Sulphuric anhydride

In SL-PC, a catalyst is supported on a solid matrix in the form of the film of a nonvolatile liquid phase adsorbed on the solid. The catalytic film can be, for example, a molten salt or a molten oxide (e.g., Deacon s catalyst (CUCI2/KCI) used to oxidize HCl with oxygen for the chlorination of ethylene in the synthesis of vinyl chloride. Figure 6.1 V2O5 for the oxidation of sulphurous to sulphuric anhydride). Alternately, it can be a liquid phase (e.g., ethylene glycol, PPh3, butyl benzyl phthalate, etc.) that contains a soluble catalytic species such as a metal complex. 

Two atoma of nitrogen and three atoms of oxygen tbrm nitrons anlurdride. One atom of sulphur and three atoms of rn gea form sulphurto anhydride One atom of sulphur and two atoms of oxygen form sulphurous anhydride. 

Seaafion.— The hyposulphites, when acted upon by acids, erolve sulphurous anhydride, whilst sulphur is precipitoted —... 

This acid is obtained by the action of hydro sulphuric acid on sulphurous anhydride —... 

Sulphurous anhydride, when passed into solutions of the metallio hydrates, produces sulphites. If the sulphurous anhy dride be in excess, an acid sulphite is obtmned —... 

Sulphites are recognised by the pungent odour of sulphurous anhydride which they evolve on the addition of a strong acid, such as sulphuric acid —... 

Mahmiar teeight a 80. Molecular volmte CD- 1 Hire sulphuric anhydride vapour teeighs 40 criths. Fuses at 24 -6. Boils at 621. ... 

Preparation,—1. By passing a mixture of sulphurous anhydride and oxygen over ignited spongy platinum... 

Dhe nitric oxide by the action of oxygen reproduces nitric peroxide, which is then ready to undergo the same processes a second time. The nitric acid is at the same time reduced to nitric peroxide by the action of sulphurous anhydride —... 

Starting from sulphuric anhydride and ammonia the following series of reactions was employed ... 

This mixture was prepared from 99% nitric acid and sulphuric anhydride. White salt (XVIII) was introduced to the mixture at a temperature of 30°C. The heat evolved during nitration (approximately 500 kcal per kg of cyclonite) was removed by means of a cooling coil. The cyclonite so formed was partly suspended and partly dissolved in the nitrating liquid. Addition of water completely precipitated the product which was separated on a vacuum filter. The composition of the spent acid was ... 

Historical.—The first mention of sulphur trioxide is by Basil Valentine at the end of the fifteenth century. The method of formation by heating ferrous sulphate was first described in 1675 by Lemery, whilst the preparation by heating fuming sulphuric acid was discovered a century later by Bernhardt. Scheele and Guyton de Morveau first recognised the compound as sulphuric anhydride. 

Sulphur dioxide is oxidised by the heptoxide with formation of sulphuric anhydride ... 

Imidosulphonic Acid, NH(S03H)2, the amide of which has already been described (p. 242), may be obtained as the ammonium salt by mixing sulphuric anhydride vapour with excess of gaseous ammonia and fusing the condensed flocculent product in an atmosphere of ammonia ... 

It may also be obtained by the action of nitrosyl chloride on sulphuric anhydride. It is a -white, leafy, crystalline mass, somewhat resembling stearic acid in appearance. It is decomposed by moist air with formation of sulphuric, hydrochloric and nitric acids.1... 

Hydrazine Ditfaionate, N2H4.H2S2Oa, a polymer of amidosul-phonic acid, may be prepared by the interaction of hydrazine sulphate and barium dithionate. It is obtained as large crystals. On evaporation over sulphuric acid it decomposes with separation of sulphuric anhydride and is converted into a mixture of hydrazine sulphate and secondary hydrazine dithionate, (N3H4)2.H3S306.a... 

Analysis always necessitates determinations of the sugar (saccharose) and of the soluble salts, since from these is calculated the yield (rendement) on refining. Determinations may also be made of the invert sugar, water, non-sugar and, in some cases, raffinose, total ash and alkalinity sometimes sulphurous anhydride is tested for, but the colour is seldom measured. 

When the wine contains a marked quantity of sulphurous anhydride, this should first be eliminated by boiling the strongly acidified wine (with HC1) for some time in an atmosphere of carbon dioxide. 

