152 SODIUM may be prepared by similar processes. The fluoride, NaF, exists in combination with alu- minic fluoride in the mineral cryolite 6(NaF), AUF., found in Greenland and the Ural, which is the chief source of metallic aluminum. (See An MIMM, and CRYOLITE.) Sodic sulphate, the well known Glauber's salt, is described un- der that title. Sodium unites with sulphurous acid to form a neutral and an acid sulphite. The neutral salt, Na 9 SO, + 10H a O, is procured by passing sulphurous anhydride (see SUL- PHUR), the product of sulphur burned in air, over moistened crystals of sodic carbonate as long as the gas is absorbed, dissolving the mass in water and crystallizing. It is extensively employed for the preparation of the hyposul- phite of soda, which is largely used under the name of "antichlor" to remove the last traces of chlorine from bleached paper pulp. (See P.vi'Kii, vol. xiii., p. 46.) The acid sulphite, NaHSOs, is of little importance. The hypo- sulphite, NaaSaOs + oHaO, was formerly made to some extent from impure sodic sulphide, or sulphuret of sodium, by passing sulphurous anhydride through it until it ceased to be ab- sorbed ; but it is now largely prepared from neutral sulphite of soda by digesting this salt with sulphuric acid for several days, at a mod- erate heat. It may also be prepared by digest- ing a solution of the sulphite with flowers of sulphur. The sulphur is gradually dissolved, forming a clear solution which yields crystals on evaporation; these are oblique prisms be- longing to the right prismatic system, free- ly soluble in water, but insoluble in alcohol. Hyposulphite of soda possesses the property of forming double salts with silver compounds, and in photography it is employed in dissolv- ing away ordinary insoluble compounds of sil- ver, such as chloride and iodide. A mixed solution of sulphite and hyposulphite of soda dissolves malachite and blue copper ore, and Stromeyer has employed it in the hydro-metal- lurgical extraction of copper. It is also used for preparing antimonial cinnebar and aniline green. Hyposulphite of soda fuses at compar- atively low temperatures in its water of crys- tallization, and advantage is taken of this prop- erty in the sealing of glass tubes containing explosive compounds to be used under water in torpedoes. Mr. M. Carey Lea employs it as a new test for ruthenium. If a salt of this metal is made alkaline with ammonia and boiled with the hyposulphite, it first acquires a rose color, and then a magnificent carmine. Employed in medicine, it appears to have de- oxidizing powers, in consequence, it has been suggested, of conversion of hyposulphurous into sulphurir acid. It diminishes urea and increases uric acid in the urine, and also in- creases the sulphates and causes the appear- ance of sugar and oxalic acid. It has been usi-d. in accordance with the suggestions of Dr. Polli, in zymotic diseases, or those which are supposed to be caused by ferments in the blood, the development of which it has the power of arresting. It has also been used in cases of yeasty vomiting, on account of its destructive effect on the sarcenia ventricttli which infests the stomach in that disease, and as a local application in parasitic affections of the skin and mucous membranes. It may be given in doses of from 10 to 20 grains three times a day, dissolved in -water. For external use a dram may be dissolved in an ounce of water. The nitrate, called also cubic nitre, is described in the article NITRATES. The neutral carbonate, commonly called soda in commerce, is treated under SODA. Bicar- bonate of soda, acid sodic carbonate, or mono- sodic carbonate, may be formed by saturating a strong solution of the neutral carbonate or sal soda with carbonic acid. It is also manu- factured on a large scale by passing a current of carbonic acid gas over crushed and moist- ened crystals of commercial carbonate, exposed two or three inches in depth in a chamber upon cloths stretched horizontally above one another. The carbonate passes into the ses- quicarbonate, and then into the bicarbonate, which may be redissolved and crystallized on evaporation in rectangular four-sided prisms, soluble in 10 parts of water at 50. If the so- lution is heated, four molecules of bicarbonate lose one of carbonic acid and are converted into the sesquicarbonate (4NaHC0 3 =2NaaCOs, HaCOs + HaCOs), which by heating to redness, or by continued boiling, is converted into nor- mal carbonate. Bicarbonate of soda is much used in medicine as an antacid and promoter of mucous secretions and perspiration, and as an ingredient in effervescing powders. (See EFFERVESCENCE.) It is also used in bread making, as was formerly the sesquicarbonate. There are several compounds of sodium with boracic acid, but only one is of any practical importance, the acid borate (biborate of soda, or common borax), which is described in the article BORAX. Sodium forms with the three varieties of phosphoric acid orthophosphates, metaphosphates, and pyrophosphates. Among the orthophosphates are trisodic phosphate, or subphosphate of sodium, NasPC^ + lSHaO, prepared from rhombic phosphate by adding caustic soda to its solution ; and the hydric disodic phosphate, or rhombic phosphate of sodium, NaaIIP04-f 12H 2 O, commonly called phosphate of soda, and the salt from which most of the phosphates are obtained. The latter is prepared by adding sodic carbonate to acid calcic phosphate, one of the salts formed in obtaining phosphorus. (See PHOSPHORUS, vol. xiii., pp. 464 and 465.) Tricalcic phos- phate is precipitated while the disodic phos- phate is held in solution. When decanted and evaporated it forms large, transparent, efflo- rescent, rhombic prisms, soluble in four parts of cold water, but fusing at 90 F. in their water of crystallization. It has an alkaline re- action, and corrodes flint glass, causing white silicious scales to separate from the surface. When evaporated at temperatures above 90
