Question

Why is Sodium thiosulphate and sulfuric acid used in the experiment of scattering of light in colloidal solution ?

Answer 1

In this experiment, colloidal sulfur is generated by the reaction of sodium thiosulfate and sulphuric acid in a two- step process involving first the formation of thiosulfuric acid followed by its decomposition to sulfurous acid and colloidal sulfur .

Colloidal suspensions scatter white light strongly. Shorter wavelengths are scattered more while longer wavelengths (reds and oranges) are transmitted. Scattering is when a molecule absorbs a photon of light, exciting an electron into a higher energy state. When the electron returns to a lower energy state, the molecule emits a photon in a random direction. This randomness produces the scattering known as the Tyndall effect. As the sulfur precipitates the higher energy light from the projector will be scattered, making the solution look blue