A suspension is a mixture containing solid particles that can be separated by filtration. Charles E. Ophardt of Elmhurst College explains that a mixture is a combination of two or more substances that are not chemically united and do not exist in fixed proportions to each other.
In contrast to mixtures, pure compounds have a constant composition with fixed ratios of elements. A mixture can be physically separated into pure compounds or elements. Mixtures can be described as either homogeneous or heterogeneous. Homogeneous mixtures have a uniform appearance and composition throughout, while heterogeneous mixtures consist of visibly different substances or phases. A suspension is a type of heterogeneous mixture containing large particles that can settle out on standing or by filtration.