Preparation of potassium trithionate
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 filtrate is mixed with 35g of potassium acetate, stirred until the latter has dissolved, and kept in ice for about one hour until crystallization is complete. The product is filtered off, washed twice with 30ml portions of 95% alcohol, and dried in air. Yield 80-85% of theory.
Inorganic laboratory preparations, by G. G. Schlessinger, 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. 25g of potassium acetate in the reaction mixture and cooling it in ice. Isolation and yield are the same as described above.
Inorganic laboratory preparations, by G. G. Schlessinger, 72, 1962