Journal of Japan Oil Chemists' Society
Online ISSN : 1884-2003
ISSN-L : 0513-398X
Discontinuities in the Coefficients of Thermal Expansion of Long Chain Fatty Acids
Hidesuke TANAKA
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1977 Volume 26 Issue 2 Pages 91-94

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Abstract
The labile d200 of the C form, d020 of the B form, and d100 of the A form for stearic and lauric acids by the changes in temperature were measured from -40°C to near their melting points by the X-ray powder diffraction method. Plots of the side spacing against the temperature showed distinct discontinuities corresponding to the existence of the second order transitions in long chain fatty acids rather than the polymorphic transition. These discontinuities in the coefficients of thermal expansion were observed at the following temperatures : stearic acid-C form, 30°C ; B form, 20°C and lauric acid-C form, 15°C ; A form, 8°C. The coefficients of expansion above the discontinuous points were equal to 1.5 to 2.7 times as great as those below.
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