March 1950
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
dellite. The imperfectly crystallized minerals showing a more or less incomplete x-ray pattern which have been generally called 7-manganese dioxide are really impure varieties of ramsdellite or pyrolusite. There is a series of patterns of infinite gradations between ramsdellite and pyrolusite. Ramsdellite and pyrolusite are known in the form of 100% manganese dioxide crystals but ymanganese dioxide and cryptomelane so far have tenaciously retained various impurities. The cryptomelane group comprises a series of alkali compounds between Mn8016 and KJkfns016. The names &manganese dioxide and manganous manganite designate compounds of alkali and manganese oxides in variable proportion and, therefore, are incorrectly chosen. ACKNOWLEDGMENT
The author is indebted to J. A. Tauber for design and construction of the differential thermal analysis apparatus and for his many suggestions, to H. A. Ileiligman and R. J. Otten for their guidance and helpful criticism, to RI. Fleischer who furnished the
527
well-crystallized specimen of ramsdellite, and to E. J. Lavino and Company for permission to publish this paper. LITERATURE CITED
(1) Berkelhamer. L. H.. U.8.Bur. Mines. Tech. Pub. 664 (19.18). (2j Cole, W. F.,'Wadsley, A. D., and Walkley, A., Trans. Eledrochem. SOC.,92,22 pp. (1947) (Preprint). (3) Copland, L. C., Griffith, F. S., and Schertringer,C. B., Ibia., 8 pp. (4) Delano, P. H., paper presented before the government-sponsored Dry Battery Research Committee, Boston, Mass., October 1947. (5) Dubois,P., Ann. chim., 5 , 411-82 (1936). (6) Feitknecht, W., and Marti, W., Helv. Chim. Acta., 28, 129-55 (1945). (7) Fleischer, M., and Richmond, W. E., Econ. Geol., 38, 2GS-86
(1943). (8) Glemser, O., Ber., 72B, 1879-81 (1939). (9) McMurdie, H. F., Trans. Electrochem. Soc., 86, 313-26 (1944). (IO) McMurdie, H. F., and Golovato, E., J . Research iVall. Bur. Standards, 41, 589-600 (1948). RECEIVED May 5, 1948. Presented before the Division of Physical and Inorganic Chemistry at the 113th Meeting of the AMERICANCHEMICAL 50CIETY, Chicago, Ill.
CORRELATING VISCOSITIES Caustic Soda Solutions DONALD F. OTIIMER AND SALVATORE J. SILVISi Polytechnic Institute of Brooklyn, Brooklyn 2, N . .'1 Viscosities of solutions of solids in liquids or of mixtures of liquids have been correlated on a logarithmic plot against vapor pressures or viscosities of a reference substance at the same temperature. In the important case of aqueous solutions of caustic soda, the plot of viscosity against the viscosity of water eliminates the break in the function otherwise experienced at 40" C. A nomograph is presented.
ture. The same characteristics were shown by a plot of viscosities of aqueous sucrose solutions made in this way (6). This break in the line for the viscosities of water conforms to the break for densities ( 4 ) , surface tensions ( 5 ) ,and others which have been indicated previously. The logarithmic plot as presented before ( 3 ) ,in such a way as to give straight lines (Figure l), TEMPERATURE
20
1
LTHOUGH much work has been done on methods of presentation and correlation of data for viscosities of pure liquids, liquid mixtures or solutions have generally been neglected. These data are usually presented as isotherms with viscosity as a curvilinear function of concentration, the independent variable. The slope of such curves makes them undesirable for interpolation and extrapolation with reasonable accuracy. The purpose of this work was to apply a method used for correlating viscosities of pure liquids to those for solutions, particularly those of caustic soda, and from the correlation to construct a nomograph. Viscosities of pure liquids have been shown ( 3 ) to be a straight-line function on logarithmic paper of the vapor pressure of a reference material at the same temperature. The method has now been applied to liquid mixtures and solutions of solids in liquids. In the case of caustic soda solutions, data used are those of Hitchcock and McIIhenny ( I ) throughout the temperature range of their interest-20' to 40" C. Other values in the publication on caustic soda ( 7 ) by the Columbia Chemical Division of Pittsburgh Plate Glass Company, and particularly in a private communication (8) with that company extend the concentration range for solutions up to SO%, in the temperature range 20" to 70" C. Viscosities of water give two straight lines intersecting a t 40 O C. (3) as shown by the lowest line (where the concentration is zero) in Figure 1; the other lines of constant concentration of aqueous solutions of caustic soda also show the break a t the same temperaI Present address, Colgate-Palmolive-Peet Company, Jersey City,
N. J
30
40
50
-"C 60
. ~
VISCOSITY of WATER
Figure 1. Logarithmic Plot of Viscosity of Caustic Soda Solutions against Temperature Scale Based on Vapor Pressures of Water
.c
Figure 2. Logarithmic Plot of Viscosity of Caustic Soda Solutions against Temperature Scale Based on Viscosity of Water
As the viscosity deoreases with increasing temperature, the calibrationa of viscosity are reversed on the horizontal axis to have the temperatures increase from left to right
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INDUSTRIAL AND ENGINEERING CHEMISTRY
IO0 OF
80
"C 100
60
90
40
140460
-: -a IO+ 8.0 6.0
5
o I
>
4.0
40
W
-I -
a
= 80
30
W
cn 0 0
m 2.0
'
,Oi
I .o
o .a 0.6
30
0
0.4 -3 Figure 3. Nomograph Relating Viscosities, Concentrations (Weight Degrees Twaddell), and Temperatures of Caustic Soda Solutions
70,or
Although the experimental data cover the temperature range from 20° t o 70° C.. it is felt that these data may safely be extrapolated to Oo and 100' C., and the nomograph is so prepared. Use of the nomograph depends on a straight line drawn t o cut the three scales on the appropriate values (for example see insert). A solution a t a temperature of 60° C. (point 1 on scale T) and a concentration of 30% NaOH (point 2 o n scale C) are connected on the nomograph by a straight line. The extension of this line intersects scale V a t point 3, giving the viscosity of the solution as 3.25 centipoises.
