INDUSTRIAL AND ENGINEERING CHEMISTRY
976
curve is in use as a rapid routine analytical measure of the treatment of soybean meals, it was hoped that accurate reflectance measurements would indicate whether the relation between color and denaturation was real or accidental. The spectrophotometric reflectance curves of Figure 2 indicate that the darkening effect apparent to the eye is due to a decreasing reflectance in the blue or short wave length region. The reflectance up t o a wave length of about 500 millimicrons indicates the treatment the sample has received, but beyond that point the inversion of certain of the curves destroys the proper order. Although the trichromic coefficients (Table 111) show remarkable consistency, it was not possible on the basis of the limited data to deduce a definite relation between reflectance and denaturation. The data appeared to indicate that a plot of the violet sensitivity or of the red/green ratio against the denaturation should produce a family of curves with the location of each curve dependent upon the treatment the particular series had received. For closely related conditions these curves would lie close together; therefore, for such treatments an analytical procedure based on a calibration curve for a total reflectance instrument sensitive in the short wave region of the visible spectrum should be reliable as a means of rapidly determining the effect of heat treatment on the meal in terms of nitrogen solubility, denaturation, or related effects. The development of the color change could occur in one or more of several ways: (a) as a result of a change in the protein itself; (b) as a result of a change in a carbohydrate or other fraction intimately associated with the protein and influenced by a change in the protein; or (c) as a result of a change in a carbohydrate or other meal fraction not directly connected to the protein or affected by a change in it. It seems probable that an extension of this work could eliminate some of the possibilities. The indication is that the color
voi. 34, NO.
a
change is a reaction which occurs simultaneously with denaturation, and which is affected by the same conditions of temperature and moisture but is not directly related to the denaturation. The plastic behavior of the heat-treated meal is especially interesting in view of the relatively simple and inexpensive mode of preparation coupled with the insolubility in water and the stability when immersed in water. The insolubility in water is, without doubt, closely related to the fact that water has little or no action as a plasticizing agent for plastic flow, and this is in contrast t o the behavior of the original meal ( 1 ) which is highly soluble and for which water is the best plasticizing agent. The stability of the plastic from the heattreated meal may be contrasted with the plastic from the original meal and protein (4) which disintegrated in less than 24 hours. This work indicates a material with potentialities of development in the low-cost plastic field although its actual worth remains to be tested.
Literature Cited (1) Beckel, A. C., Brother, G. H., and McKinney, L. L., IND.ENG. CHEM.,30,436-40 (1938) (2) Becker, H. C., Milner, R. T., and Nagel, R. H., Cereal Chem., 17, 447 (1940). (3) Boyer, R. A., IND.ENG.CHEW,32, 1549 (1940). (4) Brother, G. H., and McKinney, L. L., Ibid., 30, 1240 (1938). ( 5 ) Chick, H., and Martin, C. J., J. Physibl., 40, 404 (1910); 43, 1 (1911). (6) Cubin, Biochem. J., 23, 25 (1929). (7) Lewis, P. S., Ibid., 20, 965, 978, 984 (1926). (8) Lewis, W. C . M., Chem. Rev., 8 , 81-165 (1931). (9) Mirsky, A. E., and Pauling, Linus. Proc. Nat2. Acad. Sci., 22, 439 (1936). (10) Osborne, T. B., "Vegetable Proteins", 2nd ed. p. 61, New York, Longmans, Green and Co., 1924. (11) Smith, A. K., and Circle, S. J., IND.ENG CHEM., 30.1414 (1938).
Viscosity of Propane, Butane, and Isobutane M. R. LIPHIN, J. A. DAVISON',
AND S. S. KURTZ, JK.
Sun Oil Company, Marcus Hook, Penna.
EW data are available in the literature on the viscosity
F
of the liquid hydrocarbons of less than five carbon atoms. Reviews by Evans (4) and International Critical Tables (8) list only data by Kuenen and Visser on liquid n-butane a t temperatures ranging from approximately -20" t o +100" F. Sage and co-workers (11, 14) determined viscosities of liquid n- and isobutane and liquid propane a t temperatures above 100' F. The authors have determined the kinematic viscosity of liquid propane from -105" to +70° F., of n-butane from -105' to +loo' F. and of isobutane from -105" to +48" F. The viscosities were determined with an accuracy of 1.2 per cent in two types of specially designed capillary-flow viscometers, one for the higher temperature range (Figure I), and the other for the lower (Figure 2 ) . Only a brief description of the two viscometers will be given because an improved viscometer is in the process of development. 1
Present address, University of Pennsylvania, Philadelphia, Penna.
