Sodium, calcium metal preparation

Silver(II) oxide, 4 12 Silver oxynitrate, Ag70sN03, formation of, by silver(II) oxide, 4 13 Silver subfluoride, Ag2F, 6 18,19 Sodium, calcium metal preparation from a solution in, 6 18, 24... 

MetaHic potassium and potassium—sodium alloys are made by the reaction of sodium with fused KCl (8,98) or KOH (8,15). Calcium metal and calcium hydride are prepared by the reduction of granular calcium chloride with sodium or sodium and hydrogen, respectively, at temperatures below the fusion point of the resulting salt mixtures (120,121). 

Preparation. Sodium can be produced by electrolysis of a mixture of NaCl (40%) and calcium chloride, CaCl2 (60%), melting at about 580°C. The electrolysis is carried out as a melt in a Downs cell , producing also calcium metal as well, which is solidified in a collection pipe and returned back to the melt. Since 1950 a modified Downs cell has been used with an electrolyte consisting of a ternary mixture of NaCl, BaCl2 and CaCl2. 

Bulk holmium metal is prepared by reduction of holmium chloride or fluoride by sodium, calcium, or magnesium in a tantalum crucible under argon atmosphere ... 

Since the alkali metals as a class are the strongest chemical reducing agents known, they cannot be prepared by chemical reduction without trie enforcement of a heavy shift in equilibrium conditions as an example, small quantities of sodium metal may be prepared by reducing sodium chloride with calcium metal, distilling away the sodium metal as it is formed. 

The tetrahydroborate salts of alkali metals, M[BH4] (M = Li, Na, K),1 are important because they serve as starting materials for the preparation of other boron hydrides2,3 and because they are used frequently as reducing agents.4 The lithium and sodium salts are prepared on a technical scale.5 9 The tetrahydroborate salts of the alkaline earth metals, M[BH4]2 (M = Mg, Ca, Sr, Ba), have not as yet been used extensively however, calcium bis[tetrahydroborate(l-)], Ca(BH4)2,10 is very soluble in tetrahydrofuran (THF) and it therefore has considerable potential application as a substitute for the lithium and sodium salts. 

Technically, all signs seemed to point to metallic sodium for the production of potassium from its compounds as a step in the production of potassium superoxide. Sodium is commercially prepared by the electrolysis (I) of molten sodium chloride to which calcium chloride has been added to lower the melting point. The analogous process could not be used for potassium production (7) because the potassium will attack the graphite electrodes and because of the danger of explosion due to potassium carbonyl sometimes formed in the process. Rather than work on alternate electrodes of other material, a thermochemical process was developed, using the reduction of a potassium salt by sodium. Other processes (4) were investigated by Kraus. 

The laboratory preparation of the metal powder proceeds via reduction of the halides with sodium, calcium or CaHg. 

Addition of 1 mol of hydrogen to the carbon-carbon triple bond can be accomplished stereospecifically. Catalytic reduction leads to the cis isomer. This is most often carried out using Lindlar catalyst, a lead-poisoned palladium-on-calcium carbonate preparation. Palladium on BaS04 is an alternative. Some examples are recorded in Scheme 3.10. Numerous other catalyst systems have been employed to effect the same reduction. Many specific cases are cited in reviews of catalytic hydrogenations. If the trans alkene is desired, the usual method is a dissolving-metal reduction in ammonia. This reaction is believed to involve two successive series of reduction by sodium and protonation ... 

The principal commercial source of rubidium is accumulated stocks of a mixed carbonate produced as a byproduct in the extraction of lithium salts from lepidohte. Primarily a potassium carbonate, the byproduct also contains ca. 23 wt.% rubidium and 3 wt.% cesium carbonates. The primary difficulty associated with the production of either pure rubidium or pure cesium is that these two elements are always found together in nature and also are mixed with other alkali metals because these elements have very close ionic radii, their chemical separation encounters numerous issues. Before the development of procedures based on thermochemical reduction and fractional distillation, the elements were purified in the salt form through laborious fractional crystallization techniques. Once pure salts have been prepared by precipitation methods, it is a relatively simple task to convert them to the free metal. This is ordinarily accomplished by metallothermic reduction with calcium metal in a high-temperature vacuum system in which the highly volatile alkali metal is distilled from the solid reaction mixture. Today, direct reduction of the mixed carbonates from lepidolite purification, followed by fractional distillation, is perhaps the most important of the commercial methods for producing rubidium. The mixed carbonate is treated with excess sodium at ca. 650 C, and much of the rubidium and cesium passes into the metal phase. The resulting crude alloy is vacuum distilled to form a second alloy considerably richer in rubidium and cesium. This product is then refined by fractional distillation in a tower to produce elemental rubidium more than 99.5 wt.% pure. 

Calcium was first isolated by Sir Humphry Davy in 1808. Davy produced calcium amalgam by electrolyzing an aqueous solution of the chloride, CaCl, using a liquid-mercury cathode such as in the chlor-alkali process employing a mercury cathode. After distilling mercury from the amalgam formed, he obtained the pure calcium metal. His discovery showed lime to be an oxide of calcium. Later, Moissan reduced the calcium diiodide with sodium. The first industrial production of calcium metal was reported in 1904 and attributed to Brochers and Stockem, who prepared it by electrolysis of the molten chloride. This process was discontinued in 1940 and replaced by aluminothermic reduction of the oxide. 

