Hard ' or ' soft ' water refers to the amount of dissolved solids. Hard water is high in Magnesium and Calcium salts usually because t originates in underground locations where these salts are present. Hard water leaves a ring around the bathtub because of precipitation with soap. Soft water, such as rainwater, has much lower dissolved solids and should not leave a residue with soap. Bottled water i s commercially available at different prices, and is usually made by 'deionizing', or removing dissolved solids from the water through reverse osmosis or ion exchange processes.
Some bottled water arises from natural sources such as springs, and is sold at premium prices.
290 Body water is contained in cells, exists in extracellular spaces, and fills the blood vessels. These three locations for water are in equilibrium in the body, and water molecules move back and forth from location to location. The movement is controlled in various ways, but chiefly through changing concentrations of salt. Ions or electrolytes - These particles are soluble because their electrical charge attracts the polar water molecules. The water molecules serve to enshroud the charged particle and incorporate it into the water's polymeric structure.