Apparatus and Method The first viscometer (Figure I) was made from the stem of a high-distillation thermometer (30-760' F.), whose ends were ground to a sharp edge bisecting the capillary. The sharp ends do not allow liquid to remain on top of the capillary and, therefore, assure a clean upper meniscus. Without this precaution a chain of bubbles is formed above the top meniscus because liquid is sucked into the capillary. The thermometer stem is held in a glass tube with a cap carrying a Hoke needle valve clamped over its open end. This tube is 28 cm. (11 inches) long, 14 mm. (0.51 inch) 0 . d., and 10 mm. (0.39 inch) i. d., and will withstand an internal pressure of 140 pounds per square inch. The viscometer assembly is filled to mark A , and bulbs a and b fill by gravity. Bfter coming to temperature, the viscometer assembly is inverted and the time of flow measured between marks B and A . Since the measurement is dependent on the ratio of surface tension to density,
August, 1942
977
INDUSTRIAL A N D ENGINEERING CHEMISTRY
% error due t o difference between
x>(z:
0 204 1 surface tension of calibrating = H (Tl- -liquid and unknown where H = head, crn. y1, r2 = radii at liquid levels, om. y1, yz = surface tensions dl, dz = densities
pressure is applied to A . At vapor pressures higher than atmospheric, the bridge and A are ,closed and B is cautiously opened so that the pressure on side A forces the liquid slowly up side B. After each run the liquid level on scale D is read. The viscometer constant is obtained from a calibration curve of liquid level of scale D vs. calibration constant. For the temperature control below 32" F., a large silvered Dewar flask with two visible strips was used. The bath was filled with acetone cooled by solid carbon dioxide, and was provided with an air-driven stirrer. A calibrated singlejunction copper-constantan thermocouple and a Charles Engelhard type P. I. millivoltmeter were used for temperature measurement. The temperature could be controlled within 1" E'. by adding shavings of solid carbon dioxide. When cooled to -7O".F., this bath would not rise in temperature more than 2' F. in 60 minutes.
- - i:) -
FIGURE2.
LOW-PRES-
SURE VISCOMETER
FIGURB1. HIGH-PRESSURE VISCOMETER TEMPERATURE PC.)
the viscometer was calibrated with liquids (benzene, ethyl alcohol, acetone) whose ratios of surface tension to density are fairly close to those of the lower boiling hydrocarbons. Viscosities were run with this instrument in baths thermostated within *0.lo F. This viscometer cannot be conveniently used a t temperatures below 32" F. but is suitable for higher temperatures and high pressures; it is limited only by the strength of the containing tube. (When working with high pressure in this viscometer, a face mask should be used and the arms protected.) The viscometer used a t the lower temperatures and pressures was a modified Fenske type (Figure 2). This viscometer is simple to use and is limited to a gage pressure of about 3 atmospheres because of leakage a t the stopcocks. The viscometer is fdled through valve A . Viscosities are always run with stopcocks A and B closed to the atmosphere, and with the vapor passage open through the bridge between A and B. After the viscometer has been charged and has come to temperature, the calibrated bulb C is filled by one of two procedures. When the vapor pressure is below atmospheric pressure, A and B are opened to the atmosphere with the bridge closed, and
-60
-20
-40
+20
0
m I.C.T. DAm o EXPERIMENTAL- MODIFIED
FENSKE
VISCOMETER
TEMPERATURE (OF,) TEMPERATURE ("C.)
-60
Z W 0
0.5-
z
0.4-
+20
0
-20
-40
>.
c 0.38
o EXPERIMENTAL- MODIFIED
0
v,
>
I
-100
FENSKE VISCOMETER I I I
-80
FIGURE 3.
-60
-40
I
I
1
I
-20 0 20 40 TEMPERATURE (T.)
I
60
I
80
VISCOSITY OF PROPANE, n-BUTANE, AND ISOBUTANE
I
100
INDUSTRIAL AND ENGINEERING CHEMISTRY
978
TABLEI.
--
--Temp.----
c.
\'ISCOSITY
AND
Propaned t/4 (9, Centi6, 9 , 12) stokes
F. - 100 80 - 60 40 - 20 n 26 40 60 80
DENSITY OF PROPANE, n-BUT.kNE, n-Butaned t/4 (8 Centi5,6, 7 , 19) stokes
Ceptipoises
0 487 0.301 -73.3 0.618 0.262 0:432 -62.2 0.606 0 390 0.23l -51.1 0.593 0.580 0 :353 0.205 -40.0 0.567 0.3Z2 0.183 -28.9 0.553 0.163 0.295 -17.8 0.273 0.539 0.14? - 6.7 0.254 0.13; 0.525 4.4 0.237 0.12 0,509 1-16.6 0.492 (0,224) (0.110) +26.7 0.474 (0.210) (0,100) 100 +37.8 0 Values in parentheses obtained by extrapolation.
-
+
The hydrocarbons on which data were obtained mere commercial products of the Ohio Chemical & Manufacturing Company. Purity as determined in our laboratory was 99f per cent; the purities stated in their catalog are propane 99.9 per cent, n-butane 99, isobutane 99.
