If the particles are in solution and known to have uniform size dispersity, then a typical strategy is to measure different concentrations of particles in the solution. From the SAXS patterns obtained one can extrapolate to the intensity pattern one would get for a single particle. This is a necessary procedure that eliminates the "concentration effect", which is a small shoulder that appears in the intensity patterns due to the proximity of neighbouring particles. The average distance between particles is then roughly the distance 2π/"q*", where "q*" is the position of the shoulder on the scattering vector range "q". The shoulder thus comes from the structure of the solution and this contribution is called "the structure factor". One can write for the small-angle X-ray scattering intensity: