CDS 12000

Charlotte: I don't think the ClO₂ loss in the air space is significant. Let's make simple calculation. Let's consider very small amount of 3000 ppm CDS in 1 liter bottle, so that there is free volume 1 liter of air saturated with CD. Content of the CD (from the table in my pdf) is 4.6 % (volume %) so it's volume is 0.046 liter. There is a rule that one mole of a gas has volume approximately 22,4 liter at normal temperature and pressure. Molecular weight of CD is 67.45 grams. So the mass of 0.046 liter is 0.046x67.45/22.4 = 0.14 g. One liter of 3000 ppm CDS has 3 grams of CD. The loss of CD is about 4.7.%. Of course the overall loss will be greater a lot as some CD escapes from the bottle, but to my mind it is still negligible. There is much more uncertainty at measuring concentration with strips. The calculation is valid for 25 °C. For CDS stored in fridge the loss will be a little bit less. This percentage loss doesn't depend on volume of the bottles or its number.

But from the point of safety the situation is completely different, especially for strong CDS solutions. Let's compare e.g. 1 liter bottle full of CDS with the same amount divided in ten small bottles. There will be 1 liter of air saturated with CD or 0.1 liter* respectively at the end. In the case of an accident the consequences will be quite different – in the blast intensity and the amount of chlorine dioxide gas that is released to atmosphere from the liquid.
* I suppose that every 100 ml bottle will be rinsed with water when it is empty.

So interesting. I had a bottle of 12500ppm CDS in my fridge for some time (over 6 months). It was in a 4 oz PET bottle, and by the time I used it, it had off-gassed somewhat, but was still quite dark, and about 2 oz. Never had a problem with it. Of course, I recognize that I did not do the math, nor, when I ultimately incorporated it into my "mix" of all the various bottles of CDS I had in my fridge, did I test it to see what the ppm actually was. Was the fact that I kept it in the refrigerator all that time significant in this regard?

I realized that Henry's constant and ClO₂ partial pressure are heavily temperature dependent and I made same estimation for lower temperature. If the solution is kept at 5 °C (at fridge), the partial pressure and volume content of ClO₂ in air in the bottle are lower (about one half of these at 25 °C). Consequence is that the critical amount 10 % (v/v) in the air is not overstepped up to CDS concentration circa 13000 ppm. So, there is a good reason to store CDS in fridge, especially the high concentrated one.
Due to lower partial pressure at 5 °C the speed of gas off is also slower - another beneficial of keepinh CDS solution cold.