I have calcium chloride in the form of small (1-2 mm) round white pellets, originally bought at a home-brew shop. The packaging gives no indication what hydrate it is. Since each water molecule adds ~16% of the weight of anhydrous CaCl2 this introduces a big error when using it to treat water to a specified amount (in ppm).
Naturally I figured I could throw it in the toaster-oven for a while at 350°F and weigh it every 15 minutes, to figure out how much water was driven off. Results:
0 min. - 1.15 g. 15 min. - 0.92 g. 30 min. - 0.90 g. 45 min. - 0.90 g.
I originally assumed this would be anhydrous, but after reading that calcium chloride dihydrate decomposes at 347°F, and calcium chloride monohydrate decomposes at 500°F, I'm not so sure.
I couldn't find any other information on figuring out the hydrate online or indicating what state calcium chloride is typically in (at least that I could understand). Am I correct in thinking I'm left with the monohydrate? Or is it actually anhydrous?