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INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 9,NO. 5
tion of the I. P. T. method in which the test tube employed is a very narrow one and the quantities of sample and aniline are reduced to 1 ml. each. TABLE11. READINQS ON THREESAMPLES Sample 10 Time of Temp. outflow c. Sec. 28.0 36.2 27.9 36.6 27.8 37.1 27.7 37.4 27.5 38.0 27.4 38.7 27.3 39.2 27.2 39.8 27.1 40.5 27.0 41.4 26.95 42.4 26.9 44.0 26.8 44.9 26.7 44.8 26.6 44.0 26.5 43.6 26.4 43.0
FIGURE 3. CURVEFOR SAMPLE 28
not agree, because of varying amounts of each ingredient running through the capillary. Slow cooling of the bath is accomplished by having the immersion heater wired in series with a heavy rheostat. By adding or taking away resistance from the heater, the cooling can be cut down to a very slow rate. A smooth rate of cooling of about l oC. in 5 to 10 minutes was found to be satisfactory. I n case a sample has a solution temperature below room temperature, an immersed copper cooling coil is a convenience for further lowering the bath temperature. Table I compares solution temperatures of different samples by various methods. The narrow-tube method is a modifica-
Sample 25 Time of outflow c. Sec. 68.0 20.1 67.5 20.3 65.7 21.1 64.8 21.8 64.5 22.7 64.0 23.8 63.6 23.4 63.2 23.2 62.4 22.9 62.0 22.8 56.2 24.4 55.7 24.7 54.9 25.5
Temp.
.. .. ..
..
.. .. .. ..
Sample 28 Time of outflow c. Sec. 104.2 37.4 103.8 38.0 103.6 38.2 103.1 39.0 102.8 39.4 102.25 40.2 101.8 41.4 101.6 42.6 101.3 42.3 101.2 41.6 101.0 38.0
Temp.
... ... ...
*..
...
...
....* . .. .. ..
Table I1 and Figures 1, 2, and 3 illustrate the rise of the viscosity to a peak and its subsequent fall, the peak representing the aniline point. Readings on run of sample 25 were continued in order to show the second upward turn of viscosity after the peak in viscosity had been reached.
Summary A new method is described for the determination of aniline point or solution temperature, applicable particularly to darkcolored samples.
Literature Cited (1) Inst. Petroleum Tech., “Standard Methods of Testing Petroleum and Its Products,” 3rd ed., p. 20, 1935. I. P. T. Serial Designations F. 0.23. (2) Tizard, H. T., and Marshall, A. G., J. SOC.Chern. Ind., 40, 20T (1921). (3) Van Wyk, W. R., J . Inst. Petroleum Tech., 22,754 (1936).
RECEIVED February 6, 1937.
Refractive Index of Strontium Nitrate M. L. YAKOWITZ AND P. S. JORGENSEN Food and Drug Administration, U. S. Department of Agriculture, San FranciscQ, Calif.
T
HE use of immersion methods for determining the refractive indices of solids requires a series of immersion liquids whose refractive indices are known with an accuracy of about 0.001. The refractive indices of the immersion liquids may be determined in a refractometer or by use of a series of isotropic crystals whose refractive indices are known. Chamot and Mason (9) list such a series of isotropic crystals to be used in determining the refractive indices of liquids by immersion methods. In this list, the refractive index of strontium”nitrate[Sr(NO&] is given as 1.567. While checking the refractive indices of a set of immersion oils, it was found that the value given by Chamot and Mason is incorrect, The refractive index of strontium nitrate determined by the immersion method, using white light, is 1.586. The sample of strontium nitrate used was analyzed and found to be pure Sr(N0J2 with less than 0.1 per cent water. A check of the literature showed that the refractive index of strontium nitrate is given as 1.5667 by International Critical Tables ( 7 ) , Fry ( 5 ) , and Landolt, Bornstein, and Roth (9). The compilers of these tables apparently took the value of 1.5667 from the standard work of Groth (6),
who depended upon the determinations of Fock (4) and Craw ( 3 ) . The correct value is given by Behr (1) who found strontium nitrate to have a refractive index of 1.5878, using sodium light and the more accurate crystal refractometer. Keenan (8) states that he has depended on Behr’s determination, which appears to be more nearly correct.
Literature Cited (1) Behr, NeuesSahrb. Mineral. Geol., 1, 138 (1903).
(2) Chamot, E. M., and Mason, C. W., “Handbook of Chemical Microscopy,” Vol. I, p. 387, New York, John Wiley & Sons, 1931. (3) Craw, Z.phys. Chem.,19,277(1896). (4) Fock, 2.K r y s t . Mineral. Petrog., 4,585(1880). (5) Fry, W. H., U. S. Dept. Agr., Bull. 1108 (1922). (6) Groth, P., “Chemische Krystallographie,” Vol. 11, p. 104, Leipzig, W. Engelmann, 1908. (7) Intern. Critical Tables, Vol. I, p. 165, General Index No. 2458 (1926). (8) Keenan, G. L., private communication. (9) Landolt, Bornstein, and Roth, “Physikalisch-chemisohe Tabellen,” p. 983,Table 212-D (1912). RBCEIVBDMarch 19, 1987.
