The main components of chalk:
Ancient chalk was usually made of natural chalk, but now it has been replaced by other substances. The main component of chalk is calcium sulfate, which is a white precipitate, not easy to decompose, and its particles are larger than dust. There are two kinds of chalk used in China: ordinary chalk and dust-free chalk. Their main components are calcium carbonate (limestone) and calcium sulfate (gypsum), or contain a small amount of calcium oxide.
Effects of chalk on health;
Writing on the blackboard with chalk means coating gypsum powder on the blackboard. Its particles are larger, mostly above 100 micron, heavier, falling faster and floating in the air for a short time. Most of them will not be inhaled into the lower respiratory tract, and gypsum itself is non-toxic to human body. So far, there has been no report in the medical field about lung diseases caused by inhaling chalk dust.
Although chalk dust is harmless to human body, millions of teachers in China write on the blackboard with chalk every day, and live in chalk dust after cleaning the blackboard every day, which will still cause nose, throat and throat discomfort.
Classification of chalk:
1, dust-free chalk
Dust-free chalk is an improved product of ordinary chalk, aiming at eliminating chalk dust pollution in classrooms. It just adds grease or polyol as binder to ordinary chalk, and then adds fillers with higher specific gravity, such as clay, putty, cement and so on. It can increase the specific gravity and volume of chalk dust and make it difficult to fly away, but in practical application, its effect of reducing chalk dust pollution is not very obvious.
2, non-toxic chalk
Non-toxic chalk is the healthiest chalk. It is made of pure gypsum, solidified and dried with water, and made of edible gypsum. This kind of chalk has been used in most foreign teaching since primary school.
Non-toxic chalk belongs to high-grade chalk and is non-toxic in the dust pollution of classroom chalk. After the dust generated by it is inhaled into the human body, the human body can directly discharge it through excretion and will not remain in the body. Even the water in production has zero pollution to rivers.