Sulphite alternatives

Alternatively these salts can be prepared by first saturating a known volume of alkali with sulphur dioxide, giving a solution of the hydrogensulphite, from which sulphite can be prepared by the addition of a second equal volume of alkali. 

Alternatively, the iodide is precipitated as copper(I) iodide by addition of copper(II) sulphate, in presence of sulphite, thus ... 

Alternatively cellulose is produced from wood via wood pulp. A number of processes are used in which the overall effect is the removal of the bulk of the non-cellulosic matter. The most widely used are the sulphite process, which uses a solution of calcium bisulphite and sulphur dioxide, the soda process using sodium hydroxide and the sulphate process using a solution of sodium hydroxide and sodium sulphide. (The term sulphate process is used since sodium sulphate is the source of the sulphide.) For chemical purposes the sulphite process is most commonly used. As normally prepared these pulps contain about 88-90% alpha-cellulose but this may be increased by alkaline purification and bleaching. 

Constitution.—As with sulphurous acid and the sulphites, a decision is necessary between alternative formula for selenious acid and the selenites, the possible structures being the symmetrical xOH CL /OH... 

An alternative means of preparation of a solution of copper(i) bromide involves heating under reflux a mixture of 63 g (0.25 mol) of copper(n) sulphate pentahydrate, 20g (0.314mol) of copper turnings, 114g (1.109mol) of sodium bromide, 30 g (16.3 ml) of concentrated sulphuric acid and 1 litre of water for 3-4 hours. If the colour of the solution has not become yellowish after this period of heating, a few grams of sodium sulphite should be added to complete the reduction. 

Note. (1) In an alternative procedure,11 iodine (3.8 g, 15 mmol) is dissolved in benzene (50 ml), to this solution is added a mixture of anhydrous aluminium chloride (4.0 g, 30 mmol) and copper(n) chloride (4.0 g, 30 mmol) previously dried at 120°C/3mmHg for more than 3 hours. The mixture is stirred at 40 °C for 2 hours, and then poured into water. The organic layer is washed with aqueous sodium hydrogen sulphite, dried and fractionally distilled. The yield of iodobenzene is 79 per cent. 

The test is usually carried out by adding the reagent to the solution acidified with dilute hydrochloric acid carbonates, sulphites, and phosphates are not precipitated under these conditions. Concentrated hydrochloric acid or concentrated nitric acid should not be used, as a precipitate of barium chloride or of barium nitrate may form these dissolve, however, upon dilution with water. The barium sulphate precipitate may be filtered from the hot solution and fused on charcoal with sodium carbonate, when sodium sulphide will be formed. The latter may be extracted with water, and the extract filtered into a freshly prepared solution of sodium nitroprusside, when a transient, purple colouration is obtained (see under Sulphides, Section IV.6, reaction 5). An alternative method is to add a few drops of very dilute hydrochloric acid to the fused mass, and to cover the latter with lead acetate paper a black stain of lead sulphide is produced on the paper. The so-called Hepar reaction, which is less sensitive than the above two tests, consists of placing the fusion product on a silver coin and moistening with a little water a brownish-black stain of silver sulphide results. 

Vivas et al. 1997). Recently, the evaluation of the dual antioxidant and antibacterial activity of 21 phenolic compounds mainly present in Vitis Vinifera L. belonging to different groups was examined (Garcfa-Ruiz et al. 2008b). Structure-activity relationships were probed for both antimicrobial and antioxidant properties of wine phenolics, confirming the potential of these compounds as an alternative to sulphites in winemaking. 

J.J. Garceau, S.N. Lo, and L. Marchildon, A Cost Evaluation of Alternative Sulphite Spent Liquor Strategies. Pulp Pap. Can. 77(10), T174 (1976). 

Sulphur dioxide gas. This gas is available commercially in a liquefied state in aluminium canisters, from which it can be taken. Alternatively it can be produced from sodium sulphite and 8m sulphuric acid. The solid reagent should be placed into a round-bottomed flask, which can be heated. The acid is kept in a funnel with a stopcock, inserted into one opening of the flask. By adding some sulphuric acid to the solid and by gentle heating, sulphur dioxide gas comes through the second opening of the flask and can be washed in concentrated sulphuric acid. 

The demand for hafnium metal is small. Figure 9.7 shows how it can be obtained in a high state of purity as a by-product from the manufacture of zirconium. The conversion of the pure by-product solution to oxide is via sulphite as in the case of zirconium, and similarly several alternative precipitants would each be satisfactory. The Van Arkel iodide decomposition process has been shown, in its cheapest form, i.e. based upon a carbide feed. Either of the two metal-producing stages shown for zirconium are equally applicable. 

In sulphur dioxide oxidation cells the prevention of deactivation of the cathode by sulphur formed by cathodic reduction of sulphite can be a problem. A solution to this is to use a cathode material less sensitive to sulphur (or H2S) formation such as tungsten carbide [49]. An alternative cathode material to be used in this context is Ebonex [50]. 

Molasses, whey, sulphite liquors and potato wastes all have been utilized successfully over the past few years. However, the alternate uses for molasses for direct animal feeding, citric acid or alcohol production have made it available only at a price. In many cases this price has been too high to justify economic exploitation. 

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