What is the reaction between sodium thiosulphate and FeCl3?

The reaction between sodium thiOSulfate (Na2S2O3) and FeCl3 forms a complex of iron (III) thiOSulfate, Fe(S2O3)3. This complex has a yellow color due to the presence of iron (III) ions. The reaction is often used in analytical chemistry for the titration of thiOSulfate ions.