Why CaCl2 is very warm ?

[rthomas]

Tom, I finally managed to get hold of CaCl2, but not CaSO4.

On the pack, it is labeled CALCIUM CHLORIDE anhydrous CaCl2. There is also a warning that say the chemical is corrosive. Molecular weight is 110.99 .

The chemical appear dry. Not 100% powder but most are in the form of lumps. I had to softly hammer it to get it into powder form. Then I scooped 1 tsp and added that into a beaker with some water in it.

I was very surprised that the mixture became very warm !

Is this normal for CaCl2 ? Since it is corrosive, can I safely store in the plastic container and leave it in my tank's cabinet at 32 degree Celsius ?

Please advise. I am very worried indeed

 

[rthomas]

Casualties

I made a 50% WC then filled up my 160g tank. I waited for about 2 hours, then did another 50% WC. At each WC, added anti-chlorine. Neons and SAEs looks good.

I decided to dose CaCl2 at 4 teaspoons. That will give me 10.63 ppm Ca (with Fertilator). I also added 1tsp MgSO4.

After about 4 to 5 hours I noticed strange behavior with my Congo Tetras. They hide at the back of the tank. Neons seems ok for the moment. But I have 2 dead SAEs. And my Chinese Algae Eater darted across the tank for no reason.

During both WCs, I top up the tank slowly and added anti-chlorine as directed. I just do not know what caused this. I would like to blame the CaCl2 but should I ?

 

[rusticitas]

If I recall my chemistry correctly, CaCL2 is exothermic. So it would probably be best to mix it, let it cool, then use for an aquarium.

A quick search on Google for "CaCL2 exothermic" seems to substantiate my recollection here, but perhaps someone who is a chemist can chime in here?

 

[swylie]

It's the dissolution of CaCl2 that's exothermic, and yes, that's normal. The dissolution of anything in anything is exothermic, IIRC, it's just a question of how much so. If you add water to concentrated HCl the mixture can actually boil (and splash you and burn you.)

 

[rthomas]

Chemical grade

Thank you rusticitas and swylie.

BTW, is industrial grade chemicals safe enough for our tank. Or do we have to buy the more expensive lab grade chemicals?

 

[VaughnH]

We are just fertilizing, so either industrial or agricultural grade chemicals are fine. If we were doing analytical chemistry it would be a different story.

 

[rthomas]

Thank you for the clarification.