Why all asbestos nets and were changed to clay nets in the ninth-grade chemistry textbook in the fall of 2022
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The new textbook of the People's Education Press in the fall of 2022 changed all asbestos nets to clay nets.
P94, asbestos net- clay net, modification notes
original
current
new textbook is marked in the 94 pages of notes. : It is recommended that this experiment be demonstrated by the teacher. The clay mesh used in the experiment is a substitute for asbestos mesh.
Asbestos mesh is a commonly used experimental instrument in chemical experiments. It is made of cotton cloth soaked in asbestos water sandwiched between two pieces of wire mesh. It is used to stand on a tripod or iron ring on an alcohol lamp when heating liquids. Its function is to disperse the heat of the flame to every corner of the container so that the is heated evenly to prevent the instrument from breaking due to uneven heating.
However, there are many small asbestos fibers on the asbestos net. If during use, under the action of external force or the heating temperature reaches 500℃, the asbestos fibers will float in the air. These tiny fibers, which are almost invisible to the naked eye, are absorbed by the human body. After inhalation, it will adhere to and deposit in the lungs, causing lung diseases and fibrosis of tissue in the lungs. Asbestos fibers accumulated in the body for a long time can also cause malignant mesothelioma, lung cancer, laryngeal cancer, ovarian tumors, etc. Serious illness. According to statistics, asbestos-related diseases cause more than 100,000 deaths every year.
Most of the chemistry laboratories in middle and high schools across the country use asbestos nets. The tiny asbestos fibers that escape from the asbestos net can easily float in the air and be inhaled by the human body, endangering the health of teachers and students.
More than 60 countries have banned the use of asbestos. In our country, some asbestos products have also been banned. The International Health Organization classifies asbestos as a Class I carcinogen.
Therefore, I think this may be the reason why the new ninth-grade chemistry textbook of the People's Education Press has changed all asbestos nets to clay nets.
Clay mesh is made of two pieces of wire mesh sandwiched between a piece of cotton cloth soaked in clay water and then dried. Its function is the same as that of asbestos mesh, but it is safer. Therefore, clay mesh can be used instead of asbestos mesh.
In addition, you should know that the instruments that need to be padded with clay nets when heating in the laboratory include: beakers, round-bottomed flasks , Erlenmeyer flasks .
Well, that’s it for today’s sharing. I hope it will be helpful to you.
