Water contains trace amounts of calcium and magnesium and their content is expressed as water hardness. Hardness refers to the amounts of calcium ions and magnesium ions in water converted to an equivalent amount of calcium carbonate (CaCO3), and is expressed in terms of milligrams per one liter of water. The total amount of both hardness types (calcium and magnesium) is referred to as total hardness. Generally, a total hardness of 100 mg/L or less is referred to as soft water and 100 mg/L or more is referred to as hard water. While most water in Japan is soft and well suited to tea and soup stock, hard water is suited to supplementing mineral intake. Presently, the daily use of supplements to make up for insufficient intake of nutrients etc., has become common place. In the food sector, a variety of products are being produced to enable intake of the required amounts of such nutrients. Using Kyoritsu Chemical-Check Lab., Corp.'s PACKTEST series kit with the water analysis program for the UV-1280 UV-VIS spectrometer allows measurement of 22 types and
39 items, including total hardness and iron/zinc content. This article investigates the total hardness of commercially-available mineral waters as well as the hardness of tap water using the water analysis program for the UV-1280. We also introduce the measurement
results of iron and zinc content in a number of supplements.