Model HA-71A - Hardness (Total) Test Kit, Drop Count Titration, Dual Range, 100 Tests
Hardness: Water hardness is caused almost entirely by calcium and magnesium ion. Other di- and trivalent metals have a similar effect, but usually are not present in high enough concentration in potable waters to cause problems. Hardness increases soap consumption in laundries and causes scale in boilers. Simply count the number of drops required to change the solution color to determine hardness concentration.