盐是人类生活的必需品,也是化学工业的基本原料。海水中NaCl的含量为2.7%左右,是重要的制盐原料。利用海水制盐的方法共有三种,即太阳能蒸发法(亦称盐田法)、电渗析法和冷冻法。本期封面图案为利用太阳能蒸发法(亦称盐田法)制盐。中国是世界上盐田面积最大、海盐产量最多的国家。盐田面积达4 000 km~2,海盐年产量3 000多万吨,占全国原盐产量的70%,供应全国50%人口的 Salt is a necessity for human life and a basic raw material for the chemical industry. The content of NaCl in seawater is about 2.7%, which is an important salt raw material. There are three ways to make salt using seawater, namely solar evaporation method (also called salt field method), electrodialysis method and freezing method. The current cover pattern is the use of solar evaporation (also known as salt method) salt. China is the largest salt pan in the world and the country with the most salt production. Yantian area of ​​4 000 km ~ 2, annual output of 30 million tons of sea salt, accounting for 70% of the country’s salt production, supply 50% of the country’s population