[Lewis Thomson (OP)]

Paul has sent The Naked Scientists this question.

"I dabble in hydroponics and am having issues with my calcium nitrate.
I am aware that it is hygroscopic and I feel that my supply has been partial affected (some discolouration and that it was sent through post double bagged (plastic) and I was probably not as careful as I should have been when I first got it). My concern is that this may change the amount of CaNo3 that I am getting when measuring it out by weight - is that a thing.
If so (and it has been affected) how can I -
      a) determine that it is in fact affected
      b) correctly obtain the right amount of pure CaNO3 for my nutrient solutions

Would dissolving the full amount (say 1Kg) in a given amount of water (ppm known) and them testing the ppm after it is in an aqueous solution to then calculate the correct amount of calcium nitrate for my nutrient and if so would the solution be stable for storage."

Discuss in the comments below...

[chiralSPO]

Yes, I think keeping a solution of calcium nitrate in a sealed bottle might be more reproducible than a deliquiescent solid/goo in a bag.

There are a few different ways of determining the true concentration of dissolved calcium, depending on how precise it needs to be.

You can add sodium sulfate to precipitate out the calcium sulfate, which can be filtered, dried, and massed.

You can determine the density of the solution (if you know that the solution only contains water and calcium nitrate, and the concentration is fairly high)

You can determine the freezing point (or boiling point) of the solution (if you know that the solution only contains water and calcium nitrate, and the concentration is fairly low)

You could do a colorometric titration using EDTA and the Patton-Reeder indicator (https://www.canterbury.ac.nz/media/documents/science-outreach/calcium.pdf
https://en.wikipedia.org/wiki/Calconcarboxylic_acid)

[wolfekeeper]

Dunno, can it be dried off in an oven?

[chiralSPO]

And from another product info sheet, not the same product as the above msds.

DENTURANTS
Denatonium benzoate Bittrex 6.6 ppm
Methyl isobutyl ketone 0.25
Fluorescein sodium salt 1 ppm

Is there a question here? Is it related to the thread? I am confused...