Who do you suppose had a large hand in actually isolating the metals from these alkaline earths Who else but Sir Humphry Davy, fresh from his successful isolation of sodium and potassium. It turned out to be somewhat more difficult to isolate the 2A metals but, with the aid of work done by Berzelius and M. M. af Pontin, he was able, in 1808, to electrolyze moist lime in the presence of mercuric oxide to make an amalgam—that is, an alloy of mercury, which grudgingly yielded the silvery-white calcium metal. Today, calcium is prepared by the electrolysis of molten CaCl2 in the presence of Cap2 added to lower the melting point, as shown in Equation (13.2) ... 

The chromates of the alkali metals and of magnesium and calcium are soluble in water the other chromates are insoluble. The chromate ion is yellow, but some insoluble chromates are red (for example silver chromate, Ag2Cr04). Chromates are often isomorph-ous with sulphates, which suggests that the chromate ion, CrO has a tetrahedral structure similar to that of the sulphate ion, SO4 Chromates may be prepared by oxidising chromium(III) salts the oxidation can be carried out by fusion with sodium peroxide, or by adding sodium peroxide to a solution of the chromium(IIl) salt. The use of sodium peroxide ensures an alkaline solution otherwise, under acid conditions, the chromate ion is converted into the orange-coloured dichromate ion ... 

Rubidium can be liquid at room temperature. It is a soft, silvery-white metallic element of the alkali group and is the second most electropositive and alkaline element. It ignites spontaneously in air and reacts violently in water, setting fire to the liberated hydrogen. As with other alkali metals, it forms amalgams with mercury and it alloys with gold, cesium, sodium, and potassium. It colors a flame yellowish violet. Rubidium metal can be prepared by reducing rubidium chloride with calcium, and by a number of other methods. It must be kept under a dry mineral oil or in a vacuum or inert atmosphere. 

Organoperoxysulfonic acids and their salts have been prepared by the reaction of arenesulfonyl chlorides with calcium, silver, or sodium peroxide treatment of metal salts of organosulfonic acids with hydrogen peroxide hydrolysis of di(organosulfonyl) peroxides, RS(0)2—OO—S(02)R, with hydrogen peroxide and sulfoxidation of saturated, non aromatic hydrocarbons, eg, cyclohexane (44,181). 

Orthophosphate salts are generally prepared by the partial or total neutralization of orthophosphoric acid. Phase equiUbrium diagrams are particularly usehil in identifying conditions for the preparation of particular phosphate salts. The solution properties of orthophosphate salts of monovalent cations are distincdy different from those of the polyvalent cations, the latter exhibiting incongment solubiUty in most cases. The commercial phosphates include alkah metal, alkaline-earth, heavy metal, mixed metal, and ammonium salts of phosphoric acid. Sodium phosphates are the most important, followed by calcium, ammonium, and potassium salts. 

A large number of pyrophosphate salts have been prepared (Table 10). In addition to individual metal salts, ammonium pyrophosphates and many mixed-metal pyrophosphates are known. Pyrophosphates of notable commercial importance include sodium, potassium, and calcium salts. 

Sihca is reduced to siUcon at 1300—1400°C by hydrogen, carbon, and a variety of metallic elements. Gaseous siUcon monoxide is also formed. At pressures of >40 MPa (400 atm), in the presence of aluminum and aluminum haUdes, siUca can be converted to silane in high yields by reaction with hydrogen (15). SiUcon itself is not hydrogenated under these conditions. The formation of siUcon by reduction of siUca with carbon is important in the technical preparation of the element and its alloys and in the preparation of siUcon carbide in the electric furnace. Reduction with lithium and sodium occurs at 200—250°C, with the formation of metal oxide and siUcate. At 800—900°C, siUca is reduced by calcium, magnesium, and aluminum. Other metals reported to reduce siUca to the element include manganese, iron, niobium, uranium, lanthanum, cerium, and neodymium (16). 

Salt formation. The resin acids have a low acid strength. The pa s (ionization constants) values of resin acids are difficult to obtain, and values of 6.4 and 5.7 have been reported [23] for abietic and dehydroabietic acids, respectively. Resin acids form salts with sodium and aluminium. These salts can be used in detergents because of micelle formation at low concentrations. Other metal salts (resinates) of magnesium, barium, calcium, lead, zinc and cobalt are used in inks and adhesive formulations. These resinates are prepared by precipitation (addition of the heavy metal salt to a solution of sodium resinate) or fusion (rosin is fused with the heavy metal compound). 

Hydrogen can be prepared by the reaction of water or dilute acids on electropositive metals such as the alkali metals, alkaline earth metals, the metals of Groups 3, 4 and the lanthanoids. The reaction can be explosively violent. Convenient laboratory methods employ sodium amalgam or calcium with water, or zinc with hydrochloric acid. The reaction of aluminium or ferrosilicon with aqueous sodium hydroxide has also been used. For small-scale preparations the hydrolysis of metal hydrides is convenient, and this generates twice the amount of hydrogen as contained in the hydride, e.g. ... 

Step C Preparation ofthebase-A 300 ml one-necked, round-bottomed flask, equipped with a water-cooled condenser, calcium chloride tube and magnetic stirrer is charged with anhydrous methanol (150 ml) and sodium metal (5.75 g,0.25 g atom). When the reaction is complete, the solution is treated with dry guanidine hydrochloride (26.3 g, 0.275 mol) and stirred for 10 minutes. The sodium chloride that forms is removed by filtration. The solution is concentrated in vacuo to a volume of 30 ml and the residue treated with the product of Step B, heated one minute on a steam bath and kept at 25°C for 1 hour. The product is filtered, washed well with water, dissolved In dilute hydrochloric acid and the free base precipitated by addition of sodium hydroxide to give the amllorlde product base, a solid which melts at 240.5°-241.5°C. 

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