98 MARINE PRODUCTS OF COMMERCE 



cipitated the alginic acid from the solution in light gray albuminous flocks. It was 

 next filtered in a filter press and washed, forming a compact cake resembling new 

 cheese. It was either sold in this condition or dissolved in a sodium carbonate 

 solution. The solution was then partially neutralized with hydrochloric acid and 

 dried on trays in a well-ventilated room. The sodium alginate was thus obtained 

 in thin, almost colorless sheets, resembling gelatin but very flexible. The filtrate 

 from the alginic acid was evaporated and carbonized and iodine and potassium 

 salts recovered from the char. 



The substance which failed to dissolve when the fresh seaweed was treated 

 with the sodium carbonate was left as a residue after the first filtration. Stanford 

 named it algulose or algic cellulose. Although it contained no fiber, it consisted of 

 fine cellular tissue which, according to Stanford, made a transparent and very 

 tough paper. Algulose, dried to a very hard, dense mass, may be used in the 

 manufacture of buttons and knobs, etc. 



The Kelco Process. Algin and alginates are manufactured on a large scale by 

 the Kelco Company at San Diego, California and by the Algin Corporation at 

 Rockland, Maine. 



Giant kelp (Macrocystis pyrifera) is used as raw material by the Kelco Com- 

 pany. This company uses a process, originally patented by Green in 1936, which 

 avoids heating the solutions. It may be briefly described as follows: Freshly har- 

 vested kelp is leached for several hours with a weak hydrochloric acid solution 

 to reduce the salt content. The acid liquor is drained and discarded and the kelp 

 chopped and shredded. The product is digested with about 40 to 50 pounds of 

 soda ash per ton to give a pH of about 10. While cold, the resulting gelatinous 

 mass is given a second digestion with soda ash. The product is then completely 

 disintegrated in a hammer mill. Six volumes of water are added and the pulpy 

 mass maintained at a pH of 10.6 to 11.0. This is pumped into a tank where 

 clarifying agents are added and allowed to settle. A diatomaceous earth filter aid 

 is mixed with the supernatant liquor, which is then filtered through a plate and 

 frame filter press. 



The filtrate which contains the sodium alginate in solution is then treated with 

 a 10 per cent calcium chloride solution to precipitate the alginic acid as calcium 

 salt. The insoluble calcium alginate rises to the top and the lower layers of the 

 solution containing soluble salts and soluble organic matter are drained and dis- 

 carded. The curdlike calcium alginate is washed with fresh water and bleached 

 with a dilute sodium hypochlorite solution. 



After draining, the calcium alginate is converted to alginic acid by treatment 

 with 5 per cent hydrochloric acid. The excess acid and the calcium chloride are 

 drained oflF through a screen. The precipitate is rewashed with acidulated water, 

 agitated, and again drained. This process is repeated until practically all of the 

 calcium has been eliminated. 



Alginic acid prepared in this way is somewhat unstable and so must be stored 

 under refrigeration. Consequently, it is usually converted to sodium alginate or 

 other alginate by treatment with the proper carbonate, oxide, or hydroxide so 

 that it can be dried for shipment. 



Algin Corporation Process, According to this process, which has been patented 

 by Le Gloahec and Herter (1938), either fresh or dried Laminaria are soaked in 

 3 volumes of a cold 1 per cent fresh- water solution of calcium chloride. The sea- 



