Thiosulphate acid reaction - microscale
Many chemical reactions proceed so fast that it is very difficult to measure them. There are, fortunately, a number of slower reactions that can easily be followed in school science laboratories. The reaction between sodium thiosulphate and acid is one such reaction and is mentioned in almost all textbooks.
However, the reaction produces a toxic product, sulphur dioxide, which has caused many schools to stop doing it. In this reduced-scale method, very good results are obtained using only one fifth of the volumes used in traditional methods. The production of sulphur dioxide is reduced by using a 'stop bath'.
Interestingly, although extensively studied in schools, not a lot is known about this reaction!