Detection of Sulphur Dioxide.—Sulphurous anhydride, which is often added to tanning extracts, either as such or more often as sulphites, to enhance their keeping qualities, may be detected by treating 10 grams of the extract in a beaker with 20 c.c. of hydrochloric acid and 20 c.c. of water, a piece of pure zinc being added and the beaker covered with a clock-glass under which is suspended a strip of lead acetate paper if the extract contains sulphurous anhydride, the paper becomes brown or assumes a blackish tint with metallic reflection. If the paper remains white for 15 minutes, absence of sulphurous acid may be assumed. 

Quantitative analysis of tanning products (raw materials and extracts) requires firstly rational sampling and then suitable preparation of the sample and solution, and includes mainly determinations of the total soluble matters, the tannins and non-tannins, water and insoluble substances.1 Other determinations sometimes made are those of the ash, sugar and sulphurous anhydride, and in industrial practice the specific gravity and colour of the solutions are often measured. 

Sulphurous Anhydride.—The total sulphurous anhydride (free and combined) is determined by distilling a few grams of the extract (weighed exactly), after dilution with water and treatment with a little phosphoric add. The distillate is caught in a solution of iodine in potassium iodide, in which the sulphuric add is subsequently predpitated by barium chloride... 

As regards extracts, their composition varies greatly according both to the methods of preparation and purification and to the degree of concentration. With these the possibility of adulteration, especially with glucose, molasses, cellulose extracts and mineral salts, is to be considered. Addition of sulphurous anhydride or sulphites is allowed, for either clarification or preservation of the extract the proportion of total sulphurous acid may reach and even exceed 2%. 

The difference between these two amounts (as SO,) is diminished by 014% (referred to leather with the normal amount of moisture), this being the mean quantity of SO, formed, during the determination of the total sulphuric acid, by the oxidation of the sulphur in the hide substance. It scarcely needs mention that, when aluminium, chromium and ferric sulphates are present, these lose sulphuric anhydride during the determination of the combined sulphuric acid and are converted into oxides. To obtain exact results in this case, it is necessary to ignite strongly to complete decomposition of these sulphates, to estimate the three oxides in the ash and to subtract from the resultant free sulphuric add also the SO, corresponding with the oxides thus found. 

By this treatment all woollen fibres are coloured a more or less intense yellow. On exposure to the air, however, fibres which have been bleached soon begin to turn paler and after a few minutes (usually not more than 15) become colourless or white again, whereas raw fibres which have not been treated with sulphurous anhydride retain an intense yellow coloration even after an hour. Fibres which have been incompletely bleached (milk white, ivory white) retain the yellow colour of the iodine, although in less intensity, for some minutes, but after an hour they are almost always colourless, or only pale canary-yellow. 

A considerable rise of temperature takes place on mixing sulphuric acid with water it is not improbable that the first anhydride of the true ortho-acid is formed the compound of the formula H2S0,.H20, which may be 0=S=(0H)4, melts at 8°. The point of maximum contraction of a mixture of sulphuric acid and water occurs when the proportion corresponds to H2S04.2H20 this is possibly S(OH)fi, but it does not easily solidify. Water can be withdrawn from sulphuric acid by distilling it with phosphorus pentoxide, when sulphuric anhydride is formed and distils over. 

Sulphates of the alkali- and alkaline-earth metals are stable at all temperatures lower than that of the electric arc but all other sulphates decompose, the primary product being the oxide of the metal and sulphuric anhydride the latter, however, being unstable at a red-heat, decomposes partly into sulphur dioxide and free oxygen. This decomposition is made use of in the preparation of Nordhausen sulphuric acid, a fuming liquid, consisting chiefly of H2S207 it is made by distilling partially dried ferrous sulphate from fireclay retorts 2 Fe S 04 = Fe2 Oa + S 02 + S 03 the... 

Sapozhnikov5s view was partly confirmed by Walden [17], Halban and Eisen-brand found [18] that the absorption spectrum of pure nitric acid in the ultraviolet differed completely from its spectrum when in solution in anhydrous sulphuric acid. The authors explained this observation by assuming the existence of the nitric anhydride or the mixed nitric-sulphuric anhydride. This assumption seemed to be all the more probable as in some earlier papers the idea had already been expressed that N205 might exist in concentrated nitric acid. Thus in 1898... 

Sulphurous Acid is formed when sulphur dioxide dissolves in water. Sulphur dioxide is, therefore, sulphurous anhydride. The simplest equation expressing this fact is —... 

Anhydride, n. An oxide which unites with water to form an acid, e.g. sulphurous anhydride, carbonic anhydride. Often called an acid anhydride. 

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