96 MARINE PRODUCTS OF COMMERCE 



Table 22. Algin Content of Various Algae. * 

 (Water-free basis) 



Alga Algin 



Per Cent 



Macrocystis pyrifera, leaves Average, 20 samples 16.2 



Macrocystis pyrifera, stems Average, 20 samples 18.2 



Nereocystis leutkeana, leaves Average, 4 samples 14.4 



Nereocystis leutkeana, stems Average, 4 samples 13.6 



Pelagophycus porra, leaves Average, 2 samples 16.1 



Pehgophyctts porra, stems Average, 2 samples 15.9 



Egregia laevigata, entire plant Average, 2 samples 18.7 



Egregia menziezii, entire plant Average, 3 samples 19.1 



Laminaria andersonii, entire plant 22.8 



Iridoea sp., entire plant 1.0 



Laminaria digitata, stem 33.3 



Laminaria digitata, leaves 31.9 



Laminaria stenophylla, stem 39.2 



Laminaria stenophijlla, leaves 40.1 



According to chemists who have studied its structure, alginic acid is a hydro- 

 philic colloidal polymer of anhydro -yS-<i-maiinuronic acid (Schoeffel and Link 

 1933; Niemann and Link 1933; Nelson and Cretcher 1929) with the empirical 

 formula (CoHgOs),.. Alginic acid reacts with carbonates to produce carbon dioxide 

 and may be titrated with an alkali to an end point by using a phenolphthalein 

 indicator. It does not give the reducing sugar reaction with Fehling's solution, but, 

 if dried at 212° F (100° C) or boiled with water or dilute acid, it may be con- 

 verted into reducing substances. It has an optical rotation of approximately 



NS=- 



133°. 



Harvesting of Seaweed for Algin Manufacture 



On the European and American coasts of the North Atlantic the "horsetail 

 kelp", Laminaria digitata, and the broadleaf or sugar kelp, Laminaria saccharina, 

 are harvested for use in making algin. The kelp is usually gathered in motorboats 

 equipped with grappling hooks operating at depths of 10 to 20 feet. Some is also 

 collected in dories by fishermen who rake it from the bottom in shallow water, 

 or gather it as driftweed along the shore after storms. 



Along the coast of California and Lower California there are many enormous 

 beds of the giant kelp, Macrocystis pyrifera, which are often several square miles 

 in area. Thousands of tons are collected each year south of Point Conception, 

 California. The kelp is harvested by means of an underwater mowing machine 

 carried by a motor-driven barge. A horizontal cutter bar 10 feet or more in 

 length is operated at the bow of the boat about 3 feet below the surface. After 

 the kelp is cut, it is automatically hoisted aboard the barge by an inclined chain 

 conveyor. The edges of the elevator are fitted with knives to prevent it from be- 

 coming clogged. Some of the barges hold as much as 300 tons of kelp. 



" Hoagland, D. R., "Organic Constituents of Pacific Coast Kelps," /. Agr. Res., 4, 

 39-58 (1915). 



