288 



THE MANUFACTURE OF KELP. 



grammes. They have favoured me with the following interesting table of 

 the products annually extracted from this source by the seven principal 

 factories in France :— 





lode et 



Brome et 











USINES. 



Iodure de 



Bromure 



Chlorure de 



Chlorure de 



Sulphate de 



Nitrate de 





Potassium 



de 

 Potassium 



Sodium. 



Potassium. 



Potasse. 



Potasse. 





Kilos. 



Kilos. 



Kilos. 



Kilos. 



Kilos. 



Kilos. 



Le Conqiiet . 



20,000 



1,500 



800,000 



500,000 



200,000 



200,000 



Granville 



20,000 



800 



800,000 







1,000,000 



Cherbourg . 



5,000 





200,000 



180.000 



80,000 





Montsarac . 



4,500 





180,000 



150,000 



75,000 





Pont-1' Abbe . 



4,000 



200 



150,000 



140,000 



70,000 





Portsall . . 



4,000 





150,000 



140,000 



65,000 





Quatrevents . 



2,500 





100,000 



90,000 



50,000 







60,000 



2,500 



2,380,000 



1,200,000 



540,000 



1,200,000 



The lixiviation of British kelp is almost confined to Glasgow ; a small 

 portion only is worked in Ireland and Guernsey. There are six principal 

 lixi viators — of these, Mr. W: Paterson is by far the largest ; he works from 

 7,500 to 8,000 tons per annum. His enormous factory is well worth a visit, 

 and I am glad of an opportunity of acknowledging his attention and 

 courtesy in showing me over it. The process usually followed is suffi- 

 ciently simple ; the kelp is lixiviated with water, and the solution evapo- 

 rated ; the sulphate of potash deposits first in small crystals, and then the 

 chloride of sodium ; these are separately collected, and the solution is then 

 run off into iron coolers, where a crop of crystals of chloride of potassium 

 is deposited in three or four days. This process is repeated with the 

 mother liquor, and after the second crop of chloride of potassium has 

 crystallised out, the mother liquor is very dark and contains sulphides ; 

 oil of vitriol is added to decompose these, and much srdphur is precipitated ; 

 this is one of the bye-products of the factory. The liquor, after the addition 

 of the oil of vitriol, is decanted from the deposited sulphur, and distilled 

 with binoxide of manganese in leaden retorts ; the iodine sublimes, and is 

 received in earthern vessels. 



This process is simple and effective, and I can suggest no improvement ; 

 but its success is entirely dependant on the preparation of the kelp em- 

 ployed, and it is in the primary treatment of the seaweeds that reform is 

 so much needed. As I shall have further to speak of the working up of 

 seaweeds containing little iodine, I may just indicate that probably the 

 best means of extracting it from the mother liquor of these, would be that 

 recently discovered by MM. Stephanelli and Doveri. In their process, the 

 liquor is evaporated to dryness, mixed with peroxide of manganese, and 

 the iodine distilled off from earthern retorts ; this saves the oil of vitriol, 

 which is always used in Glasgow. I propose first briefly to enumerate the 

 disadvantages of the present method of making kelp ; then to examine 

 some suggestions for its improvement already proposed by others ; and, 

 lastly, to publish my own researches on the subject, and their results. 



