海水中含碘量较少约为5×10~(-6)%而海藻等植物则含量较多,在风干的海带中有0.5%的碘,(但各地产品亦有不同,一般资料上记载为1吨海带或海菜可以制取碘10—12磅)。燃烧成灰后含有0.1—0.3%的碘,因为燃烧过程中挥发了部份的碘,所以最好应用回转炉,可以避免损失。称取1市斤海带烧灼后得100克黑色粒状物质,加水400毫升分两次浸取,煮沸2小时后过滤,在海带灰中除去碘化物外,尚有约30—70%可溶性物质及40—50%的不溶性物质,吸滤,除去不溶性残渣,在溶液中尚存在大部份的氯化物碘化物碳酸盐硫酸盐等硷金属及硷土金属的可溶性盐类,由于这些盐类的溶解度与碘化物有很大悬殊, Less iodine in seawater is about 5 × 10 -6%, while plants such as seaweed are more abundant, with 0.5% iodine in dried kelp, but there are also different products in different places. Take 10-12 pounds of iodine for 1 tonne of kelp or seaweed). Ash contains 0.1-0.3% after burning ash, because the combustion process of volatile iodine, it is best to use rotary kiln, to avoid losses. Weigh 1 kg catfish kelp after burning 100 g of black granular material, add water 400 ml twice leaching, boiling 2 hours after filtration, in the kelp ash to remove iodide, there are about 30-70% soluble material and 40 -50% of the insoluble material, suction filter to remove insoluble residue in the solution there are still most of the chloride iodide carbonate sulfate and other alkaline and alkaline earth metal soluble salts, due to the solubility of these salts There is a great disparity with iodide,