Mag. Chloride, why does the tablet dissolve?

Hello! Simple, almost random question here- I bought magnesium chloride as tablets for supplementation 'bout two months ago, and when I put them in my pillbox, exposed to the air, they grow soft, get beadlets of liquid on them, and sometimes totally dissolve. At one point I let one of the tablets sit on a little plastic dish to see how it would behave- it did not dissolve, but left a beadlet of liquid next to it, and the 'filler' material (the binder the tablet was made of) went soft. Also, if the magnesium chloride tablet is in contact with a gel capsule, it seems to slightly melt the gel capsule.

So I'm wondering about magnesium chloride. Is the liquid beadlets (they look a lot like water) the magnesium chloride itself? Is it water from the air that has been combined with the mag. Chloride? Is it particularly difficult to work with the stuff, and I was wondering too- what's the average intestinal absorbtion of the stuff?

I've read that vitamin D3 ups the absorbtion of minerals in the intestine, to the tune of 3-4 times more calcium, and I suspect it is the same for magnesium. I read that magnesium citrate is the material with the least side-effects, but it's absorbed at only 5-7% of the entire tablet (and I have no idea if that was with proper vitD3 supplementation between 4,000-10,000 iu/day @~200kg body weight). Tweet