SODA POWDERS SODIUM 151 soap, for which purpose it is better adapted than potash on account of not being deliques- cent like the latter alkali (see SOAP) ; and also very largely in the preparation of paper pulp from various materials. The paper maker uses it in connection with quicklime, which reduces it to caustic soda. (See PAPER.) It is also used in the laundry, and for domestic and cleansing purposes generally. SODA POWDERS. See EFFERVESCENCE. SODA WATER. See MINERAL WATERS. SODERM LVLAM), a S. E. Igen or province of Sweden, bounded N. by Lake Maslar, E. by the lasn of Stockholm, which embraces a portion of the old province of Sodermanland, and 8. E. by the Baltic; area, 2,603 sq. m. ; pop. in 1874, 138,696. It is generally level and fer- tile, and abounds in inland lakes, including part of Lake Hjelmar. Agriculture is the principal occupation, and the fisheries and lumber trade are of some importance. Capi- tal, ISTykoping. SODIUM, the most abundant of the alkali met- als, its chloride composing the principal part of the saline matter of the ocean, and also ex- isting in extensive beds in geological strata. Large quantities of nitrate and carbonate of sodium are found in beds, and in some rocks it is combined with silica. The metal was ob- tained by Sir Humphry Davy soon after his discovery of potassium, and by a similar meth- od. Gay-Lussac and Thenard afterward pre- pared it by decomposing sodic hydrate with metallic iron at a white heat. It may be pre- pared readily by the process of Brunner, which consists in distilling a mixture of the carbonate with powdered charcoal. The process has been improved by Deville and others, and em- ployed on a large scale in manufacturing. The carbonate of soda used in the process is pre- pared by calcining the crystallized neutral car- bonate. It is thoroughly dried, pounded, and mixed with a slight excess of charcoal. Ground chalk is also added, to preserve a. pasty condi- tion and prevent the carbonate of soda from separating from the charcoal. The following proportions are recommended by Deville for manufacturing operations: dry carbonate of soda, 30 kilogrammes; charcoal, 13; chalk, 3. The materials should be thoroughly mixed, and it is well to calcine the mixture before patting it into the distilling apparatus, by which it is made more compact, so that a greater quan- tity can be introduced. It is put into cylindri- cal iron retorts covered with clay, which are heated in a reverberatory furnace. The re- torts have movable ends, so that at the close of the operation the charge may be withdrawn and a fresh one introduced without removing the cylinders or putting out the fire. The re- ceivers are of the form used in the preparation of potassium. (See POTASSIUM, vol. xiii., p. 758.) The same precautions are necessary as in the preparation of that metal. The chalk is employed to prevent the charcoal from sep- arating the carbonate of soda when it fuses. The charcoal combines with oxygen when the heat is sufficient to weaken the affinities be- tween the constituents of the salt, and the metallic sodium is left free, when it distils over and is condensed in the receiver, nearly pure if the operation is well conducted. It is perfectly purified by melting it under naphtha, when it may be run into moulds like those used for lead. Sodium is a brilliant silver-white metal, resembling potassium in its physical and in most of its chemical properties. It is a good conductor of heat and electricity. Its specific gravity is 0'972, its atomic weight 23, and its symbol Na (natrium). It is soft at common temperatures, fuses at 207'7 F., and oxidizes rapidly in the air. At the freezing point of water it is very ductile, and at the zero of Fahrenheit it is quite hard. If a small quan- tity of the metal is melted in a sealed tube filled with coal gas, and cooled till crystalliza- tion begins, when the liquid portion is turned off shining octahedral crystals will remain. When dropped into cold water it decomposes it with violence, evolving hydrogen gas, but does not produce enough heat to inflame it unless the metal is held in one spot so that the heat shall not be dissipated. If the water is previously warmed, the gas will take fire, burn- ing with a bright characteristic yellow flame. Sodium is widely diffused in the mineral, ani- mal, and vegetable kingdoms, united with silicic and carbonic acid in many minerals, forms a large share of the saline portions of animal flu- ids, and enters largely into the composition of marine plants. It unites with oxygen to form two well known oxides : the monoxide, Na 2 O, the soda of the chemists, and the dioxide, NaaOa. These two oxides are formed when sodium is burned in common air. When burned in oxy- gen gas till it no longer increases in weight, it is wholly converted into the dioxide. With water it forms a hydrate, NaHO, which corre- sponds in composition to the monoxide, a mole- cule of hydrogen replacing one of sodium. This hydrate is the caustic soda of commerce. (See SODA.) Salts. The salts of sodium are among the most important of all compounds, not ex- cepting those of potassium. The principal one is the chloride, or common salt. (See SALT.) The iodide, Nal, and the bromide, NaBr, are anal- ogous to the corresponding potassium com- pounds. At temperatures above 86 the bro- mide crystallizes in anhydrous cubes, but at lower temperatures it unites with two mole- cules of water and forms hexagonal tables. The iodide, at temperatures above 104, crystallizes in anhydrous cubes ; but at ordinary tempera- tures large, transparent, striated, oblique rhom- bic prisms are formed, containing two molecules of water. The small proportion of sodic iodide which is contained in sea water furnishes the commercial supply of iodine, the kelp from which iodine is obtained being the ashes of marine plants which assimilate the iodide from the sea water. (See IODINE.) The sulphides of sodium correspond to those of potassium, and
