KELP (in M.E. culp or culpe, of unknown origin; the Fr.

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• EQUIVALENT

equivalent is varech)  , the ash produced by the incineration of various kinds of sea-weed (Algae) obtainable in great abundance on the west coasts of Ireland and Scotland, and the coast of Brittany . It is prepared from the deep-sea tangle (Laminaria digitata), sugar wrack (L. saccharina), knobbed wrack (Fucus nodosus), black wrack (F. serratus), and bladder wrack (F. vesiculosus) . -The Laminarias yield what is termed " drift-weed kelp," obtainable only when cast up on the coasts by storms or other causes . The species of Fucus growing within the tidal range are cut from the rocks at low water, and are therefore known as " cut-weeds." The weeds are first dried in the sun and are then collected into shallow pits and burned till they. form a fused mass, which while still hot is sprinkled with water to break it up into convenient pieces . A ton of kelp is obtained from 20 to 22 tons of wet sea-weed . The average composition may vary as follows: potassium sulphate, xo to 12%; potassium chloride, 20 to 25%; sodium carbonate, 5%; other sodium and magnesium salts, 15 to 20%; and insoluble ash from 40 to 50% . The relative richness in iodine of different samples varies largely, good drift kelp yielding as much as-xo to 15 lb per ton of 22i cwts., whilst cut-weed kelp will not give more than 3 to 4 lb . The use of kelp in soap and glass manufacture has been rendered obsolete by the modern process of obtaining carbonate of soda cheaply from common salt (see IODINE) .