Bake Calcium Chloride in the oven?

A couple question regarding the recommendation to bake calcium chloride in the oven at 400*F for an hour, in order to ensure that it's anhydrous...

1. Is this still a sound recommendation?
2. Should it cool to room temp before putting in a container?
3. If it must cool, is there any risk in it picking up moisture again from the air?
4. What type of airtight container is recommended? Just the screw top bottle it was purchased in?
5. How long before one should consider doing this again, to maintain calculation assurances?

Thanks!

 

Yes though it is probably easier to make a solution and measure the SG.

No.

Yes and that's why the answer to 2 is "No." This time of year with the heat on and inside humidity low it probably doesn't make much differece.

That should be fine. Run a band of tape around the cap to improve integrity.

If you make solutions over a period of time and check the strength of the powder each time you do so you will get an idea as to how fast a bottle picks up water. It will depend. Do you brew in Antartica or the rain forrest?

 

I make a 10% solution of CaCl using my near-distilled RO water (5ppm). It's easier to measure out and a known solution, as opposed to the 'how much water did my CaCl absorb from the air' guesstimating.

 

I brew in Minnesota. So cold and dry in the winter. Hot and humid in the summer. Sorry for the ignorance about this, but if I do make a solution as you've both suggested, does this solution degrade over time? Or does it remain stable since the CaCl is saturated? Thank you!!

 

It should remain stable since it's a salt solution and can't pick up more moisture than it already has (saturated).

I've been meaning to do this for my own CaCl stock as well. Lately I've just been adding a bit more to the water to account for an unknown amount of moisture in the salt. I concede this isn't great practice, but honestly I don't feel guilty about ballparking a little bit when I'm using RO water to start with. I'm guessing this is probably still more consistent than a lot of people who are anal about measuring yet use a source of water that is variable.

If I did make a hydrous solution, though, I'd be much more capabler at hitting the numbers exactly.

 

It remains stable enough for our uses, as long as it's in a sealed container.

 

The solution is, typically, not saturated though I suppose it could be if you wanted it to be. A solution of CCl2 will exchange water vapor with the air until the chemical potential of water in the solution and in the air is the same. This depends on the concentration of the solution, the temperature and relative humidity. The effect of this change is going to be miniscule if you keep the solution in a closed container.

 

Thanks all. So to confirm, I'm getting that best practice is to create a solution, and continually check its SG when using it, in order to calculate correctly for each brew?

 

Ah, yes, but stable enough for our purpose, correct? Without running some number (which I'm not smart enough to know how to do anyway) I seems as though a solution shouldn't change enough to significantly alter the calculations on a batch of beer. At least, as you say, if it's in a sealed container.

 

Curious... could you combine the processes?

So bake the dry CaCl to drive it back to its anhydrous form. Then immediately dissolve 1000g in 1L distilled water (is that max solubility?).

Could you then have confidence that this solution is 1ml = 1g CaCl2? And use it with that 1:1 ratio? Would this be more stable over time than dry CaCl?

Thanks!

 

Why? You can dissolve it in distilled water and assay it's concentration via hydrometer reading. If I remember right, a 10% solution is 1.090 on a hydrometer. Not necessary to go to the effort of drying it to add water again.

 

Fair enough...

 

booked mark

 

Yes but why bother? Suppose you need 5 grams. Why not dissolve 7 grams of whatever you have in 100 mL of water, check the SG and use the formula to determine how many cc you need to get 5 grams?

Or make a stock solution of say 300 grams in a liter, check its SG and use the stock solution. The drying operation is an un-necessary PITA IMO but if you prefer to do that you certainly can.

No, its less than that depending on temperature (745 g/L at 20 °C).

The problem with saturated or near saturated solutions is that they can become super-saturated if the temperature drops and then drop CaCl2, or not, depending on whether nucleation sites are available etc.

 

AJ, is this still the best formula for that?

g/L = -684.57 + 175.12*SG + 509.45*SG*SG

Thank you!

 

AFAIK it is.