52 Journal of Agricultural Research voi. iv, no. i 



solutions, but no evidence of volatile sulphur could be obtained. Various 

 samples of kelp were also boiled with alkali, but no tests for lead- 

 blackening sulphur were apparent. The possible presence of volatile 

 sulphur lost on drying has not yet been verified. Further work is 

 planned to clear up these points. 



FORMS OF lODIN IN KELP 



Various researches have shown that many forms of marine life, such 

 as the coral and the sponge, contain large amounts of iodin in combina- 

 tion with proteins or amino acids (9, 17, 33). By analogy it might be 

 assumed that the o.i or 0.2 per cent of iodin present was also organi- 

 cally combined. Eschle (7) studied Fucus vesiculosus and Laminaria 

 digitata with this in mind. He found that he could only extract 10 per 

 cent of the iodin from the dried weed with boiling alcohol. From this 

 and other extraction experiments he concluded that most of the iodin 

 was organically combined. 



Extractions of dried samples of Pacific coast kelps made in this labora- 

 tory indicate that nearly all the iodin is extractable by cold water or 

 90 per cent alcohol. From the aqueous solutions iodin may be set free 

 by dilute potassium permanganate or potassium nitrite, which would 

 lead to the inference that the iodin is present in ionic form. To deter- 

 mine whether the iodin could be completely extracted by water, a sam- 

 ple of dried and ground kelp was repeatedly digested and washed with 

 warm water until the washings showed no further test for chlorin. The 

 residue was foimd to still contain 5 per cent of the total quantity of 

 iodin present. Another sample was treated in a similar manner, except 

 that a very dilute alkali was used first for extraction. In this case the 

 residue retained only a faint trace of iodin. It is possible that a small 

 percentage of iodin is always present in organic combination, soluble in 

 alkali, while a much larger amount exists as the iodid. Bromin is also 

 found in the kelp, but only in one-fifth to one-tenth the quantity of 

 iodin. The analysis of sea water shows a quite opposite condition, the 

 amount of bromin largely exceeding that of iodin. There is a marked 

 selective power in the kelp for iodin, although the exact function of this 

 element is not known. Certainly the quantities of iodin retained by 

 these plants are enormous as compared with the concentration in the 

 sea water which bathes them. The selective action for potash is of 

 course almost equally striking, but this difference is of interest; much 

 of the potassium chlorid effloresces out as the plant dries, while no iodin 

 is demonstrable in the effloresced salt. Many questions bearing on the 

 essential or nonessential character of the various chemical elements pres- 

 ent in kelp could be solved only by propagation in artificial!)' controlled 

 solutions. Such experiments would be of extreme interest, but would 

 be difficult or impossible of execution. 



