May 15, 1934
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
very easy to clean. I t s accuracy as well as the ease and time required for its manipulation have been highly satisfactory. It has been developed to measure the degree of thickness or thinness of dilute solutions of starch in terms having practical utility and not to determine whether the consistency is truly viscous or whether a set of readings follows some mathematical equation. A good viscometer for practical purposes should indicate only differences which are apparent to the skilled practical man.
METHODOF TESTING.Place 3000 cc. of distilled water at about 75" F. (23.89' C.) in the boiling can and stir in the proper amount of starch. Open valve pipes P and PP to drain condensation and heat them; then close the valves, attach the boiling can t o hook H , and open wide the valves or pipes P and PP. After 20 seconds the mixture will gelat'inize and the flow of steam through P must be reduced immediately, so that the force of the steam will not blow the paste out of the can. Continue to manipulat,e the valve for P, so that the temperature is brought steadily up to 190' F. (87.78" C.) in exactly 1.5 minutes. Thereupon, immediately close the valve for P but allow the constant flow of st,eam through PP and the constant agitation caused thereby to continue as long as desired. The temperature of the solution rises rapidly to the boiling point, where it remains. It has been the custom of this laboratory when testing cassava flour for ordinary control purposes to use 200 grams and to remove the can for testing 3 minutes after opening valve pipe P. At this point the viscometer cup with a 0.22-inch (0.556-cm.) orifice is placed in the so1ut)ion; the time required for the cup to submerge is the viscosity measure. Exactly 2 minutes after the removal of the can it is replaced and boiling is continued until the total time elapsed has reached 17 minutes, whereupon the can is again removed and tested with a 0.125-inch (0.317-cm.) orifice in the viscometer. The first reading with the 0.22-inch (0.556-cm.) orifice can be converted into equivalent readings for
187
the 0.125-inch (0.317-cm.) orifice by means of a predetermined set of values, and these viscosity readings in seconds can be converted into centipoises after standardizing the 0.125-inch (0.317om.) orifice against solutions having a known viscosity in centipoises. For ordinary purposes readings in seconds are preferred. STANDARDIZING APPARATUS. To standardize the cooking apparatus, open wide the valve for pipe PP and allow steam to flow until the pipe is hot; then put 4000 cc. of water a t a temperature of about 70' F. (21.1" C.) into the cooking can and place it on the hook. The time required to raise the temperature from 75" to 100' F. (23.89' to 37.78" C.) should be approximately 3 minutes and 13 seconds. The viscometer cup is standardized by measuring the time required for it to sink in water at ap roximately 75" F. (23.89' C.). The cup with an 0.125-inch 6.317-cm.) orifice sinks in 19.3 seconds and with the 0.22-inch (0.556-cm.) orifice the time is 7.1 seconds. With this apparatus and method of cooking the condensation should be very close to 350 cc. after 3 minutes of cooking and 30 cc. for every additional 10 minutes when a test is made using 3000 cc. of water and 200 grams of starch. For ordinary testing the condensation after the first 3 minutes is not an important factor.
LITERATURE CITED (1) Caesar, G. v., IND.ENG.CHEM.,24, 1432 (1932). (2) Grimshaw, A. H., Teztile World, 74, 61 (1928). (3) Harvey, E. H., Amer. J . Pham., 96, 816 (1924). (4) Mangels, C. E., and Bailey, C. H., IND.E m . CHEX.,25, 456 (1933). (5) Ripperton, J. C., Hawaii Agr. Expt. Sta., Bull. 63 (1931). (6) Thurber, F. H., IND. ENQ.CHEX,25, 565 (1933). (7) Wiegel, E., Kolloid-Z., 62, 310 (1933). (8) Wolff, O., Chem.-Ztg., 51, 1001 (1927). R ~ C E I V ENovember D 7. 1933.
Determination of Dielectric Constants by Means of Radio M. M. OTTOAND H. H. WENZKE,University of Notre Dame, Notre Dame, Ind.
