Sodium thiosulphate stop bath

Discussion in 'Supporting Chemistry' started by Debbie and Dawn, May 10, 2018.

  1. Hello
    does anyone know the ratio of 1M sodium carbonate to 20g/litre sodium thiosulphate to neutralise the reaction
  2. Are you using it as a stop bath? if so 25cm3 of sodium carbonate @ 1M will neutralise 50 cm3 of thiosulphate @0.1M
  3. thank you Ann - that is the answer I was looking for.
    Ann Chinnery likes this.
  4. Can I ask what you do with the stop bath solution once it has been used? There is obviously an amount of solid sulphur precipitate at the bottom. I don't seem to be able to find any information on CLEAPPS regarding how to dispose of the stop bath solution after use.
  5. I sieve out any residue with large filter paper-dispose in normal waste and then pour the rest down a foul water drain with plenty of water. ie toilet and flush. :)
  6. We check it is a fairly neutral pH then wash it down the sink with lots of cold water