食盐因卤水来源、制作工艺的不同,分为海盐、池盐、湖盐和井盐四种。井盐的纯度高,内含钾、硼、碘等多种化学元素,是食盐中的“佳品”。海盐中含碘最丰富,常吃海盐可预防“大脖子”病,但海盐略带辣味,是食盐中的“中品”。池盐、湖盐味苦质劣,严重缺碘,为次品。我国对海盐的认识很早。相传在上古黄帝时代我们的祖先就知道从海中取盐。夏禹时出现了用海水熬盐,叫“煮海为盐”。《周礼·盐人》记载:“祭祀,共其苦盐,散盐。”(注疏:“散盐,煮水为之出 Salt due to brine source, the production process is different, divided into sea salt, pool salt, lake salt and salt four. Well salt, high purity, containing potassium, boron, iodine and other chemical elements, salt in the “good product.” Sea salt, the most abundant iodine, eat sea salt can prevent “big neck” disease, but the sea salt is slightly spicy, salt is the “goods.” Salt lake, lake salt taste poor quality, a serious lack of iodine, as defective. Our understanding of the sea salt very early. According to legend, in the ancient Yellow Emperor era our ancestors knew from the sea salt. Xia Yu appeared when boil salt with seawater, called “boiled sea salt.” “Zhou salt man” records: “sacrifice, a total of bitter salt, salt.” (Note Shu: "salt, boiled water out