The esters methyl stearate, methyl oleate, methyl linoleate and methyl linolenate are C18 compounds and have respectively no double bonds and one, two and three double bonds”. They occur in biodiesels and are used as model compounds in studying the properties of biodiesels. We therefore expect intuitively that their freezing points would give an indication of the range of cloud points of biodiesels.
Accordingly the freezing points of three of these compounds are given in the table below. A value for methyl linolenate has evaded the author; it is reported as ‘not available’ on safety data sheets and the like. The value for methyl palmitate, which is C16, is in the final row of the table.
For a single compound the cloud and pour points must, by the phase rule, be the same. Manufacturers’ information for ‘methyl oleate’ sometimes gives them as being spaced by 10°C or more. Such a figure is valid only for a product containing methyl oleate at a particular percentage composition and not for the pure compound.