Barilla (Span, barrilla), or Soda Ash, a crude carbonate of soda, procured by the incineration of the salsola soda, salicornia, and other plants which are cultivated for this purpose in Spain, Sicily, Sardinia, and the Canary Islands. In Alicante the plants are raised from seed, which is sown at the close of the year in salt marshes near the coast, and they are usually fit to be gathered in September following. In October the plants are dried like hay, and then burned in holes in the ground capable of containing a ton or a ton and a half of soda. Iron bars are laid across these cavities, and the dried plants, stratified with dry seeds, are placed upon them. The whole is set on fire, and the crude soda runs out in a red-hot fluid state and collects in the bottom of the pit. As fast as one portion is consumed fresh material is added, until the cavity is filled with the alkali. The holes are then covered with earth, and the soda is allowed to cool gradually. The spongy mass, when sufficiently cold, is broken up and packed for shipment without further preparation. It rarely contains more than 20 per cent, of carbonate of soda; the impurities are chiefly common salt and sulphates of soda, lime, and alumina, with some free sulphur.
Soda ash is now manufactured artificially from common salt according to the method of Le Blanc. Kelp, made from the drift sea plants of the north of Scotland and Ireland, and varec on the northern coast of France, of similar origin, are still more impure than barilla. The principal uses of barilla are to furnish the alkali required in the manufacture of glass and soap.