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Dilatometric investigations of fats. VII. Melting dilation and polymorphism of an alpha and beta tung oil
Author(s) -
Singleton W. S.,
O'Connor Robert T.,
Murray Mildred,
Pack F. C.
Publication year - 1952
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02632626
Subject(s) - melting point , isomerization , chemistry , polymorphism (computer science) , beta (programming language) , analytical chemistry (journal) , crystallography , thermodynamics , mineralogy , chromatography , organic chemistry , physics , biochemistry , computer science , genotype , gene , programming language , catalysis
Summary Three polymorphic forms of beta tung oil have been recognized and differentiated on the bases of their melting points and x‐ray diffraction spacings. These modifications, which melt at 52.8°, 44.4°, and 28.0°C., have been designated as Forms I, II, and III, respectively. Polymorphism was not observed in alpha tung oil. The expansibilities of alpha tung oil and the three original polymorphic modifications of beta tung oil have been determined in both the solid and liquid states, and the melting dilation of each substance was calculated. The absolute densities of the alpha and beta oils were determined, and the absolute specific volumes over the ranges of melting of all these substances were calculated and reduced to graphic form. Forms II and III of the beta oil irreversibly transformed to Form I with contraction in volume during dilatometric examination. The contents of solid and liquid phases of alpha and beta tung oils were calculated over the ranges of melting of these oils. The amount of glycerides in the liquid state was found to increase substantially during the final 10 degrees of the melting range. The isomerization of alpha to beta tung oil under ordinary laboratory illumination was found to be accompanied by a decrease in volume of about 4% and an increase in density. Isomerization in the absence of light reached approximate equilibrium with a decrease in volume of only about 60% of that occurring in the presence of light.