Bru'n Water presumes that Calcium Chloride is anhydrous (100% pure). Most others presume that it is in the dihydrate state (~75.5% pure). Neither is correct sans for occasional blind luck.
I've tested fresh bottles of it twice in my day, and when first cracked open it is about 94-96 percent pure. But it is forever assimilating water from the humidity in the air, and before long it can be factually well less than 75% pure. But until it eventually turns into a liquid goo, it always looks the same.
If you have access to a precision analytical balance, put some on the balance, then sit back and watch its weight go up.