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Thermal properties of fats and oils. VIII. Specific heats, heats of fusion, and entropy of alpha and beta tung oils
Author(s) -
Ward T. L.,
Singleton W. S.,
Planck R. W.
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/bf02643536
Subject(s) - melting point , enthalpy of fusion , entropy of fusion , thermodynamics , heat capacity , fusion , beta (programming language) , chemistry , materials science , physics , organic chemistry , computer science , programming language , linguistics , philosophy
Summary Beta tung oil belongs to that group of substances which are capable of existing in more than one crystalline form, each of which has a distinet melting point. Three different melting points of the beta tung oil were observed, each dependent upon the rate of cooling. Forms I, II, and III have been used to distinguish beta tung oil melting at 52.8°, 44°, and 28° C., respectively. Equations were developed to express in cals./g./°C. the specific heats of the stable forms of tung oil. Alpha tung oil Solid state (−184° to −43°C.) C p =0.404+0.001 t Liquid state (9° to 80°C.) C p =0.463+0.0011 t Beta tung oil Solid state (−178° to 27°C.) C p =0.390+0.0013 t Liquid state (67° to 87° C.) C p =0.489+0.00016 t The specific heat of beta tung oil was found to be higher when the sample was rapidly cooled than when it was slowly cooled or tempered. The heat of fusion of the beta form of tung oil was caleulated to be 16.12 cals./g., and for the alpha form to be 21.02 cals./g. Entropies at 298.16°K. were 231.04 and 252.15 entropy units for the two forms of these oils, respectively. The liquid glycerides present at any temperature in the melting range were estimated from the data for the heat contents of the oils. The rate of liquidphase formation at constant heat input of both alpha and beta tung oils, unlike that of cottonseed and peanut oils, increased sharply during the final 10° of the interval owing to the greater homogeneity of the glycerides of the former.