Evidence is presented in support of the following theory: Petroleum waxes consist of mixtures of hydrocarbons belonging to various homologous series. The members of each series crystallize similarly, as either plates, mal crystals, or needles. If but one type (plate, mal, or needle) is present, the crystal form remains the same regardless of such factors as amount or kind of solvent. If the types are
Examination of the physical properties and crystal forms of twenty highly purified paraffin wax fractions from a midcontinent petroleum indicate that petroleum wax consists of several hydrocarbon series which are homologous at least with respect to physical properties and crystal form.Three broad types of crystal form may be distinguishednamely, plate, mal-crystalline, and needle; the plate type exhibiting, for a given boiling point, the highest melting point, and the needle the lowest. The crystal form is an inherent property of the compound, and is substantially unaltered, except in detail, by factors such as viscosity of the solvent.Both needle and mal-crystalline waxes have marked powers, under the proper conditions, of impressing their form upon plate waxes, and indications are that the malcrystalline type is more powerful in this respect than the needle. These findings reconcile many apparently contradictory observations which appear in the literature, and throw considerable light upon certain wax-refining processes.
THE many variations in the crystalline behavior of the solid constituents of petroleum have given rise to three important theories as to the composition of these waxes:(1) the proto-pyro-paraffin theory of Zaloziecki (.9), which postulates the existence in petroleum of an amorphous wax (probably branch-chain) which upon distillation cracks to the crystalline (straight-chain) variety; (2) the theory advanced by Gurwitsch (/,), which attributes differences in crystal behavior to the properties of the crystallizing medium; and (3) the "soft wax" postulate of Buchler and Graves (1). These writers attributed all crystalline peculiarities to the
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