Stannic acid properties

Acidic Properties. As a typical acid, it reacts readily with alkaUes, basic oxides, and carbonates to form salts. The largest iadustrial appHcation of nitric acid is the reaction with ammonia to produce ammonium nitrate. However, because of its oxidising nature, nitric acid does not always behave as a typical acid. Bases having metallic radicals ia a reduced state (eg, ferrous and staimous hydroxide becoming ferric and stannic salts) are oxidized by nitric acid. Except for magnesium and manganese ia very dilute acid, nitric acid does not Hberate hydrogen upon reaction with metals. 

Of the tin additives studied, the anhydrous and hydrated zinc stannates, ZnSnO and ZnSn(OH), respectively, are considerably more effective flame-retardant synergists with the bromine present in the plastic than 8-stannic acid (Figure 1). In line with this observation, oxidic tin-zinc systems have previously been found to exhibit superior flame-retardant properties to tin oxides alone (19-22). In addition, ZnSnO, gives higher values of 01 than Sb20, incorporation levels studied, and, in fact, the 1% ZnSnO - containing plastics outperform samples containing 2% Sb O,. 

Tin(II) and Tm(IV) Hydroxides. Prepare tin (I I) and tin(IV) hydroxides in separate test tubes from solutions of tin chlorides. What reagent should be used to precipitate the tin hydroxides Do tin hydroxides exhibit amphoteric properties What tin compounds are known as a- and P-stannic acids How are they prepared Write the equations of the reactions. 

Preparation of a-Stannic Acid. Add a 10% ammonia solution to a tin(IV) chloride one up to complete precipitation. Wash the product with water by decantation until the chloride ions are removed and filter it off on a Buchner funnel. Test the reaction of a-stannic acid with water, acids, and alkalies. Do the properties of this acid remain the same after prolonged standing or boiling Perform the relevant experiments. 

Properties oe-stannic acid, DTA results available, BET specific surface area 153 mVg [1660]. 

Jaffrezic-Renault, N. et al.. Study of the amphoteric properties of a-stannic acid, Radiochem. Radioanal. Lett., 37, 257, 1979,... 

Discussion As in the case of other elements recently studied, a knowledge of the reaction of its hydroxides is important in summarizing the properties of tin in respect to its electropositive or electronegative characteristics. The position of tin in the fourth group of the periodic classification would lead to the prediction of distinctly acidic properties for stannic hydroxide, yet the fact that tin occurs so far down as the sixth member of the group would indicate the possibility of some basic characteristics. 

The property that stannic acid has of preventing the precipitation of many oxides such as those of bismuth, copper, lead, etc., and likewise the precipitation of phosphoric acid, is well known in analytical chemistry. 

Smith changed the definitions somewhat in reviewing his work with selenium oxychloride as a solvent. He found that stannic, ferric, silicon, arsenious, and titanium chlorides and sulfur trioxide displayed typical acid properties in selenium oxychloride. He defined an acid as an electron-pair acceptor toward the solvent, and a base as an electron-pair donor toward the solvent. These definitions, suggested in 1938, were the first to show the influence of the proposals made by Lewis in 1923. 

Zoltai, T., and M. J. Buerger, 1960. The relative energies of rings of tetrahedra. Z. Krist. 114 1. Zsigmondy, R., 1914. Influence of the quantity of peptising agent on the properties of hydrosols. Hydrosols of stannic acid. Z. Anorg. Chem. 89 210. 

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). 

To the remainder of the precipitate add 5 c.c. of concentrated hydrochloric acid and heat to boiling. (6) What happened (7) Kef erring to the properties of the sulphides of arsenic studied in Experiment 89, state how stannic sulphide may be distinguished from them. 

Within the context of the acorane-cedrane type compounds it was noted that Demole et al. had identified the unusual oxetan compound (132) in the stannic chloride-promoted cyclization of (131). This compound appears to be an obvious candidate for conversion into carotol (165). However, it would appear that efforts to effect this conversion have not yet met with success. Naegeli and Kaiser also made the interesting observation that acid-catalysed cyclization of the diene-ol (158) (see Scheme 12) yielded, as the major product, a hydrocarbon whose spectral properties were identical with those of( + )-daucene (160and 164). The above result was almost simultaneously communicated by Yamasaki, who... 

Lewis Acids. Lewis acids, eg, boron trihalides, contain an empty outer orbital and therefore seek reaction with areas of high electron density. Boron trifluoride, BF3, a corrosive gas, reacts easily with epoxy resins, causing gelation within a few minutes. Complexation of boron trihalides with amines enhances the curing action. Reasonable pot lives using these complexes can be achieved because elevated temperatures are required for cure. Reactivity is controlled by the choices of the halide and the amine. The amine choice also affects other properties such as solubility in resin and moisture-sensitivity. Boron trifluoride monoethylamine (BF3 NH2C2H5), a crystalline material which is a commonly used catalyst, cures epoxy resins at 80-100°C. A chloride version is also commercially available. Other Lewis acids used in epoxy curing include stannic chloride and tin octanate. 

Graham s iron oxide differs from the meta variety in that the former is more stable and its precipitate is more soluble in acids. Colloidal iron oxide on the market has properties that lie between these two extremes. It is precipitated by moderately concentrated HCl but the solid gradually goes into solution again to form a chloride. This colloid therefore bears the same relation to Graham s and raetairon oxide that colloidal stannic oxide prepared by the author s method bears to the ct and p varieties. 

Phenol and its derivatives are known to form phthaleins with phthalic anhydrides and the products are very well known acid-base indicators. With maleic anhydride, a variety of phenols have been examined by Webster and Kamstra, including halogenated phenols and aminophenols while using anhydrous stannic chloride and sulfuric acid as catalysts. Although indicator properties of some were shown, no rigorous structure proof or yield data were given. Maleins 146 were reported to have formed. 

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