Calcium chloride is usually used in place of Gypsum when sulfates are not desired.
Calcium chloride is used to correct mineral deficiencies in water which is to be used for brewing. It is used in demineralized or soft to medium hard water to increase permanent hardness. Used as directed, Calcium Chloride is effective in eliminating the variations in composition often encountered in water from surface sources. It will help establish proper pH of the mash and the wort and provide sufficient calcium ions essential for enzyme function, kettle protein coagulation and yeast metabolism
1 gram in 1 gallon changes the salt levels by 72 ppm calcium, 127.5 ppm chloride and adds 180 ppm to the hardness.