Preparation of sodium trithionate trihydrate
62 g of sodium thiosulfate 5-hydrate are dissolved in 50ml of water and cooled to 0-10°C. The solution is stirred mechanically and the temperature range maintained while 52ml of fresh 30% hydrogen peroxide are added by drops from a burette or separatory funnel. Sodium sulfate precipitates during the reaction and is almost completely (about 1-2g remain in solution) removed by cooling the oxidized solution to — 10°C and filtering quickly by suction through a previously cooled fritted glass or Buchner funnel. The hydrated product is obtained by evaporating the filtrate to a sirupy consistency in vacuo and scratching the walls of the vessel. The material is filtered off without washing and the mother liquor may be concentrated further. If the evaporation is carried too far, however, appreciable amounts of sodium sulfate will contaminate the product. The yield depends on the extent of evaporation, but about 70% of the theoretical amount may be expected. Anhydrous sodium trithionate is formed in about 80-85% yield when the sulfate-free oxidized filtrate is run slowly into 150ml of alcohol. The precipitated crystalline salt is washed on the filter with about 50ml of alcohol and dried in air.
Inorganic laboratory preparations, by G. G. Schlessinger, 70-71, 1962
21 g of sodium bisulfite and 0.5g of sodium arsenite are dissolved in a small volume of water and then made up to a volume of 40ml in a 125ml filter flask. 25 g of finely powdered sodium thiosulfate 5-hydrate are dissolved in the solution and the flask is fitted with a stopper and a delivery tube leading almost to the bottom of the vessel. The flask (with stopper and tube) and contents are now weighed to 0.1g on a pan balance. Sulfur dioxide is passed into the liquid to the saturation point and the reaction mixture is allowed to stand for about 15 minutes. The solution now takes up more of the gas and, by repeating this saturating and standing several times during a period of about four hours, a total of 10-11g of sulfur dioxide will have been absorbed. Any crystalline precipitate that forms during the early part of the reaction may be ignored, as it dissolves later on. The reaction mixture is allowed to stand at room temperature overnight and the next day treatment with sulfur dioxide is continued until a total of 13-14g (theory = 12.8g) of the gas has been absorbed. After standing for another 24 hours the reaction has been completed. Sodium trithionate may be isolated by evaporating the liquid (plus any deposited crystals of product) in vacuo, and isolating the salt as described in above. The anhydrous product is formed when the liquid (warmed slightly to 30-35 °C to redissolve any crystals) is poured slowly with good stirring into 75ml of 95% alcohol.
Inorganic laboratory preparations, by G. G. Schlessinger, 71-72, 1962