After the water boils, a portion of the water evaporates and the insoluble calcium sulfate (CaSo4, gypsum is calcium sulfate containing crystalline water) precipitates. The previously dissolved calcium bicarbonate (Ca (HCo3) 2) and magnesium bicarbonate (Mg (HCo3) 2) decompose in boiling water, releasing carbon dioxide (Co2) and becoming insoluble calcium carbonate (CaCo3) and magnesium hydroxide (Mg (OH) 2), which are also precipitated. This is the origin of scale.

For ordinary families, the impact of scale may not be significant. But for factories, the problem is big. Some large boilers used for heating and steam supply in factories send out several tons of steam per hour, which is equivalent to burning several tons of water dry. According to experiments, there are approximately 1.6 kilograms of minerals in one ton of river water; The mineral content in a ton of well water can reach around 30 kilograms. How astonishing the amount of scale that hard water deposits on the inner wall of the boiler when transporting dozens of tons of steam in a day! The large boiler is encrusted with scale, like building an insulated stone wall between the steel plates on the boiler wall and the water. The boiler steel plate cannot touch the water, and the furnace fire keeps burning the steel plate until it turns red. At this point, if cracks appear in the scale, the water immediately leaks onto the high-temperature steel plate, rapidly evaporating, causing a sudden increase in pressure inside the boiler, and an explosion is about to occur. The power of a boiler explosion is no less than that of a heavy bomb! The harm of visible scale cannot be ignored! Therefore, in factories, an appropriate amount of sodium carbonate (commonly known as soda) is often added to the water, causing the calcium and magnesium salts in the water to precipitate and remove, resulting in the water becoming soft water.