The invention relates to a process for preparing potassium thiosulfate, potassium sulfite or potassium bisulfite comprising the following steps: Step (1a): providing a potassium hydroxide or potassium carbonate solution for neutralizing acid forming components such as dissolving SO2 or H2S; Step (1b): providing an SO2 contacting solution, containing at least some potassium sulfite or potassium bisulfite or potassium thiosulfate; Step (2): providing SO2 gas; Step (3): reacting these to absorb the SO2 gas and to form an intermediate reaction mixture comprising potassium sulfite, or potassium bisulfite or a mixture thereof, and optionally recovering the potassium sulfite, or potassium bisulfite or a mixture thereof, and/or optionally using steps 4 and 5; Step (4): adding sulfur or sulfide containing compound containing sulfur having the oxidation state of 0, −2 or of between 0 and −2 to the reaction mixture and optionally potassium hydroxide or potassium carbonate, and reacting the mixture under suitable conditions to form potassium thiosulfate; and Step (5): recovering the potassium thiosulfate, and optionally concentrating the potassium thiosulfate.