1 ppm = 1 mg/L, so 100 ppm = 100 mg/L

how much to add depends on the type of salt you are adding. remember that when you call calcium in the form of CaCl2, you are adding chloride too.

If you want to add 100 ppm calcium to 10 gallons of water using calcium chloride (anhydrous, not dihydrate)....

molecular weight of anhydrous calcium chloride is 110.9

mw of Ca = 40

mw of Cl = 35.45

40 + 2(35.34) = 110.9

therefore, each gram of CaCl2 is: 36% calcium and 64% chloride

to add 100 ppm calcium, you'd have to add 277 mg calcium chloride for each liter

X(0.36)=100 mg, X = 277 mg

10 gallons water = 37.85 liters

277 X 37.85 = 10,484 mg = 10.484 grams calcium chloride for 10 gallons of water

(you will also be adding 177 ppm chloride)

*note* beersmith versions 1 and 2 are wrong by assuming CaCl and not CaCl**2**.