1869.] a?id their Uses. 335 



manure is to allow it to ferment above high-water mark in alternate 

 layers with either turf-mould or clay, and that the native ]Aan is 

 very wasteful in every respect." 



If the sea-weed is to be used for kelp burning, a gravelly beach 

 (if there be no fine sand) is considered a good place on which to have 

 it driven ; but if there is sand the latter will adhere to the weed and 

 cannot be got off even when it is dried, therefore both must be 

 burned together. This deteriorates the kelp, as it adds consi- 

 derably to its weight, and also decomposes the iodine compounds, 

 which causes some of that metalloid to be volatilized — the former 

 being a loss to the buyer and the latter to the seller.* 



The weed having been fully dried, is stacked in heaps until a 

 sufficient quantity is collected, when the fires are lighted. The 

 burning is effected in rude kilns built of loose stones, of which 

 the dimensions are about eight feet long, three wide, and eighteen 

 inches high, the "eye of the kiln" being placed opposite to the 

 wind to catch the draft. This is the plan usually adopted, but in 

 some localities they are made longer and narrower. The best kelp 

 ought of course to be made entirely from red weed ; however the 

 operators often mix with it any black weed or reeshagh at hand, 

 more especially "Chorda filum" and "Himanthalia lorea." The 

 price of red weed kelp ranges from 3?. to 5/. a-ton, according to the 

 quantity of iodine it contains, as all lots are examined previous to 

 purchase by the sulphmic acid test. 



AVhen writing of iodine, Apjohn says, in reference to its 

 manufacture,! " The burning of the fuci must not be effected at 

 too high a temperature ; for if so, much of the iodides will be 

 volatilized, or decomposed by the silex present m the ash. The kelp, 

 broken into small fragments, is digested with boihng water, which 

 dissolves out the soluble salts, amounting on an average to about 

 haK its weight. This solution is then boiled down, imtil a film 

 forms on its surface, and set to crystallize, when sulphate of soda, 

 carbonate of soda, and a good deal of chloride of potassium, are 

 separated. The mother liquor, which still includes the iodides, 

 mixed with chlorides, sulphides, carbonates, sulphites, and hypo- 

 sulphites, is heated with one-eighth its bulk of oil of vitriol, when 

 carbonic acid, sulphurous acid, and sulphide of hydrogen are dis- 

 engaged in the gaseous form, and sulphur is set free. Upon 

 standing, the sulphur subsides, and along with it additional crystals 

 of sulphate of soda. The liquid which remains, and in which the 



* A -wilful fraud committed by the burners on the buyers is the tlirowing into 

 the mass of kelp, when fluid, lumps of slag procured at the different forges 

 throughout the country ; also pounded granite, gravel, &c., all of which add con- 

 siderably to its weight. 



t ' Manual of the Metalloids,' by James Apjohn, M.D., F.E.S., M.E.I. A., &c., &c. 



