fertilizer chemistry question

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silence882

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Hello all,

While reading another post I was reminded of a chemistry question that popped into my head a while back.

I sometimes think about supplementing my MSU-formula fertilizer regime with calcium nitrate and magnesium sulfate. But if I mix the two in the same watering, solubility rules say that calcium sulfate will precipitate. So why doesn't a precipitate form in fertilizer solutions that contain both calcium nitrate and magnesium sulfate? Is there some form of the chemicals that won't lead to precipitation?

And on a barely related note, which chemical is it that turns fertilizers blue-green? I bought 5 pounds of a MSU mix which was whitish until I left it open to the air and the top layer turned blue-green. Is there a hydrate that's white when anhydrous and blue-green when saturated?

My extensive chemistry experience of a single chem 101 class can't answer these questions. Any help would be appreciated.

--Stephen
 
The color is a dye -- nothing in the fertilizer formula itself. We have them use a blue dye for the rain/distilled/RO water formula, and an orange dye for the tap/well water formula.
 
You won't see the precipitates until a very strong concentration at higher ratios of calcium nitrate and magnesium sulfate are mixed into solution.

At the strength used to apply directly to plants the solution is very weak. If you mix a concentrated solution to use with an injector you will see precipitates when you mix a high ration of calcium and magnesium. That is why many high end injectors have two separate mixing heads on one machine.
 
SlipperFan said:
The color is a dye -- nothing in the fertilizer formula itself. We have them use a blue dye for the rain/distilled/RO water formula, and an orange dye for the tap/well water formula.


Oh oh! I came across this tonight while packing.
My blue pure water MSU had turned green. What does that mean?
Anything? Nothing?
 
My MSU that I bought from Ray is red/orangish. And it's for R.O. ??? I need to order more soon as I'm about halfway through. It looks like he's out of the large bag. Who else sells the large 25lb. bags?
 
Heather, yours is growing things.
Stephen, dont worry, the moisture in the air is binding to the dye and making it turn the color of the dye. The MSU in solid form acts as a desiccator, so the dryer the place you keep it, the better.
 
The appearance of the dyes in the fertilizers can be pH dependent, and variations are meaningless as far as nutrition is concerned. The relative moisture content of the powder can affect the pH, so that's why it can change over time.

I don't know if the GreenCare folks change suppliers (probably, to get better pricing), but I have seen their fertilizers in gray, greenish, pale blue or pink, and they all are blue in solution.

The pH things is also to your advantage (with the GreenCare formulas anyway - I can't speak for all brands). If you turn blue when handling the stuff, wiping your skin with household ammonia fades the color quickly.
 
Ray said:
I don't know if the GreenCare folks change suppliers (probably, to get better pricing), but I have seen their fertilizers in gray, greenish, pale blue or pink, and they all are blue in solution.

If you buy wholesale from them, you can ask them to put in any color dye you want. We chose orange (earth-tone) for the tap/well water formula to distinguish it from the rain/distilled/RO version, for which we chose blue (sky-rain).

It all depends on the vendor you get your supply from. Maybe, if the vendor hasn't requested a color, GreenCare has standard dye colors for their different formulas.
 
Last edited by a moderator:
Is it possible to get the stuff without dye? I find it very annoying....but MSU is such great stuff......Take care, Eric
 
I'm sure you can get it without dyes, if you buy enough. For those of us who use proportioners, the dye is a "plus" as it helps you see if the concentrate tank is empty.
 
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