Stannic oxide

Stannic oxide heated to 200 C 0-088 Carbon tetrachloride 0-085 Carbon tetrachloride 14... 

Fig. 4.25 Adsorption isotherms showing low-pressure hysteresis, (a) Carbon tetrachloride at 20°C on unactivated polyacrylonitrile carbon Curves A and B are the desorption branches of the isotherms of the sample after heat treatment at 900°C and 2700°C respectively Curve C is the common adsorption branch (b) water at 22°C on stannic oxide gel heated to SOO C (c) krypton at 77-4 K on exfoliated graphite (d) ethyl chloride at 6°C on porous glass. (Redrawn from the diagrams in the original papers, with omission of experimental points.)...

Parameter Zinc hydroxy staimate Zinc staimate Stannic oxide... 

Copper and tin phosphides are used as deoxidants in the production of the respective metals, to increase the tensile strength and corrosion resistance in phosphor bronze [12767-50-9] and as components of brazing solders (see Solders and brazing alloys). Phosphor bronze is an alloy of copper and 1.25—11 wt % tin. As tin may be completely oxidized in a copper alloy in the form of stannic oxide, 0.03—0.35 wt % phosphoms is added to deoxidize the alloy. Phosphor copper [12643-19-5] is prepared by the addition of phosphoms to molten copper. Phosphor tin [66579-64-4] 2.5—3 wt % P, is made for the deoxidation of bronzes and German silver. 

K. Ihokura and J. Watson, The Stannic Oxide Gas Sensor, CRC Press, Ann Arbor, Mich., 1994. 

Tin does not react directly with nitrogen, hydrogen, carbon dioxide, or gaseous ammonia. Sulfur dioxide, when moist, attacks tin. Chlorine, bromine, and iodine readily react with tin with fluorine, the action is slow at room temperature. The halogen acids attack tin, particularly when hot and concentrated. Hot sulfuric acid dissolves tin, especially in the presence of oxidizers. Although cold nitric acid attacks tin only slowly, hot concentrated nitric acid converts it to an insoluble hydrated stannic oxide. Sulfurous, chlorosulfuric, and pyrosulfiiric acids react rapidly with tin. Phosphoric acid dissolves tin less readily than the other mineral acids. Organic acids such as lactic, citric, tartaric, and oxaUc attack tin slowly in the presence of air or oxidizing substances. 

Of the large volume of tin compounds reported in the Hterature, possibly only ca 100 are commercially important. The most commercially significant inorganic compounds include stannic chloride, stannic oxide, potassium staimate, sodium staimate, staimous chloride, stannous fluoride, stannous fluoroborate, stannous oxide, stannous pyrophosphate, stannous sulfate, stannous 2-ethyUiexanoate, and stannous oxalate. Also important are organotins of the dimethyl tin, dibutyltin, tributyltin, dioctyltin, triphenyl tin, and tricyclohexyltin families. 

Stannic and stannous chloride are best prepared by the reaction of chlorine with tin metal. Stannous salts are generally prepared by double decomposition reactions of stannous chloride, stannous oxide, or stannous hydroxide with the appropriate reagents. MetaUic stannates are prepared either by direct double decomposition or by fusion of stannic oxide with the desired metal hydroxide or carbonate. Approximately 80% of inorganic tin chemicals consumption is accounted for by tin chlorides and tin oxides. 

Stannic Oxide. Stannic oxide tin(IV) oxide, white crystals, mol wt 150.69, mp > 1600° C, sp gr 6.9, is insoluble in water, methanol, or acids but slowly dissolves in hot, concentrated alkaH solutions. In nature, it occurs as the mineral cassiterite. It is prepared industrially by blowing hot air over molten tin, by atomizing tin with high pressure steam and burning the finely divided metal, or by calcination of the hydrated oxide. Other methods of preparation include treating stannic chloride at high temperature with steam, treatment of granular tin at room temperature with nitric acid, or neutralization of stannic chloride with a base. 

Other important uses of stannic oxide are as a putty powder for polishing marble, granite, glass, and plastic lenses and as a catalyst. The most widely used heterogeneous tin catalysts are those based on binary oxide systems with stannic oxide for use in organic oxidation reactions. The tin—antimony oxide system is particularly selective in the oxidation and ammoxidation of propylene to acrolein, acryHc acid, and acrylonitrile. Research has been conducted for many years on the catalytic properties of stannic oxide and its effectiveness in catalyzing the oxidation of carbon monoxide at below 150°C has been described (25). 

Transparent electroconductive coatings of stannic oxide are deposited on nonconductive substrates for electrical and strengthening appHcations. However, the agents used to deposit the oxide film are actually stannic chloride. More recently, some organotin compounds have been employed. 

Hydrated Stannic Oxide. Hydrated stannic oxide of variable water content is obtained by the hydrolysis of stannates. Acidification of a sodium stannate solution precipitates the hydrate as a flocculent white mass. The colloidal solution, which is obtained by washing the mass free of water-soluble ions and peptization with potassium hydroxide, is stable below 50°C and forms the basis for the patented Tin Sol process for replenishing tin in staimate tin-plating baths. A similar type of solution (Staimasol A and B) is prepared by the direct electrolysis of concentrated potassium staimate solutions (26). 

