Table Salt

TABLE SALT, sodium chloride (NaCl), represents a food and flavoring substance of primary importance; it is used as a seasoning for dishes and has wide application as a harmless preservative for many food products. T. s. is consumed in large quantities for various agricultural and technical needs; it is used in the production of soda, hydrochloric acid, caustic soda, etc., and finds application in textile, dyeing, paper and other industries. (For physiological and medicinal significance of T. s.-see Sodium, Mineral Metabolism, Ions.)

According to the method of extraction, the following¹ types of T. s. are distinguished: a) sea salt, b) lake self-settling and pond salt, c) rock salt, and d) boiled salt. Sea salt is obtained from seawater by evaporating it under the action of solar heat in specially constructed coastal basins. As the water evaporates, the T. s. contained in it gradually settles to the bottom of the basin, from where it is extracted. This method of extraction is used in the USSR, mainly in the coastal areas of the Sea of Azov and the Black Sea, in the regions of Yevpatoria, Henichesk, Odessa, and Kherson. The total amount of sea salt extracted in the USSR, according to Soyuzsol data (1931), constitutes about 8% of all T. s. extracted in the USSR. - Lake self-settling and pond salt is extracted from the bottom of salt lakes formed from seawater. Self-settling salt is that obtained from naturally formed salt lakes; pond salt is that obtained from artificial coastal lakes formed by separating part of the sea with artificial barriers. The main places for extracting lake salt in the USSR are Lake Baskunchak in the Lower Volga region (self-settling salt) and the numerous group of Crimean lakes (pond salt). Lake salt comes in several varieties: lumpy salt - poorly purified salt for animal feed, granulated salt - very large and fairly pure salt, ground salt - coarse -"herring", fine -"table" and very fine -"ikra". Lake self-settling and pond salt accounts for about 45% of all T. s. extracted in the USSR. Rock salt is salt that has crystallized from the water of ancient seas that once covered the given area; its extraction is carried out in underground mines, more rarely rock salt deposits appear on the earth's surface. The main places of extraction are¹areas near Artemovsk and Ilepkaya Zashchita (near Orenburg). Rock salt accounts for up to 40% of all salt extracted in the USSR. Boiled salt is obtained by boiling salt solutions extracted in some areas from deep wells. The origin of underground salt solutions is explained by the action of soil waters on more or less deep deposits of rock salt. In addition, artificial leaching of rock salt deposits is practiced by introducing tap water into drill holes. The largest extraction of boiled salt is carried out in our country at the Perm and Slavyansk (former Kharkov province) salt works. The total amount of T. s. extracted by boiling constitutes about 7% of all salt extracted in the USSR. - In addition to the above methods of extracting T. s., at present in the USSR a project is being developed to obtain it from so-called sylvinite residues formed in huge quantities during the production of potassium salts in the Solikamsk region of the Urals. Sylvinite residues are very rich in NaCl and by proper purification, millions of tons of T. s. suitable for both food and technical purposes can be obtained. The main component of T. s. is sodium chloride, in addition it contains small amounts of impurities of calcium sulfate, magnesium sulfate, calcium chloride, magnesium chloride, potassium chloride, sodium sulfate, salts of iron and aluminum, as well as traces of bromine; sometimes very small amounts of salts of iodine, nitric, nitrous and boric acids are found. As accidental impurities, organic substances of plant and animal origin may be present in T. s. The chemical composition of T. s. varies depending on the place and method of its extraction. The best grades of edible T. s., obtained by recrystallization, are distinguished by great purity; they are called purified "table" salt. To purify ordinary salt, it is dissolved in water and, The sanitary assessment of T. s. is based on its degree of purity and dryness. Salt containing many impurities loses its good taste and becomes unsuitable for salting food and many household and technical purposes. The admixture of magnesium salts gives T. s. a bitter taste, the admixture of a large amount of calcium sulfate gives it an earthy taste. The presence of more than 1.5% KCl in T. s. causes a burning sensation in the mouth, sometimes nausea, weakness, etc. From the table above, it can be seen that in the salt extracted in the USSR, the KCl content is very small, a maximum of 0.12%. Such an amount does not noticeably change the taste of the salt. T. s. containing a large amount of alkaline earth salts greatly increases the hardness of the water in which food is cooked and thereby hinders the good boiling of such food products as meat, peas, beans, etc. According to the research of D. Tressler, an admixture of 1% CaCl₂ and MgCl₂ to table salt slows down its penetration deep into the fish during salting and makes the fish meat excessively tough. T. s. with a high CaS0₄ content is unsuitable for salting meat into salt meat, because such meat ferments weakly and therefore does not ripen well. The presence of iron in T. s. gives salted butter a bitter metallic taste. According to the requirements of the all-union standard (OST 616), edible T. s. must have the following qualities: 1) be white (shades of grayish, yellowish, pinkish are allowed depending on the origin of the salt), 2) have no odor, 3) have no visible mechanical impurities, 4) a 5% solution of salt should have a purely salty taste. The chemical composition for all grades of T. s., regardless of the place of its delivery and origin, is determined by the following standard norms when calculated on dry matter: sodium chloride (NaCl)-not less than 98%, total impurities-not more than 2%. For impurities included in the 2%, the following limits are established: 1) magnesium salts in terms of MgO-not more than 0.18%, 2) lime salts in terms of CaO-not more than 0.78%, 3) potassium salts in terms of K₂O-not more than 0.11%. T. s., _/ having a size of crystal aggregates not more than 0.8 mm, is called table salt; T. s., having a size of crystal aggregates not more than 2.5 mm, is called kitchen salt or ordinary salt; T. s., having a size of crystal aggregates not more than 4.5 mm, is called coarse salt. The moisture content in all grades of commercial table salt, regardless of its origin, should not exceed 3.5%.