Water is the major solvent in many preparations and, especially in combination with surfactants, is capable of bringing into solution a large number of other substances but it has its limitations and when these are reached the range of organic solvents must be considered. By such means the scope of surfactant formulations is opened up even further.

Because of the large number of organic solvents only the common ones will be considered here. Today's range of solvents available for formulation work is represented in the main by ones that are obtained directly from petroleum or synthesized from petroleum feedstocks. There are also some solvents made from plant materials and, although the proportion of these is relatively small compared with the petroleum-derived solvents it is growing as a result of our desire to become less reliant upon petroleum.

Solvents from plant sources compare well with the petroleum-based ones but there are some noticeable absences, the main ones being the halogenated hydrocarbons, particularly the chlorinated ones. These chlorohydrocarbons are not found in nature to any significant extent. In fact when they do get into natural systems they can wreak havoc but they are excellent solvents and some industrial applications are going to be hard pressed as these solvents are forced off the scene due to environmental concerns.

Many plant-derived solvents cost more than their man-made counterparts and supply of them often fluctuates as they are prone to the uncertainties that are forever present in the business of growing plants. Despite some...