Soluble Sta.nna.tes, Many metal staimates of formula M Sn(OH) are known. The two main commercial products are the soluble sodium and potassium salts, which are usually obtained by recovery from the alkaline detinning process. They are also produced by the fusion of stannic oxide with sodium hydroxide or potassium carbonate, respectively, followed by leaching and by direct electrolysis of tin metal in the respective caustic solutions in cells using cation-exchange membranes (27). Another route is the recovery from plating sludges. 

Potassium staimate, K2Sn(OH) (mol wt 298.93), and sodium stannate [12058-66-17, Na2Sn(OH), mol wt 266.71, are colorless crystals and are soluble in water. The solubiUty of potassium stannate in water is 110.5 g/100 mL water at 15°C and that of sodium stannate is 61.5 g/100 mL water at 15°C. The solubihty of sodium stannate decreases with increasing temperature, whereas the solubiUty of potassium stannate increases with increasing temperature. The solubihty of either sodium or potassium stannate decreases as the concentration of the respective free caustic increases. Hydrolysis of stannates yields hydrated stannic oxides and is the basis of the Tin Sol solution, which is used to replenish tin in stannate tin-plating baths (28,29). 

The inorganic tin compound that has received the most study from a toxicological viewpoint is stannic oxide. Autopsies performed on workers in the tin mining and refining industry, who inhaled tin oxide dust for as long as 20 yr, disclosed no pulmonary fibrosis (57). Inhalation for long periods produces a benign, symptomless pneumoconiosis with no toxic systemic effects (58). 

Other studies of the toxicity of stannous fluoride, sodium pentafluorostannite, sodium pentachlorostannite, sodium chlorostannate, stannous sulfide [1314-95-0] stannous and stannic oxides, stannous pyrophosphate [15578-26 ] stannous tartrate [815-85-0] and other inorganic tin compounds are reviewed in References (dh—12. The OSHA TLV standard for inorganic tin compounds is two milligrams of inorganic tin compounds as tin per cubic meter of air averaged over an eight-hour work shift (47). 

Stannic oxide (Sn02) [18282-10-5] M 150.7, m 1630°, d 6.95. Refluxed repeatedly with fresh HCl until the acid showed no tinge of yellow. The oxide was then dried at 110°. 

Stanni-ozyd, n, stannic oxide, tin(IV) oxide, -reihe, /. stannic series, tin(IV) series, -salz, n. stannic salt, tin(IV) salt, -sulfo-zyanid, n. stannic thiocyanate, tin(IV) thiocyanate. -verbindung, /, stannic compound, tin(IV) compound,... 

Zinn-asche, /. tin ashes, stannic oxide, -dtzfarbe, /. (Cali o) tin discharge paste, -bad, n. tin bath, -beize, /. tin mordapt, tin spirit, -beizendruck, m. tin ordant printing, -bergwerk, n. tin mine, -blatt, fu tin foil. n. tin. plate, sheet tin. 

In propellants (see Propellants, Solid in this Vol), some of the work reported by Dunkle (Ref 6) examined the addn of flash reducing agents versus smoke evolved in propint compns for the cal. 50 rifle. The oxides examined included aluminum oxide, stannic oxide, silicon dioxide, ferric oxide and, after proplnt ignition, nickel... 

Stannic Oxide (White Tin Oxide, Tin Dioxide, Stannic Anhydride, Flowers of Tin Stannic Acid, Cassiterite). Sn02, mw 150.69, white powd, mp 1127°, bp 1800-1900° (subl), d 6.95 g/cc. Sol in coned sulfuric and coned hydrochloric acids, si sol in hot coned aq KOH or NaOH. Prepn is by reacting Sn with coned nitric acid (d 1.41 g/cc) on a w bath forming 0-stannic acid. The 0-stannic acid is then heated to a red heat and converted to Sn02. It is used as a chemical reagent and (see above) as an antifouling, flash and barrel wear reducing additive in propints... 

Dimethyltin dichloride is used in the glass industry as an alternative to stannic chloride for coating glass with a thin film of stannic oxide 562). The dialkyltin compound vapor is brought into contact with the glass surface at temperatures of 500-600°C, where decomposition and oxidation occurs. 

Whereas stannic oxide is neither oxidizing nor reducing, plumbic oxide is a powerful oxidizer. 

Tin, which is present in the ore as stannic oxide (Sn02), does not chlorinate under these conditions ... 

Aluminium oxide, arsenic trioxide, bismuth trioxide, calcium oxide, chromic oxide, lanthanum oxide, lead dioxide, magnesium oxide, manganese dioxide, molybdenum trioxide, phosphorus pentoxide, stannic oxide, sulfur dioxide (explodes), tantalum pentoxide, tungsten trioxide, vanadium pentoxide. 

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