When water boilers are used for long period of time, the solid substances left behind as scale are

When water boilers are used for a long period of time, the solid substances left behind as scale are mostly composed of magnesium trioxosilicate (IV) and calcium tetraoxosulphate (VI). These substances are formed as a result of the reaction between the dissolved calcium and magnesium ions in the hard water and the anions in the soap used for washing. When water is heated, these substances tend to precipitate out of the water and form a hard layer of scale on the inner surface of the boilers. This scale can reduce the efficiency of the boilers and increase energy consumption, which is why it is important to periodically descale the boilers to remove the buildup.