THE MANUFACTURE OP KELP. 301 



This is best distilled by the agency of steam. The first portion which 

 comes over is the naphtha ; this is collected separately, the weaker liqnor 

 subsequently distilled being returned to the still with the next charge. 

 Eedistillation over quick lime yields it in a state of purity. The solution 

 of chloride of ammonium remaining in the still is run out, evaporated* 

 crystallised, and the crystals sublimed according to the ordinary method 

 of making sal amm oniac of co mm erce. 



This, then, is the process, and it offers the following advantages : — 



1. Retention of the whole of the iodine. 



2. Easy and rapid lixiviation, colourless solutions and pure salts. 



3. Absence of sulphur compounds in the mother liquor, great saving 

 of oil of vitriol, and no evolution of poisonous gases. 



4. Factory to a great extent self-supporting, having its own means of 

 heat and light, the fuel being extracted from the weed itself. 



5. Manufacture continuous, affording employment to the kelpers all the 

 year round, and at a higher rate of remuneration. 



6. Extension of the manufacture, as this process allows a much larger 

 margin for profit, and admits of the lucrative working of the commonest 

 weeds, which will not, I anticipate, be allowed to rot on the shores of Great 

 Britain when their commercial value becomes known. 



These, then, are the principal features and advantages of this process ; 

 no doubt improvements may be developed in its minor details when it is 

 worked on a large scale, but its general plan I believe to be the desideratum. 

 If it be advisable that the ash should be sold for lixivation to replace the 

 kelp of commerce, it may be made more portable by raking the charcoal 

 out into the air, when it gently consumes at a low temperature, and forms 

 a loose ash containing very little carbon ; the charcoal would thus be sacri- 

 ficed, though an arrangement could easily be made by which it might be 

 allowed to fall into an open chamber under the drying shed, and its heat 

 of combustion thus made available. This might be adopted with poor 

 weeds, such as the grass wrack, which are largely mixed with sand ; but 

 all those employed in the present manufacture of kelp shordd, I think, be 

 treated as I have recommended. I have also tried distillation in a blast of 

 air, but although the products obtained are nearly the same, the tempe- 

 rature is so liable to rise with the attendant evils alluded to, that I prefer 

 the method I have indicated. Theories have been circulated amongst 

 scientific men to show that the weeds on the Irish and Scotch western 

 coasts only contain iodine in quantity, because they are nourished by the 

 Gulf Stream, which impinges on these coasts, and is considered to be the 

 carrier of iodine from the Gulf of Mexico. My experiments have led me 

 to the conviction that iodine is pretty universally distributed in sea-water ; 

 that a large proportion of iodine is confined to a very few species of algge, 

 though nearly all contain traces ; and that those species contain the same 

 proportion wherever they may be found, but differing for each species and 

 the way in which they are burnt. Thus, the weeds on which my experi- 

 ments were conducted, were all collected on the south coast of England 

 where they have been supposed to contain no iodine. Reference to my 



