430 



KELP. 



Kflp. 



Chemical 

 analysis of 

 kelp. 



burning of the fuci, in the treatment of the a&hes, in 

 their fusion, nntl the degree of exposure to the air du- 

 ring these processes, as the alkali is apt to be dissipa- 

 te<C by neglect or excew, in a variety of particulars. A 

 knowledge of the most advantageous process in burn- 

 ing is still a desideratum ; and, at the present moment, 

 ( iTslS,) the Highland Society holds out the promise of 

 nil honourable testimony of its approbation, to the au- 

 thor of the best satisfactory experimental account of 

 that subject. 



Till very lately, it seemed a matter of difficulty among 

 manufacturers who purchase kelp, to assure themselves 

 of the comparative value of different cargoes. The pro- 

 cesses of chemists for estimating the amount of alkali 

 contained in it had been various, and some of them ap- 

 peared to imply a degree of trouble in the manipula- 

 tion, which was too inconvenient, and perhaps too un- 

 certain, for habitual application to mercantile use. To 

 remove this disadvantage, was bne object with the 

 Highland Society, for which they offered two of their 

 prizes. In consequence of which, we have two judici- 

 ous essays on the subject, both deemed worthy of the 

 proffered mark of encouragement one by Dr. Fyfe, and 

 another by Mr. Parkes. The first of these is most ex- 

 tensive in its objects, and in a form best adapted to di- 

 rect application to practice. Meritorious new discover- 

 ies are sometimes inferior in utility, to the well execu- 

 ted task of rendering those available which are already 

 made, pointing out the most judicious choice among 

 many proposed expedients, and removing from the 

 minds of those concerned all discouraging impressions 

 of the difficulty of the subject. This essay has for one 

 chief object the comparison of kelp and barilla; an im- 

 portant problem, as leading us to discover how far the 

 domestic falls short of the foreign article, and what hope 

 may be encouraged of rivalling the latter in the mar- 

 ket, without the aid of the questionable policy of a 

 heavy duty, tending to exclude from our manufactures 

 the employment of the cheapest article. We shall fol- 

 low the order in -which the subject is treated in the es- 

 say now mentioned. 



The soluble part of any fair sample of kelp, is sepa- 

 rated by boiling it in water, after it has been duly com- 

 minuted. The proportion of it that was found in the 

 experiments of Dr. Fyfe, varied from about one-third to 

 two-thirds of the whole. The constituent parts of it are 

 ascertained by two different processes ; the one consists 

 in the application of the different chemical tests to the 

 whole in a state of solution, the other in making it 

 yield its saline ingredients in a crystallized form, by 

 the process of evaporation. The effects produced on 

 the vegetable colours show the presence of an alkali, 

 either uncombined, or in union only with the carbonic 

 acid. This is well known to be soda. A quantity of 

 potassa likewise exists in it, and shews itself, by giving 

 with tartaric acid a precipitate, which is soluble in the 

 muriatic acid. There is no neutral salt with an earthy 

 or metallic base. The existence of such a compound is 

 excluded by the superabundance of free alkali, and this 

 absence is confirmed by the employment of the tests, 

 by which such base would be detected. The presence 

 of sulphuric acid is shown, by a precipitate formed 

 with the muriate of baryta, and which is not soluble in 

 muriatic acid. The presence of muriatic acid is shown, 

 by the insoluble precipitate the muriate of silver form- 

 ed when it is treated with nitrate of silver. Other ex- 

 periments were made, by which the following ingre- 

 dients, besides the alkali, were found to be contained 

 in 100 grains of the saline matter. 



Carbonic acid and sulphuretted hydrogen, 



Sulphur, 



Sulphuric acid, .... 



Muriatic acid, . * 



Insoluble matter, .... 



Grains. 



.5 



.1 



8.04 

 19.1 



.5 



Kelp. 





These were in combination with as much of the al- 

 kaline bases as was sufficient for their saturation. Ex- 

 periments were made, to shew in what state of combi- 

 nation they existed, by observing what salts make their 

 appearance in evaporation ; but these are now super- 

 seded by the subsequent ingenious researches ofDr. Mur- 

 ray, on the analysis of mineral waters and the waters of 

 the sea, (see the Transactions of the Koydl Society of 

 Edinburgh, vols. vii. and viii. ) : 'from which it appears, 

 that the same solutions afford neutral salts differing in 

 chemical constitution according to the process by which 

 these formations are separated ; and consequently, that 

 all the knowledge that is within our reach is obtained, 

 when the proportions of different acids and bases con- 

 tained in any mixed solution are determined; These 

 ingredients were the same in the saline matter procured 

 from different specimens of kelp, though in various pro. 

 portions. 



The principal object -which was wanted, was an easy Method of 

 method of ascertaining the quantity of alkali contained ascertaining 

 in different specimens of kelp. Mr. Kirwan had em- the P r P^ r - 

 ployed a solution of common alum, and judged of the j" 

 quantity of alkali by the quantity of aluminous earth 

 which the solution was found capable of precipitating 

 from the sulphuric acid, to which in that substance it 

 is united. By this method, he shewed in a paper, con- 

 tained in the Irish Transactions, that Cunnamara kelp 

 contained of soda . . . 3.437 per cent. 



And when deprived of sulphur by 1 . .^_ 



the action of carbonic acid, 

 Strangford kelp, . . 1.25 



Professor Jameson made experiments on different 

 kinds of kelp by the application of this test, and also 

 by that which was first recommended by Dr. Black, viz. 

 the neutralization of an acid of given strength. In his 

 experiments, 



Ibs. nz, 



Norway kelp contained in 100 Ibs. . . . 2 11 



Shetland do. of indifferent value, . . . 2 6 



Lewis do. . 211 



Arran do. 3t 



Good Isla do. ....... 4- 



Do. Mull do. 4 



Do. Morvcn do. I' 



Da. Skye do . 6" 



Ijeitli do. 4 



Dr. Fyfe very properly gives the preference to the 

 method of Dr. Black, as simpler and more easily em- 

 ployed by all who have any interest in knowing the va- 

 lue of different cargoes ; and the strength of the a.cid 

 must be in the first place perfectly known. This is 

 conveniently done by using sulphuric acid, the stre. gth 

 of which is readily ascertained by its specific gravity. 

 A given weight of kelp reduced to powder, is mixed 

 with a given weight of boiling water, allowed to remain 

 in mixture several days, and frequently shaken. One 

 half of the clear solution is poured off, and this is satu- 

 rated with the acid, litmus paper being employed as 

 the test of the point of saturation. The quantity of 

 acid which it has required is ascertained by using a 

 small measure divided into grains, in adding the acid 

 in successive portions. The results of this test on 35 

 specimens are given, from which it appears that the 

 proportion of alkali varies from 1 to 6 per cent, and that 



