Barilla, or BARILHA, is properly, the Spanish name of a plant cultivated for its ashes, from which the purest mineral alkali is obtained; but likewise signifies that particular sort of vegetable alkali which is principally imported from Spain.

There are four plants cultivated by the Spaniards for this useful -purpose, namely, the Barilla, Ga-zul, Goza, and Salicor. But, as this account appears to be defective, we shall first present the reader with a list of those native vegetables from which good barilla has been extracted in Britain ; and next give a description of the most expeditious and profitable method of preparing this valuable material, for the various processes of washing, bleaching, etc.

Among the British plants, from which barilla or mineral alkali may be obtained, we shall at present enumerate the following, and then describe them in their alphabetical places:

1. Two species of the Salsola, Li or Salt-wort.

2. Two species of the Salicor-nia, L. or Glass-wort, and Sam-phire.

3. The Zoster a marina, L. or Glass-wreck.

4. Two species of the Triglochin, L. or Arrow-Grass.

5. The Chenopnd'mm album, and marttimum, L. or White and Sea Goose-Foot.

6 The Atriplex portulacoidc!, and littora/is, L. or Sea-Purslane and Grass-ORAch.

7. The P/antago maritima, L, or Sea Plantain.

8. The Tamarix gallica, L. or French Tamarisk.

p. The Erynghan maritiynum, L. or Sea Holly.

10. The Scdum Telcphium, h. or Orpine Stonecrop, or Livelong.

11. The Dipsacus fullonum, L. or Manured Teasel ; and

12. All the species of the Cynara and Carduus, L. or the Artichoke and Thistle, when cultivated either on the sea-shore, or in any soil irrigated with sea-water.

Barilla, as an article of trade, ought to possess the following properties : it should be firm, hard, and heavy, though porous; dry, and sounding on percussion ; of a blueish colour, and impart, on breaking it, a flavour slightly resembling that of the violet. By these criteria, it may be easily distinguished from pot-ash, though it would be difficult to procure a barilla consisting purely of mineral alkali;. as the very best sort of the former generally contains a small proportion of common salt. According to the experiments made by Mr. Kirwax, and published in the first volume of the Transactions of the Royal Irish Academy, in 1789, the barilla exported from Spain, contains carbonic acid, carbon, lime, clay, and silicious earth; but such as is very pure, also contains both common and Glauber's salt, and Mater. From the small quantity of carbonic acid discoverable in Spanish barilla, he concludes that its mineral alkali is for the most part combined with it in a pure or caustic state; and that its blueish colour must be ascribed to the matter of carbon : in a similar way, he attributes the green or blue colour of pot-ash to its combination with magnesia.

This important article of commerce is, in proportion to its degree of purity and strength, classed according to the following places, from Which it is imported: 1. The barilla made at Alexandria; 2. That from Alicant; 3. Carfhagena; and 4. Bourde, or Smyrna.

Various methods and schemes have, in this country, excited the, ingenuity of speculative men, in the production of this valuable sub-stance, for which large sums are annually paid at foreign mar". Those of our readers, who apply their attention to" experiments of this useful nature, will, perhaps, be gratified by the following specification of Mr. James Kings patent for his new-invented British barilla, granted in 178O. As his exclusive privilege is now expired, , we shall communicate the process nearly in the patentees own words. He first takes a quantity of ashes obtained from burning the loppings or branches of ash-wood, oak, beech, elm, alder, and any other kind of green wood and bramble, in the proportion of one-fourth: and a similar quantity of ashes obtained by burning the green vegetables, known by the name of fern, brecon, bean and pea-straw, and whin-ashes ; also common field and highway thistles; the stalks of rape and mustard seed; and the bent, or rushes, that grow by the seashore. One half of the ingredients being thus procured, they are then passed through a fine sieve, placed on a boarded floor, and carefully mixed with a similar quantity (making the other half) of soapboilers' waste ashes, which must be intimately blended together with. a shovel. Next, he adds one i dred weight of quick-lime to twelve times that quantity of the other materials, and likewise intermixes them thoroughly. After this preparation, the whole is put into large square iron pans, and a sufficient quantity of sea-water is poured on it to dissolve the lime, ashes, etc. while the mass is stirred with an iron rake, to effect, a more minute intermixture. A coal fire is now lighted under the pans, and kept briskly burning forty-eight hours, without intermission ; at the same time, the pans are continually supplied with sea-water, in order to impregnate these mate-rials with a greater degree of the saline quality, till they acquire a proper consistence for calcination in a melting furnace, known by the name of talcar. This apparatus is constructed in the usual manner, except that there is a wall above the grate-room, to separate the fire from the materials laid upon the bottom. An intense degree of heat is used in this cal-car, by means of which the saline mass boiled in the pan is completely dissolved, and afterwards kept in a state of fusion for one hour, during which time, the volatile part is expelled, and a fixed ali aline salt remains: this, being cooled in iron pans, produces our British barilla, resembling that imported from Spain. Mr. King also declares, in the pre amble to his patent, that this new chemical compound is calculated to serve as a substitute for manufacturing crown and broad window-glass, and also bottles, as well as for making soap and alum to much greater advantage, than any other material hitherto used in the production of those commodities.