Antimonates

Antimony penioxide, Sb20j, is yellow (Sb plus cone. HNO3). Decomposes to Sb02 on heating. Gives antimonates(V) with alkalis. Used as a flame retardant. 

Crude lead contains traces of a number of metals. The desilvering of lead is considered later under silver (Chapter 14). Other metallic impurities are removed by remelting under controlled conditions when arsenic and antimony form a scum of lead(II) arsenate and antimonate on the surface while copper forms an infusible alloy which also takes up any sulphur, and also appears on the surface. The removal of bismuth, a valuable by-product, from lead is accomplished by making the crude lead the anode in an electrolytic bath consisting of a solution of lead in fluorosilicic acid. Gelatin is added so that a smooth coherent deposit of lead is obtained on the pure lead cathode when the current is passed. The impurities here (i.e. all other metals) form a sludge in the electrolytic bath and are not deposited on the cathode. 

Antimony forms both a + 3 and a + 5 oxide. The + 3 oxide can be prepared by the direct combination of the elements or by the action of moderately concentrated nitric acid on antimony. It is an amphoteric oxide dissolving in alkalis to give antimonates(III) (for example sodium antimonite , NaSb02), and in some acids to form salts, for example with concentrated hydrochloric acid the trichloride, SbCl3, is formed. 

No +3 acid is known for antimony but antimonates(III) (anti-monites) formed by dissolving antimony(IIl) oxide in alkalis are known, for example sodium dioxoantimonate(III), NaSb02. 

The + 5 acid is known in solution and antimonates(V) can be obtained by dissolving antimony(V) oxide in alkalis. These salts contain the hexahydroxoantimonate(V) ion, [Sb(OH)(,] . 

This is a simplified formula for tartar emetic, for X-ray crystal analysis and infrared studies indicate that the. Sb is a part of the antimonate anion [Sb(OH)4] and forms part of a cyclic system. 

When immediately followed by -in or -ine, phospha- should be replaced by phosphor-, arsa- by arsen-, and stiba-by antimon-. The saturated six-membered rings corresponding to phosphorin and arsenin are named phosphorinane and arsenane. A further exception is the replacement of borin by borinane. 

Exceptions to the use of the root name of the central atom are antimonate, bismuthate, carbonate, cobaltate, nickelate (or niccolate), nitrate, phosphate, tungstate (or wolframate), and zincate. 

Potassium acid antimonate, KH2Sb04—Q.IN boil 23 g of the salt with 950 mL of water for 5 minutes, cool rapidly and add 35 mL of 6N KOH allow to stand for one day, filter dilute filtrate to a liter. 

Fig. 3. Mechanism of selective ammoxidation and oxidation of propylene over antimonate catalysts (31).

Table 2. Properties of Antimony Pentoxide and Sodium Antimonate...

Sodium Antimonate. Sodium antimonate [15593-75-6] Na SbO, another antimony synergist of commercial importance, has an antimony content of 61—63 wt % and a bulk density of 39.4—46.4 kg/m. Properties are given in Table 2. It is made by oxidizing antimony trioxide using sodium nitrate and caustic. It is a white powder and has a pH of around 9—11 when dissolved in water. 

Sodium antimonate contains less antimony than either antimony trioxide or pentoxide and is thus less effective. However, its unique pH and low refractive index makes the antimonate the most desirable synergist for polymers that hydrolyze when processed with acidic additives or in polymers for which deep color tones are specified. Sodium antimonate costs approximately 3.30—4.40/kg and can be obtained from either Elf Atochem NA under the Thermoguard name or from Anzon Inc. as a Timinox product. 

The niter and fresh caustic soda, required to maintain the fluidity of the salt bath in the reactor chamber, are added gradually. When the color of the saturated salts turns from a dark gray to white, the impurity metals are at their highest state of oxidation, and the lead content of the spent salts is very low. In a modification, the arsenic and tin are selectively removed as sodium arsenate and sodium stannate, followed by the removal of antimony as sodium antimonate. 

Wet Process. The sodium arsenate and stannate slag are treated by a leach and precipitation process to produce calcium arsenate, calcium stannate, and a sodium hydroxide solution for recycle. The sodium antimonate filtercake containing selenium, tellurium, and indium is treated in a special metals refinery to recover indium and tellurium. 

Lead antimonate [13510-89-9] (Naples yellow), Pb2(Sb0 2> mol wt 993.07, d = 6.58g/cm, is an orange-yeUow powder that is insoluble in water and dilute acids, but very slightly soluble in hydrochloric acid. Lead antimonates are modifiers for ferroelectric lead titanates, pigments in oil-base paints, and colorants for glasses and glazes (see Colorants for ceramics). They are made by the reaction of lead nitrate and potassium antimonate solutions, followed by concentration and crystallization. 

By-Product and Secondary Antimony. Antimony is often found associated with lead ores. The smelting and refining of these ores yield antimony-hearing flue, baghouse, and CottreH dusts, drosses, and slags. These materials may be treated to recover elemental antimony or antimonial lead from which antimony oxide or sodium antimonate may be produced. 

Antimony Compounds. The greatest use of antimony compounds is in flame retardants (qv) for plastics, paints, textiles, and mbber. Antimony compounds used in flame retardants are antimony pentoxide, sodium antimonate [15593-75-6] Na[Sb(OH) ], and, most importantly, antimony trioxide. These compounds, when used alone, are poor flame retardants however, when combined with halogen compounds, they produce mixtures that are effective. 

Antimony trioxide and sodium antimonate are added to specialty glasses as decolorizing and fining agents, and are used as opacifiers in porcelain enamels. Antimony oxides are used as white pigments in paints, whereas antimony trisulfide and pentasulfide yield black, vermilHon, yeUow, and orange... 

H. Quiring, Die Metallischen Kohstoffe Vol. 7, Antimon Eetdinand Enke, Stuttgart, Germany, 1945. 

Antimony trioxide is insoluble in organic solvents and only very slightly soluble in water. The compound does form a number of hydrates of indefinite composition which are related to the hypothetical antimonic(III) acid (antimonous acid). In acidic solution antimony trioxide dissolves to form a complex series of polyantimonic(III) acids freshly precipitated antimony trioxide dissolves in strongly basic solutions with the formation of the antimonate ion [29872-00-2] Sb(OH) , as well as more complex species. Addition of suitable metal ions to these solutions permits formation of salts. Other derivatives are made by heating antimony trioxide with appropriate metal oxides or carbonates. 

Antimonic acid has been used as an ion-exchange material for a number of cations in acidic solution. Most interesting is the selective retention of Na" in 12 Af HQ, the retention being 99.9% (24). At lower acidities other cations are retained, even K". Many oxidation and polymerization catalysts are listed as containing Sb203. 

Meglumine [6284-40-8] antimonate [133-51 -7] C H NO HO Sb, (Glucantime) is a pentavalent antimonial used for the treatment of leishmania sis in Latin America (207) and in the French-speaking areas of Europe and Africa (206). It is adrxiinistered by deep intramuscular injection. Although relatively safe and usually well tolerated, numerous side effects have been observed. It is not available in the United States. 

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