Kelp

a general name for large seaweeds. The name is frequently restricted to a particular species whose long, slender fronds or floating blades not infrequently attain a length of 600 feet. Kelp thrown upon the beach by storms is dried in the sun and burned. A peculiar alkaline cinder or ash is obtained which is known commercially as kelp. Twenty or twenty-five tons of seaweed produce a ton of commercial kelp. A ton of kelp ash yields about eight pounds of iodine, several gallons of paraffin oil, and three or four gallons of naphtha, as well as other chemical products. It was at one time the principal source of soda, which is now obtained more cheaply from salt.