Calcium dithionate

Calcium dithionate, 2 168 Calcium fluoride, as fluorinating agent, 4 137... 

At 30 C, the solubility of calcium dithionate in water exceeds that of calcium sulfate by a factor of 105. According to the principle of Le Chatelier, under a high sulfur dioxide pressure the equilibrium of the given reaction lies on the right-hand side, while at a low pressure of sulfur dioxide essentially only calcium sulfate exists. This implies that when the digesters are depressurized, the high solubility of calcium sulfate is terminated, thus leading to calcium sulfate precipitation. 

See also Magnesium-rare earth nitrates, S3mthesis 15 Calcium dithionate, synthesis 50A... 

The calcium dithionate is recovered by concentrating the solution on a steam bath and cooling. Successive crops of crystals are obtained by fnrther concentration and cooling. When the volume of mother liquor has been reduced to 50 ml., the remaining calcium salt is thrown down by the addition of 75 ml. of ethyl alcohol. The crystal crops are... 

In a preparation starting with 80 g. of Java pyrolusite, 194 g. of calcium dithionate, CaS206-4H20, was obtained. Yield 86 per cent. 

The procedure used in the preparation of calcium dithionate is followed except that barium hydroxide is employed instead of calcium hydroxide. For the amounts specified for calcium dithionate, the initial quantity of barium hydroxide, Ba(OH)2 8H20, should be about 160 g. Because of the greater solubility of barium hydroxide, greater care must be exercised in arriving at the end point (strong alkalinity to litmus paper). 

The crude dithionate solution is prepared in accordance with the instructions given for calcium dithionate. This solution is brought to a temperature of 35 to 40°. With continuous agitation, barium carbonate powder is added a little at a time until ftui,her addition does not cause immediate increase in carbon dioxide evolution. Agita-... 

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