I
N CONNECTION with research work, a method of deter-
mining dielectric constants accurately with a n inexpensive apparatus was desired. The heterodyne beat method was the most convenient one to use, but a source of constant radio frequency was needed to obtain good results. Broadcasting stations shou'd serve for this purpose, as they are required by federal regulations to keep within twelve cycles of their assigned carrier frequency to guard against interference with stations operating in adjacent channels. If the frequency of the carrier was varied by the audio frequency superimposed upon it, a composite of which is transmitted by the sending station, the radio could not be used as a source of constant oscillations. There is, however, no shift in carrier frequency but audio modulation adds what are called side bands on each side of the carrier wave and removed from i t a number of cycles equal to the modulating frequency. Another oscillator coupled to a radio receiving the modulated carrier wave of the broadcasting station can be made to form an audible beat note which has a frequency equal to the difference in cycles between carrier and the oscillator. This beat note, together with a jumble of distorted music, is given out by the radio. B y slowly tuning the variable oscillator the beat note can be made to become lower in frequency and the music less distorted until, a t what is called zero beat, the music is undistorted and can be heard exactly as if the second oscillator were not in operation. Having a method of setting a variable oscillator to constant frequency, the usual procedure of the heterodyne beat method
for determining dielectric constants was then followed. As is known, the dielectric constant may be taken as the ratio of the capacity of a given condenser filled with the medium to be measured, divided by the capacity of the same condenser evacuated or, for most practical purposes, filled with air. By connecting the measuring condenser in parallel with a condenser previously calibrated, the capacities are added, and if the standard condenser had been set for zero beat with the broadcast station it must be detuned a n amount equal to the capacity of the measuring cell again to have zero beat. Repetition of the process with air and a n unknown substance in the measuring cell makes it possible to calculate the dielectric constant.
APPARATUB Figure 1 is a diagram of a n ordinary variable oscillator. The measuring cell is similar to that used by Smyth and Morgan ( 8 ) , except that the plates are insulated by beads of glass fused to stiff platinum wires which are welded to the cylindrical plates ( 5 ) . The standard capacity is a General Radio Type 222-L condenser. The condenser system was constructed outside of the oscillator proper, and joined to it by means of the binding posts, P , P'. A Stewart-Warner Model 102-A superheterodyne radio was used to obtain the radio frequency from the broadcasting station. The coupling between the radio set and the variable oscillator was adjusted until the error involved in detecting
ANALYTICAL EDITION
188
zero beat was less than that in reading the scale on the standard condenser. I n order to correct for parasitic capacity, the cell was calibrated by filling it with pure, dried benzene, as is done in the ordinary procedure.
Vol. 6 , No. 3
TABLE11. DATAFOR DETERMINATION OF DIPOLEMOMENTS OF BROMOBENZENE, p-NITROTOLUENE, AND ETHYLBROMIDEIN BENZENE AT 25" C. d
OS
a
Pa
pi2
BROMOBENZENE~
6 d VOLTS
0,02104 0.03134 0.03668 0.05633 0.07708
0.8860 0.8936 0.8974 0.9130 0.9279
0.007925 0.01086 0.02064 0.02094 0.02769 0.03984 0.04877
0.8736 0.8747 0.8783 0.8785 0.8809 0.8855 0.8887
2.347 2.385 2.401 2.469 2.547
27.88 28.46 28.72 29.85 30.85
83.62 83.48 83.16 82.88 80.74
p-NITROTOLUENE b
RADIO
2.495 2.563 2.841 2.845 3.024 3.345 3.583
29.89 30.82 34.32 34.38 36.44 39.84 42.13
432.1 407.4 396.9 394.2 379.2 356.9 343.4
ETHYL BROXIDE?
