issues as I understand it. The concentrated phosphates can react with free non-chelated iron and produce insoluble precipitate. The lower pH is required to stop the minerals (including the iron) from coming out of chelation in the first place, and that latter point is preferential for both AIO mixes and pure micro mixes.


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## hypnogogia (14 Dec 2020)

Wookii said:


> That's two separate but related issues as I understand it. The concentrated phosphates can react with free non-chelated iron and produce insoluble precipitate. The lower pH is required to stop the minerals (including the iron) from coming out of chelation in the first place, and that latter point is preferential for both AIO mixes and pure micro mixes.


I've learnt something new, thank you.


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## Zeus. (14 Dec 2020)

I started adding Ascorbic Acid 1.0g/l and Potassium Sorbate 0.4g/l for its anti mould properties to both Macros and Micros mixes quite some time ago, as I got mould in them both (was making big fert batches at the time)and since I have always added it to both mixes, the rational was if it OK for an AIO mix then its OK for a Macro and Micro mix as well.
My Macro mix changes colour was well but not as brown/dark as the micro mix.
I don't think adding Ascorbic Acid 1.0g/l and Potassium Sorbate 0.4g/l to the Macro mix has any other side effects apart from the colour change, I'm sure 'The half Blood Prince' knows (@X3NiTH )


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## Wookii (14 Dec 2020)

Zeus. said:


> I started adding Ascorbic Acid 1.0g/l and Potassium Sorbate 0.4g/l for its anti mould properties to both Macros and Micros mixes quite some time ago, as I got mould in them both (was making big fert batches at the time)and since I have always added it to both mixes, the rational was if it OK for an AIO mix then its OK for a Macro and Micro mix as well.
> My Macro mix changes colour was well but not as brown/dark as the micro mix.
> I don't think adding Ascorbic Acid 1.0g/l and Potassium Sorbate 0.4g/l to the Macro mix has any other side effects apart from the colour change, I'm sure 'The half Blood Prince' knows (@X3NiTH )


I'd like to know why the macro mix goes brown with the added ascorbic acid too, I never got an answer on my original thread. It must be a chemical reaction of some sort, which is why I now exclude it - purely from not knowing what that reaction that was, combined with reading that making the macro mix acidic provided no benefits.

Agree on the Potassium Sorbate though, I add that to all my mixes as I keep them on the auto-doser for long periods. I've found it a bugger to dissolve though if added with everything else, so I now dissolve it in the RO/DI water first, and then add all the other salts afterwards.


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## cbaum86 (14 Dec 2020)

Zeus. said:


> I started adding Ascorbic Acid 1.0g/l and Potassium Sorbate 0.4g/l for its anti mould properties to both Macros and Micros mixes


Yeah, I'll admit until the 2nd batch I mixed up I had no idea why I was adding either of these. I just used your ferts spreadsheet and I figured if they were on a 476 sheet workbook I wasn't going to question it.
I couldn't care less about the colour change as long as it's expected / non-detrimental.

Although I suppose it is always interesting to know why it's happening. Hopefully you're tag will give us some Jedi-chemical answers.


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## X3NiTH (14 Dec 2020)

The yellow brown tinge is due to the decomposition byproducts of the oxidisation of ascorbic acid.






Erythrulose (non reversible compound of the oxidation reaction) is used in skin tanning products! The oxidation reaction doesn’t only happen in a solution I have seen it with dry powders specifically if I premix and long term store a sachet of my remineralisation mix of dry salts of Potassium Bicarbonate , Calcium Carbonate and Magnesium Carbonate and Ascorbic Acid together in one bag allowed to mingle together, over time the minuscule amount of atmospheric moisture sealed in the tiny zip lock plastic bag turns some of the powder brown (went and looked to see if I had a bag left to show a pic but alas I’ve used all the baggies up).

Storing the resultant fertiliser mix solution in the dark reduces the effect of oxidation as Ascorbic Acid is light sensitive. You can use other acids to reduce the pH of the fertiliser mixture that won’t react in this way discolouring the solution but I wouldn’t recommend a novice attempt this, stick to the Ascorbic Acid it’s a lot safer and easier.


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