Apr. IS. 191S Organic Constituents of Kelps 47 



CARBOHYDRATES IN KELP 



Carbohydrates or analogous bodies make up the principal portion of 

 the organic matter. The carbohydrates of these algae are complex 

 colloidal substances which would ordinarily be classified among the 

 vegetable gums, or pectins. Very little information is obtainable for 

 these groups, and there are no satisfactory specialized chemical methods 

 available for their study. In general, complex mucilaginous polysac- 

 charids are characteristic of marine algae (8, T. i, p. 68), replacing the 

 starch, cellulose, and simple sugars of most land plants. Even where 

 starch and simple carbohydrates have been reported to be present in 

 algae, the amounts are relatively small. The physical properties form 

 the most important consideration in the utilization of the carbohydrates 

 of the algae. From some products valuable jellies may be prepared, for 

 example, agar-agar. The California kelps studied in this laboratory 

 do not have this property of jellification to any valuable degree. 



ALGIN 



The fraction to which the name "algin" has been given is quantita- 

 tively and in point of interest the most important of the carbohydrate 

 constituents of kelp. Briefly described, algin may be separated from 

 the seaweed in the following manner: The material is digested cold for 

 24 hours with a dilute solution of sodium carbonate or other alkali. A 

 very thick, sirupy mixture results, which is filtered with suction. The 

 filtrate is treated with a slight excess of sulphuric or hydrochloric acid. 

 Immediately a heavy yellow precipitate is formed and floats in the 

 watery liquid. In its water-holding power this body may well be 

 compared with a sponge. On exposure to the air the color of the moist 

 precipitate rapidly deepens to a dark brown, and on drying it shrinks to 

 a dark-colored hard substance. 



Stanford, in the investigations already mentioned (24-31) in this 



paper, concluded that algin prepared in this manner was a definite 



chemical body. He assumed that nitrogen was an essential constituent 



/NHj. 

 and even advanced a definite formula : C-gH^gOoov Such a formula 



is without justification, since the elementary analysis was made on a 

 highly contaminated sample. Stanford further described a series of 

 salts of alginic acid with the heavy metals, and these, as well as the original 

 algin, he believed to be of considerable commercial importance. Smith 

 (21), in summarizing this and other work, compares algin with cottage 

 cheese and quotes the following analysis made by Stanford: C, 44.39 

 per cent; H, 5.47 per cent; N, 3.77 per cent; O, 46.37 per cent. 



More recently Kylin (15) has described an algin which he prepared 

 from Laminaria digitata and from several related species. Many of the 