shows up changes of the general function which would be so small as to be missed, if normal curvilinear plots were used. In the usual plot of viscosity against temperature, it would be impossible to detect visually that the constants in an equation representing the curve were changing slightly-that is, when the rate of change of slope increases or decreases suddenly from the established function. With a straight-line function and plot, this may be detected immediatelv for even a very slight change. Unfortunately, the correlation on isotherms is usually done by smoothing the data through or around this break point rrith the result that a single function, curve, or set of constants in an empirical equation is in error more or less over the entire temperature range involved. Since it has also been shown that a plot of viscosity against the viscosity of a reference material a t the same temperature on logarithmic paper yielded straight lines ( S ) , a plot of viscosities of aqueous solutions using the viscosity of water itself as the reference was made (Figure 2) with the thought that it viould yield straight lines, without a break, throughout the range. That this
Vol. 42, No. 3
was the case is shown in the following consideration. If ml is the slope of a line of constant composition of Figure 1 below 40" C., and m2 is the slope of the same line of constant composition above 40" C , there is a constant ratio between ml and m2, regardless of the concentration, or ml = k m l , and this ratio k is the same as that of the slopes for water. This follows as the ratio k of the slopes of lines in Figure 1 above and below 40 C. is a constant. This is an interesting example of the general premise on which reference plots are based-that is, plotting data for one substance against those for another tends to eliminate the effect of the irregularities of each. In this case, the break points for caustic solutions are balanced exactly by the one for n.ater. Straight lines are obtained as shown in Figure 2 for caustic soda solutions and have also been noted for similar plots of sucrose solutions (6) and by Kobe and McCormack for the waste liquors resulting from pulping operations ( 2 ) . I t is possible to make a nomograph directly from this presentation by simple methods, since the horizontal and vertical scales of Figure 2 are made immediately into two parallel scales of an alignment chart; and concentration is calibrated as a series of points forming a smooth curve between the two. The nomograph of Figure 3 is calibrated for use with either Fahrenheit or centig ade temperatures and for concentrations expressed either as weight per cent caustic soda or density in degrees Twaddell. A straight line betneen the desired temperature on the right scale and the concentration on the center scale gives the viscosity on the left scale. ACKiYOW' LEDGiMENT
Thanks are due Leroy C. Nelson of the Columbia Chemical Division, Pittsburgh Plate Glass Company, and the laboratories of that company for making available their data represented on the nomograph. LITERATURE CITED
(1) Hitchoock, L. B., and McIlhenny, J. S., ISD. ENG.CHEM.,27, 461 (1935). (2) Kobe, K. A., and MoCormack, E. J., Ibid., 41, 2847 (1949). (3) Othmer, D. F., and Conwell, J. hl., IDid., 37, 1112 (1945). (4) Othmer, D. F., Josefowita, S., and Schmutzler, A . E., I b i d . , 40, 883 (1948). ( 5 ) I b i d . , 40, 886 (1948). (6) Othmer, D. F., and Silvis, S. J., Sugar, 43, No. 5 , 32 (1948). (7) Pittsburgh Plate Glass Company, Columbia Chemical Division, "Caustic Soda," 1948. (8) Pittsburgh Plate Glass Company, Columbia Chemical Division, private communication. RECZIYED April 1, 1949.
Previous articles in this series have appeared in
IND. EIG. CHEM.during 1940, 1342-46, 1948, and 1949; Chem. Met. Eng., 1940; Chimie & Industrie, 1918; Euclides (hladrid), 1948; and Sugar, 1948.
