Alkali the oxide or carbonate of one of the metallic bases, having a strong caustic power; usually applied to soda, potash, and ammonia. Of these substances the Hebrew appear to have been acquainted with two forms (see Thomson's Land and Book, 2, 302) concerning which the following are the Biblical notices.
1. Mineral alkali seems to have been designated by the term neither (נֶתֶר, "nitre," Pr 25:20; Jer 2:22; νίτρον, Attic λίτρον). It was found at all times in large quantities in two lakes of the valley of the Nile west of the river (Strabo, 17:803; Pliny 31:46), and is still obtained there from the water under the name of natrum (Paulus, Samml. v. 182 sq.; Forskal, Flor. Eg. p. 45; Andreossy, in the Memoires sur l'Egypte, 2, 27 sq.; comp. Descript. de l'Egypte, 12, 1 sq,.; Hasselquist, Reisen, p. 548). The Egyptians used nitre for embalming dead bodies (Herodotus 2:87); it was also employed instead of soap for washing (Jer 2:22; comp. Jerome, ad Proverbs 25, 20), as still appears to be customary in Egypt (Hasselquist, ut sup.; Forskal, Flor. p. 46). The property of this mineral, when dissolved in vinegar, of effervescing and losing its cleansing power, is alluded to in Pr 25:20. (See generally Michaelis, Comment. in Soc. Gott. praelect. Brem. 177, p. 134 sq.; Beckmann, Gesch. d. Erfind. v. 517 sq.) SEE NITRE.
2. Vegetable alkali is denoted by the Hebrew term borith (בֹּרַית, "soap," Jer 2:22; Mal 3:2), and by the Greeks and Romans likewise nitre (comp. Pliny 31:46). It was obtained by water (lye) from the ashes of the soap-wash (Arabic kale), of which Forskal (Flor. p. 64 sq, 54 sq., 98) found various kinds in Egypt, e.g. the Salsola kali, or the Mesembryantheum nodiorum of Linnaeus (comp. Hasselquist, Reisen, p. 225; Raffenan Delile, Flora AEg. illustr. in the Descript. de l'Egypte, 19, 81; see Oken, Botan. 2, 1:584; 2:856; Schkuhr, Botan. Handb. 1, 174 sq.). The saline plants indigenous in Palestine from which borith was obtained were also, according to the Talmudists (see Celsii Hierobot. 1, 450) and Jerome (in loc. Jer.), called by the same name, and are the same as those called by the Arabs ashnan. Of these plants Rauwolf (Reisen, p. 37) found in Syria two species; one was a thick bushy shrub, with numerous slender branches, surmounted by thick tufts, and furnished with narrow pointed leaves; the other in stem and top resembles "sheep-dew," with thick ash- colored roots (see his figures of each under Nos. 37, 38). The distinction of the various kinds of Oriental saline plants requires a new botanical treatment (Kitto, Phys. Geogr. of Holy Land, p. 268; Pliny, 19:18, mentions among the plants growing in Syria one "which yields a juice useful for washing wool," under the name vadicula, Gr. στρούθιον,
comp. Dioscorides, 2:193; Beckmann, Gesch. d. Erfind. 4, 18 sq.; Sprengel, ad Dioscor. 2, 478, regards this as no other than the Saponaria officinalis). Formerly, as at the present day (Rauwolf, ut sup.; Arvieux, Reisen, 2, 163; Belon, in Paulus's Samml. 4, 151), the ashes of these plants formed an important article of commerce in Oriental markets (thus their name al-kali is Arabic); end it is not only employed (in the form of lye or soap) as a means of cleansing clothes and the skin (Jer 2:22; Mal 3:2; Job 9:30), but also in the reduction of metals, e.g. silver and lead (Isa 1:25), and in the manufacture of glass (comp. generally Celsius, 1, 449 sq.; Michaelis, Commentat. ut sup.). SEE SOAP.