Refractive Index Nomograph for
iquid Fatty Acids D
ORINSON, McCorkle, and Ralston ( 2 ) presented excellent data covering the variation of refractive index, n& with temperature, t O C., for the normal saturated fatty acids from caproic to stearic, inclusive, in the liquid state. They established the general linearity of n4, with t and showed a break in the curve at 40' C. for the acids from caproic to pelargonic, inclusive. These data enabled the construction of a chart, by line coordinate methods ( I ) , for determining the refractive ,indices of these acids at any temperature in the range of applicability. The use of the chart is illustrated as follows: What is the refractive index of pelargonic acid a t 60' C.? As shown by the broken line, connect 60 on the t-scale with the pelargonic acid point labeled 40 - 80" and produce the line to the n4, axis where the refractive index is read as 1.4171. In a similar manner, using the other pelargonic acid point, the refractive index at 30' C. is found to be 1,4287 although the isopleth for thwe data is not shown. The full-scale ---chart (10 X 17 inches) yields values of n4, which agree with the original data within the probable experimental error.
'
D. %DAVIS
Wyandotte Chemicals Corporation, Wyandotte, Mich.
E"" Furry Acid
o
Sreuric
70-60'c.
0 Marqaric
65-80.
Q Pahitic
o Pentadecanoic
55-e~'
Q
Myristic
0
Tridecanok
50-80'
L -
o
Lauric
45-80.
----
o Hendecanoic Q
._
40-80'
Capric
.-
---
LITERATURE CITED
(1) Davis, D. E?., "Empirical Equations and Nomography", 1st ed., p. 140, New York, McGraw-Hill Book Go., 1943. (2) Dorinson, A.,McCorkle, M. R., and Ralston, A. W., J. Am. Chem. Xoo., 64,2739 (1942).
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I
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