The reaction produce a yellow precipitate that covers the "PK2" mark under the conical flask. The time taken varies depends on the concentration of sodium thiosulphate solution used.

The rate of reaction is directly related to the concentration of the reactants. The higher the concentration of the reactants, the faster the reaction.

For example, Sulphur, S precipitated faster when more concentrated solution of sodium thiosulphate(VI) reacts with sulphuric acid.

The higher the number of molecules, the greater is the number of collisions in unit time, and hence, the faster the reaction. As the reactants are used up, the concentration drops and the rate of reaction decreases. This also explains the common observation that the rate of reaction reduces with time and eventually tapers off to zero when the limiting reactant is used up completely.

The experiment done on this topic can be reviewed here: Amali Kimia: The Effect Of Concentration On The Rate Of Reaction

REMARKS: The "product" was a bit smelly...