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covered over with fand. The falts containedin thefe lakes are muriat and carbonat of foda,and it is remarkable that the proportions of thefetwo not only vary in the different lakes but in-different parts of the fame lake, fo much fo thatthe cryftalline depofits at that extremity of theJake which is the lhalloweft, and in which rufhesgrow, are principally carbonat of foda, whilethofe formed at the oppoGte extremity are al-moft entirely common fait. The lakes are fur-rounded with a band, fome yards in breadth, offaline efflorefcences, but the principal accumu-lations of fait are in the water at a little diftancefrom the bank. The natron appears to -beformed by the flow mutual decompofition of theJime-ftone and common fait aflifted by therufhes, up the fides of which the natron riles bythe force of efflorefcence: when the rufhes thusincrufted are broken by the wind, the foda on•their furface affumes its proper quantity ofwater, and forms a confufedly cryftallized ftra-tum of the thicknefs of from one to twelve inches,according as the weather and other circumftan-ces are more or lefs favourable to its production.In moft of the lakes the depoGtion of natrontakes place only at certain periods, in the inter-vals of which cryftals of common fait are pro-duced fo that the faline maffes which are dugout, efpecially in thofe parts that have been longundifturbed, prefent alternate ftrata of muriatand carbonat of foda. The efflorefcences onthe lhore of the lakes, and the detached cryftalsThat form in abundance at the water’s edge aremixed with a much fmaller quantity of commonfait than the more compact maffes, thefe latterhowever being rather more convenient to carry,and being procured with leaft trouble are con-ftantly preferred, and as no fubfequent purifica-tion is had recourfe to, the natron of Egypt isby no means fo valuable as it might ealily bemade. It is chiefly exported to Greece andother parts of Turkey, to Venice, to France ,and Britain . 0
The natron lakes in Hungary , like moft ofthe natural advantages of that rich country, arein a ftate of exceffive neglect: the only ones' that are put to any ufe are'four that lie-betweenDobritzin and’ Grofwaradin. Thefe in • thewinter feafon, when full of water, are from oneto two miles in circumference, but by the mid-dle of April or the beginning of May they aregenerally dried up, except fome pits that havebeen funk by art below the general level. In-afew days after the water has difappeared, thewhole furface of the cavity becomes white with* Memoirs fur l’Egypte, ■ ■> Jour, des Min'
faline efflorefcences of natron mixed with a littlefulphat of foda: thefe being removed, a frelhinevuftation is formed in three or four days, andcontinues to be renewed with equal rapidityduring the whole dry feafon of the year. Avery heavy fhower is fuificient to fill the lakes,but in a day or two they are dry again, fo thatno confiderable interruption is experienced tillthe latter end of • October; by this time thewater in the pits is fully faturated with natron,a confiderable proportion of which cryftallizesduring the firft frofts of autumn, and thusfiniihes the harveft of the year, for after thisthe rains fet in, and the lakes continue full ofwater till the enfuing fpring. The foil is a ftiffblue clay covered by a white calcareous fand,and is probably impregnated with fait as the fal-fola and other fucculent faline vegetables flourifhhere in great abundance. 11 The Hungarian aswell as the Egyptian natron feems to be hroughtinto commerce without undergoing any prepa-ration, as it appears in pulverulent maffes of adirty grey colour. The Hungarian natron hasbeen analyfed by Lampadius, and the Egyptianby Klaproth , e with the following refults.
natron natron
22.6 —— 14.2 Carbonat of Soda
20.8 — 9.2 Sulphat of Soda
15. — 22.4 Muriat of Soda
31.6 — 45. Water
9.2 Earthy refiduc
100.0 * 100.0
By far the greater part however of the fodathat is employed is of vegetable origin, and likepotalh, is procured from the combuftion ofplants. While the vegetables that grow incommon foil yield potalh, thofe which flourifhin fait water,- or on the fea lhore, or whereverthe ground is ftrongly impregnated with faityield foda-. Of vegetable foda there are twovarieties, namely, barilla and kelp; the formerbeing made from the plants of the genera falfolafalicornia, &c. that grow on the fea lhore, the-latter being - the -produce of fuci and othermarine plants. -
The bell barilla is made from the falfola foda,which is an object of extenfive and fedulouscultivation to the Spaniards, on the lhore of the-Mediterranean, efpecially in the vicinity of Ali-cant. Tt is fown in light low foils that are em-banked on the fide next'the lea, and furnifliedwith flood-gates, by which the fait' water maybe let in occafionally. In autumn when tliejs,:Np. : a> pi'llf. * Analyt, Elf, ii. p, 6o,