Grains. Carbonic acid and sulphurctted hydrogen,.5 Sulphur,.1 . .
. . .
. .
Sulphuric acid, .. 2.04 . . . .
Muriatic acid,. . . 19.1 . . Insoluble matte, ..5 . . . . .
These were in combination with as much of the alkaline bases as was sufficient for their saturation. Experiments were made, to slim in what state of combination they exist ed, by observing what salts make their appearance in eva poration ; but these are now superseded by the subsequent ingenious researches of Dr. Murray, on the analysis of mineral waters and the waters or the sea, (see the Transac tions of the Royal 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 con sequently, that all the knowledge that is within our reach is obtained, when the proportions of different acids and bases contained 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 ascertaining the quantity of alkali contained in different specimens of kelp. Mr. Kirwan had employed a solution of common alum, and judged of the quantity of al kali 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 shewcd in a paper, contained in the Irish Transactions, that Cunnamara kelp contained of soda3 437 per cent. And when deprived of sulphur by the 4 457 action of carbonic acid, .
Strangford kelp,. . .
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 neu tralization of an acid of given strength. In his experi ments, lbs. oz.
Norway kelp contained in 100 lbs. .2 11 Shetland do. of indifferent value,2 6 Lewis do. . 2 11 . .
. . .
Arran do. .31 . . . .
Good Isla do.. .
. 4 Do. ).lull do. .4 . .
Do. Morven do.. . . . 4
.
Do. Skye do.. . . .
Leith do.. . . . Dr. Fyfc very properly gives the preference to the me thod of Dr. Black, as simpler and more easily employed by all who have any interest in knowing the value of different cargoes ; and the strength of the acid must be in the first place perfectly known. This is conveniently .'one by using sulphuric acid, the strength 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, al lowed to remain in mixture several days, and frequently shaken. One half of the clear solution is poured off, and this is saturated with the acid, litmus paper being employ ed as the test of the point of saturation. Tile quantity of acid which it has required is ascertained by using a small measure divided into grains, in adding the acid in succes sive 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 the kelp, even at the same place, varies considerably, depending, no doubt, on the circumstances which occur during the manufacture. This last circumstance renders it of importance, that the purchaser should always be able to judge of its value. It is shown in the same paper, that for want of some method for this purpose, high prices are sometimes given for very indifferent articles. L. 13. per ton was given for kelp con taining 42 per cent. while L. 11. 11 s. was given for an arti cle containing less than one per cent. It is on this ingre dient that the value of kelp to the soap-maker depends.
The following statement is given, of the composition of the insoluble part of kelp, as ascertained by experi ment.
The quantity of uncombined alkali in barilla was found to be more uniform than in kelp, and the average about 11 per cent. The whole soluble matter amounted to from one-half to two-thirds. In all respects, the number and kind of ingredients in kelp and barilla are the same, with the exception of iodine, which is contained in kelp, but not in barilla.