Results The kinematic viscosities over a temperature range were determined on propane, n-butane, and isobutane (Figure 3). The data form good straight lines when plotted on A. S. T. M. chart D-341-37TI which has been modified by dividing the viscosity scale by 10 and subtracting 100" F. from the temperature scale. Ten centistokes on the original graph equal one centistoke on the revised graph, and 0" F. on the original graph equals -100" F. on the revised graph. No single determination deviates more than 4 per cent from its line. Viscosities determined on propane and n-butane at: the lower temperatures and pressures in the modified Fenske viscometer are in excellent alignment with the viscosities determined in the other instrument at the higher temperatures and pressures. Data from International Critical Tables on n-butane, determined in 1913 by Kuenen and Visser ( 8 ) ,fall on our curve. Sage and Lacey (11, 14) gave a value 2 per cent lower than our best value for n-butane and 12 per cent lower than our best value for both propane and isobutane. J
;* d
b
2.0,
I
w
oOATA OF SHEPARO HENNE 8 MIOGLEY .DATA 4
5
6
7
OF AUTHORS 8
AND
7 -
9 1 0 1 1 1 2
NUMBER OF CARBON ATOMS
FIGURE4. VISCOSITY OF XORMAL PARAFFINS AT 25" C. (77" F.) KO other data are available from the literature. However, a plot (Figure 4) of log kinematic viscosity a t 25" C. vs. number of carbon atoms for the normal liquid hydrocarbons, wing data of Shepard, Henne, and Midgley (15), gives a straight line with which our experimental data for propane and n-butane agree within + 2 and +4 per cent, respectively. Similar type plots by Wiggins (16) of log absolute viscosity :it 20" C. us. number of carbon atoms, and by Kissan and Dunstan (10) of log absolute viscosity vs. molecular volume
Centipoises 0.4S5
0.415 0.36l 0.315 0 . 278 0.248 0 221 0:200 0.181 0.164 0.15O
Vol. 34, No. 8
IsOBUTANEa ------Isobutane---
d t/4 ( I , 2, 9, 11)
0.661 0,649 0.638 0.626 0.614 0.602 0,589
0.577 0.564 0.551 0.537
Centistokes 0 . 85O
0,725 0 . 6ZJ 0.55O 0 . 4S5 0 . 433 0 392 0:356 (0.3Z7) ( 0 .30°) (0.
Centipoises 0 . 562 0.47l 0 . 3Q9 0 . 344 0.29: 0.26 0.231 0.20" (0.184) ( 0 . 165) (0.149)
and log molecular volume, give similar agreement with our data. For engineering purposes, absolute viscosity is often desired rather than kinematic viscosity. Table I gives the kinematic viscosity, density, and absolute viscosity a t 20" F. intervals from -100" t o +100" F. for the three hydrocarbons. The kinematic viscosities were read from Figure 3 and are accurate within *2 per cent. The densities are best values obtained after a search of the literature (1, 2 , 3 , 5, 6, 7 , 9-12) and are dependable within +=0.001. The absolute viscosity is calculated from these data and is also accurate within ~2 per cent.
Acknowledgment The authors wish to acknowledge the assistance of W. T. Harvey and I. W. Mills in connection with a portion of this work.
Literature Cited (1) Burrell, G. A., and Robertson, I. W., J . Bm. Chem. SOC.,37,2188 ( 1915). (2) Coffin, C. C., and Maass, O., Ibid., 50, 1427 (1928). (3) Dana, L. I., Jenkins, A. C., Burdick, J. X., and Timni, H. C., Repig. Eng., 12, 387 (1926). (4) Evans, E. B., J . Inst. Petroleum Tech., 24, 38-53, 321-37 (1938). (5) Grosse, A. von, in Egloff's "Physical Constants of Hydrocarbons", Vol. I, New York, Reinhold Publishing Corp., 1939. (6) Huckel, W., Kraemer, A,, and Thiele, E., J . prakt. Chem., 142, 207 (1935). (7) Kay, W. B., IND.ENQ.CHEM.,32, 358 (1940). (8) Kuenen and Visser, Proc. Roy. Acad. Sci. Amsterdam, 16, 355 (1913); Commun. P h y s . Lab. Univ. Leiden. 138--1(1913); International Critical Tables, Vol. VII, p. 215 (1930). (9) Maass, O., and Wright, C. H., J . A m . Chem. Soc., 43, 1098 (1921). (10) Nissan, A. H., and Dunstan, A. E., J . Inst. Petroleum Tech., 27, 222 (1941). (11) Sage, B. H., and Lacey, W. M., IND. EXG.CHBM.,30, 673-81, 829-34 (1938). (12) Sage, B. H., Schaafsma, J. G., and Lacey, R. N., Ibid., 26, 1218 (1934). (13) Sage, B. H., Webster, D. C., and Lacey, W '. N., Ibid., 29. 1188 (1937). (14) Sage, B. H., Yale, W. D., and Lacey, W. N., Ibid., 31, 223 (1939). (15) Shepard, A. F., Henne, A. I,., and Midgley, T . , J . A m . Chem. SOC.,53, 1948 (1931). (16) Wiggins, W. R., J . Inst. Petroleum Tech., 22, 305 (193W.
Chemistry of Chlorites-Correction An error has been noted on page 788 of the above article which appeared in the July issue. The curve for the formation of sodium chlorate in acid solution in Figure 2 is incorrect. The value as plotted is ten times too large. It should br 0.0001 mole sodium chlorate which accords with the statements in the text JAMES F. WHITS
