Calcium sulphite

It is prepared by heating together phosphorus pentachloride and a sulphite, for example calcium sulphite ... 

In determinations of sulphurous acid and sulphites, excess of standard 0.05M iodine is diluted with several volumes of water, acidified with hydrochloric or sulphuric acid, and a known volume of the sulphite or sulphurous acid solution is added slowly and with constant stirring from a burette, with the jet close to the surface of the liquid. The excess of iodine is then titrated with standard 0.1M sodium thiosulphate. Solid soluble sulphites are finely powdered and added directly to the iodine solution. Insoluble sulphites (e.g. calcium sulphite) react very slowly, and must be in a very fine state of division. 

From Salts.—(a) Sulphites, thiosulphates and polythionates readily liberate sulphur dioxide when treated with an acid, or, in the case of the salts of the heavier metals, when merely heated. Calcium sulphite mixed with plaster of Paris and moulded into cubes forms a suitable material for use with sulphuric acid in an automatic gas generator such as Kipp s apparatus.6... 

According to the present theory (e.g. Zherebov [1]) most of the hemicelluloses, pentosans and hexosans are removed during sulphitation, because calcium sulphite is capable of forming addition compounds with pentosans. Complete removal of hemicelluloses is only possible however after lignins have been removed, as lignin seems likely to be chemically combined with hemicellulose and thus with pentosans or hexosans. Only rupture of these bonds and the separation of lignins makes it possible to attack the non-cellulosic polysaccharides (Heuser and Haug [2]). 

Lime water This test is carried out by adding dilute hydrochloric acid to the solid sulphite, and bubbling the evolved sulphur dioxide through lime water (Fig. IV.l) a white precipitate of calcium sulphite CaS03 is formed. 

The dehydration of CaSOj. HjO was studied [16] between 573 and 673 K (an unusually high temperature for this type of reaction) and the value of ii, for the loss of water of crystallization was 173 kJ mol. The rate of the established reaction (but not the rate equation) was very close to that measured under similar conditions for dehydration of Ca(OH)2 (with Ti, = 174 kJ mol ) [80]. It was concluded that both reactions proceeded in a temperature range where proton transfer occurs readily [81]. The bond structure of the water in calcium sulphite hemihydrate may contain features similar to those in Ca(OH)2 at reaction temperatures [80]. 

Sulphite of lime CaS03.2H20 Calcium sulphite. 

Caldum sulfite Calcium sulphite, EINECS 233-596-8 Kataisit,... 

The production of juices for the direct manufacture of white sugar requires a more thorough elimination of non-sucrose compounds. This is achieved in the sulphitation process by the addition of milk of lime and sulphur dioxide and removal of calcium sulphite. 

Sulphur dioxide Sodium sulphite Calcium sulphite... 

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