Solution solute in a solution is the mass of that solute expressed as a percentage of the mass of the whole solution. "Homogeneous" means that the components of the mixture form a single phase. "Heterogeneous" means that the components of the mixture are of different phase. The properties of the mixture (such as concentration, temperature, and density) can be uniformly distributed through the volume but only in absence of diffusion phenomena or after their completion. Usually, the substance present in the greatest amount is considered the solvent. Solvents can be gases, liquids or solids. One or more components present in the
Phase-type distribution (the non-homogeneous case). The mixture of two Erlang distribution with parameter "E"(3,β), "E"(3,β) and (α,α) (such that α + α = 1 and for each "i", α ≥ 0) can be represented as a phase type distribution with and The Coxian distribution is a generalisation of the hypoexponential distribution. Instead of only being able to enter the absorbing state from state "k" it can be reached from any phase. The phase-type representation is given by, and where 0 < "p"...,"p" ≤ 1. In the case where all "p" = 1 we have the hypoexponential distribution. The Coxian distribution is extremely