The invention relates to compositions which have disinfectant properties, and methods for cleaning and disinfecting using the compositions. Peracetic acid, a disinfectant, is generated by direct reaction of hydrogen peroxide and acetic acid, but a problem is that the solution is thermodynamically unstable. To avoid this problem, peracetic acid may be generated in situ by reacting a suitable peroxide source with an acetyl transfer agent. It would also be desirable to provide the user with an indication of when sufficient peracetic acid has been generated and therefore when the disinfectant solution is ready for use. According to the invention, there is provided a composition which, on dissolution in a solvent, generates a biocidally effective disinfectant solution comprising peracetic acid and hydrogen peroxide. The composition comprises a system to produce a visual indication of the formation of the peracetic acid. More specifically, the invention relates to a powder composition comprising (a) a hydrogen peroxide source (b) an acetyl source and(c) a peracetic acid bleachable dye, wherein, said composition is dissolved in water to form a solution, and colour generated by said peracetic acid bleachable dye is substantially discharged when a biocidally effective concentration of peracetic acid is achieved.
