October i, 1884.] 



THT. TROPICAL AGRICULTURIST, 



3'7 



approach the composition of that from wood : 



Seaweed. 



*Carbon ... 



Phosphates 



Calcium carbouate ... 



Calcium sulphate 



Magnesium carbonate 



Alkaline salt 



Silica, &c 



5254 

 1092 



15-56 



1134 

 5-70 

 3-94 



Hone. 



11-77 



77-70 



8-43 



•35 



109 

 •86 



♦Containing nitrogen ... 10000 ... 100-00 



Containing ammonia ... 1'75 ... 1"S 



My experience in the use of peat may be worth re- 

 cording I found it give a very fair red heat; we cut 

 and stacked about 600 tons a year of good quality in 

 North Cist, it cost 2s. 6d. per ton, anil I do not think 

 it can be obtained for less. There was no royalty or 

 rent, and the bog was close to the works. It required 

 three times the quantity compared with coal, which greatly 

 increases cost of firing. There is this peculiarity about 

 peat that, where a large supply is required, its cost in- 

 creases with the quantity collected, because a larger area 

 must be worked. 



The winter tangle forms hut a small part of the sea- 

 weed used for kelp. In the spring and autumn large 

 quantities of Bardarrig or tangle top come ashore, and 

 this is the substance most difficult to deal with. It is 

 ruined for kelp-making by rain, and it will not repay 

 cartage to a long distance. Even washing about in the 

 sea spoils it. To work it by my process would require 

 a large number of small works, which it out of the question, 

 so that it is still mostly made into kelp in the old way, 

 with all its attendant evils. It is this substance which 

 I propose now mainly to deal with. I am convinced that 

 no process will deal effectually with it unless it will 

 afford the means of removing it to central works, say at 

 (ilasgow, involving a cost for carriage equal probably to 

 the cost of the weed, doubling in fact its first cost. There 

 are two ways of removing it, either wet or air dry. I 

 prefer the latter, although I have proved that it can be 

 perfectly weli kept in a silo, a specimen so kept for several 

 months having reached me perfectly goo,], and still con- 

 taining 83'8 per cent moisture ; and it has been also proved 

 that such a covering of earth as that used foi potatoes is 

 an available silo. Most of this material can, however, he 

 got air dry. if. as soon as obtained, it is put in a rick 

 and thatched over, a good deal of it being lost at present 

 while they are waiting for enough to burn into kelp, which 

 cannot be' made in a small quantity, and for a way they 

 have of putting it in small stacks to get damp again, 

 because thev object to burning it too dry. Twenty thou- 

 sand tons of this dry material could easily begot in Ireland 

 alone. Four hundred thousand tons of the black wrack 

 was the usual annual collection in the Hebrides in former 

 years, now all unutilised, so that there is ample mat, rial 

 if use can be found for it. It is a well-known fact that 

 the Feci grow better when regularly cut. 



We are "not, of course, limited to Ireland and the High- 

 lands, as any demand for the raw material would offer 

 up new and very extensive sources of supply. 



The differenci between kelp-making and distillation in 

 retorts is shown by the following actual experiment on 

 eight tons of tangle. Four tons were burnt with great 

 care into kelp, and four tons were carbonised in a retort 

 with the following results:— 



Cwt. Per cent. 



Kelp produced 15 ... IS 7 



Char „ 30 ... 37'5 



Salts. Iodine, 



cwt. lb. 



Produce of char ... 877 ... 20 25 

 kelp 657 ... 13-27 





Loss in kelp 220 1598 



„ per ton of tangle ... 053 400 



As a rule the kelp does not contain anything like this. 

 The presence of sand particularly adds much to the 

 volatility of the iodine. 



A rich sample of seaweed ash, exposed in a platinum 

 capsule over an ordinary Bunsen burner for twenty-four 

 bonis, will not retain a trace of iodine. 



The sand in kelp is either shell sand, which is mostly 

 carbonate of lime, or flint sand, which is silica ; both are 

 highly prejudicial, as the following experiment shows — 

 100 grains of a rich seaweed ash was in each case heated 

 for ten hours over an ordinary Bunsen burner. 



Per lb. 



cent. y ton. 

 The ash contained of iodine ... -S930 ... 20 



The ash after heating ten hours ... 4911 ... 11 

 The ash with 50 per cent limestone -3572 ... 8 

 The ash with 50 per cent sand ... -2235 ... 5 



MEW PROCESS. 



The salts made from kelp at present are as follows 

 taking an average on 20,000 tons: — 



Per ton. 



Muriate (95 per cent potassium chloride) ... 5 cwt. 



Sulphate (75 „ potassium sulphate) ... 18 



Kelp salt (sodium chloride, containing car- I 



bonate = 8 per cent alkali J * •• 



10-6 

 Iodine, 12^ lb. per ton. 



I found, in the first instance, that these salts could be 

 easily extracted from the seaweed, by simple maceration 

 in cold water ; the amouut so removed from air dry 

 laminaria is pretty regularly about one-third of the weight, 

 or 33 per cent, of which 20 to 22 per cent are mineral 

 salts, and the balance consists of dextrine, mannite, and 

 extractive matter ; leaving two-thirds of the plant, or 66 

 per cent, for further treatment, apparently unaltered. 



This residue contains a peculiar new substance, to which 

 I have given the name, of Algin ; and the cellulose; the 

 whole plant being thus utilised. 



The comparison between the three processes will, there- 

 fore, be as follows, on 100 tons of air dry Laminaria : — 



KELP PROCESS. 



Per cent utilised, IS. 



Keln IS tons I Salts, 9 tons. ) Residuals— Kelp waste, 



'• l8tons - J Iodine, 270 lb. ( 18 tons, valueless. 



CHAR PROCESS. 



Per cent utilised, 36. 



Char. 36 tons. 



} Salts, 15 tons. {Residuals-Charcoal, 36 



i Iodine, 600 lb. I tons '. tar " a -"> a, »- 

 I J monia. 



WET PROCKSs 



Ter cent utilised. 70. 

 AVater extract, f Salts, 20 tons. { Residuals-Algin 20tons, 



33 tons. I Iodine, 6001b. ' °<AWoBe 15 tons, dex- 



(. ) trine, &c. 



Showing that the last process has the first advantage of 

 taking out more salts and iodine from the weed than any 

 other; and these, even at present prices, are sufficient to 

 recoup all the expense of carriage and working. More- 

 over, in the two prior processes, the residuals are those 

 of the first product, in the last these are from the weed 

 itself. 



The water extract is carbonised, and the salts extracted. 

 1 append analyses of these; they differ from the kelp in 

 containing no sulphides, and in containing calcium and 

 magnesium salts. 



AIR DRY (l.AMlNARIA STEXOPHYLLA). 



21 pel- cent salts. 



Per cent. 



Calcium sulphate ... ... 1-93 



Potassium sulphate ... ... 9-72 



Potassium chloride . . ... 31'97 



Sodium chloride ... ... 4S'67 



Sodium iodide ... ' ... ... 1-79 



Sodium hydrate ... ... ... 0'13 



Magnesium chloride ... ... 5'74 



99-95 



RESIDUAL WEED (LAMINARIA STENOPHYLLYA). 



2-32 per cent salts. 



Per cent. 



Potassium sulphate ... ... 35*27 



Potassium chloride ... ... 6'72 



Potassium carbouate ... ... 5-00 



Sodium carbonate ... ... 4997 



Sodium iodide ... ... ... 263 



9959 



