96 



C. J. WHITE. 



and L. stenophylla, but the quantity compares well with 

 most of the other Laminarise and is considerably greater 

 than that found in the Fuci. 



The following table taken from Thorpe 1 will give an idea 

 of the average yield of iodine of the chief sea-weeds of 

 North-west Europe: — 



Dry Weeds. 



Laminaria diyitata (stem).. 

 (frond) 

 ,, stenophylla 



„ saccliarina 



Fucus serratns 

 ,, nodosus 

 ,, vesiculosus ... 



Halidrys siliquosa ... 



Edible Japanese Sea- weed.. 



HymaiUlialia lorea ... 



Rhodomenia palmata 



Chorda filwm 



Zostera marina 



D'Urvillea utilis 



Macrocystis pyrifera 



Percentage 



Pounds Iodine 



Iodine. 



per ton. 



•4535 



10158 



•2946 



6-599 



•4777 



10 702 



•2794 



6-258 



•0856 



1-807 



•0572 



1-281 



•0297 



•665 



•2131. 



4-773 



•3171 



7-102 



•0892 



1-998 



•0712 



1-594 



•1200 



2-688 



•0457 



1023 



•0075 



•179 



•0308 



690 



Air-dry weeds carefully burnt to a loose ash give about 20°/ a 

 ash, so that the theoretical yield of the above Laminarise 

 should be 30 - 50 lbs. per ton. On the manufacturing scale 

 Thorpe estimates that 25 - 301bs.perton should be obtained. 

 As a matter of fact the average obtained by the kelpers 

 was less than 12 lbs. per ton, because in the early days the 

 weed was burnt solely for the sodium carbonate — for this 

 the kelpers had been taught to burn at a high temperature; 

 the quality of the sodium carbonate being thereby improved, 

 but much of the potash and most of the iodine was lost by 

 volatilization. When it no longer paid to prepare sodium 

 carbonate by this method (owing to the removal of the duty 

 from Barilla and the introduction of the Leblanc process) 



Dictionary of Applied Chemistry, Vol. n., p. 338. 