_L -
AERIAL
0.01084 0.8759 2.324 27.40 0.02984 0.8848 2.413 28.58 0.03604 0.8878 2.441 28.93 0.04497 0.8920 2.482 29.45 0.05804 0.8983 2.544 30.20 a P = 83.9. P E = 33.92. p = 1.55 X 10-18. b P z = 448;' PE = 37 9 ; = 4.44 X 10-18. OPca 94.2; PE 3 18.5: P A = 11; p =s 1.77 x
'lsOOU.ILf.r PRECISION CONDENSER 0002511 f
-
-3
3 VOLT5
FIGURE1. DIAGRAM OF VARIABLEOSCILLATOR Station WGN, Chicago, operating on 720 kilocycles, was used as a source of constant frequency. Their schedule is continuous throughout the day, and the signal in this locality is of sufficient intensity for the work. Other stations may be used, and for purposes of comparison, WBBM, on 770 kilocycles, and WMAQ, on 670 kilocycles, were also used, with no variation in results. With wave lengths near the long wave limit of the broadcast band, the point of zero beat was not sharp, while with shorter wave lengths than that of WBBM, the condenser had too large capacity for the coil used.
The electronic polarization of bromobenzene was obtained from the refractive index for the sodium D line, and the density of the pure liquid. That of p-nitrotoluene was obtained from the same measurements on solutions in benzene, and for ethyl bromide the electronic polarization was taken from the literature. Atomic polarization was neglected in the case of bromobenzene and p-nitrotoluene, but the value for ethyl bromide was taken from Smyth and Morgan (8). The X lo-'* for bromobenzene, 4.44 X values obtained-1.55 10-l8 for p-nitrotoluene, and 1.77 X 10-l8 for ethyl bromidecompare favorably with the values in the literature, as listed in Table 111. TABLE111. ELECTRIC MOMENT VALUES MOMPNTX 1018 BROMOBENZENn
Bergmann (1) Williams (18) Mdller and Sack (6) Das (8) K. Hojendahl (9) Tiganik (11)
MEASUREMENTS OF DIELECTRIC CONSTANTS I n order to test the accuracy of the method, dielectric constants of some known substances were determined. The results of these measurements together with those obtained by other workers are listed in Table I. The agreement is good.
.
TABLEI. DIELECTRICCONSTANTS OF XYLENE, CARBON AND ETHYL ACETATEIN BENZENE TETRACHLORIDE, m-XYLENE e
€
1, o c .
Otto and Wenske
Pyle (7)
36 31 28 26 20
2.349 2.354 2.360 2.363 2.369
2.353 2.359 2.365 2.370 2.374
Smyth and Walls (9)
C¶
€
CP
0.04020 0.05656 0.1188 0.1420
2,435 2.505 2.754 2.849
0.0310 0.0475 0.0614 0.1060 0.1575
....
...
€
2,410 2.477 2.532 2.708 2.912
CARBON TETRACHLORIDE
t.
O C .
20 30 40 50
1.49 1.50 1.52 1.53 1.56 1.53
1)-NITROTOLUINE
Tiganik (11) K. Hojendahl (9) Williams (12)
4.44 4.31 4.50
ETHYL BROMIDE
Smyth and Morgan (8) Mahanti (4)
1.86 1.79
The fact that the values obtained by the use of the radio are within the experimental deviations of other investigators shows clearly that this method is useful and accurate for measuring dipole moments.
LITERATURB CITED
ETHYL ACPTATE I N BENZENE AT 26' C.
Otto and Wenzke
93.1 90.2 89.1 88.2 86.3
€
€
Otto and Wenske
Stranrtthan ( 1 0 )
2.219 2.196 2.182 2.150
2.221 2.200 2.180 2.159
Dielectric constant data on organic compounds are obtained primarily for the purpose of calculating their electric moments. As a further check on this method dipole moments of a number of compounds were determined, The data on this work are given in Table 11.
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
Bergmann, Engel, and Sandor, 2.phgsik. Chem., B10,106 (1930). Das, I n d i a n J. Physics, 5, 441 (1930). Hojendahl, Physik. Z., 30, 391 (1929). Mahanti, Ibid., 31, 546 (1930). Morgan and Lowry, J. Phys. Chem., 34, 2385 (1930). Milller and Sack, Physik. Z., 31, 815 (1930). Pyle, Phys. Rev., 38, 1065 (1931). Smyth and Morgan, J. Am. Chem. SOC.,50, 1547 (1928). Smyth and Walls, Ibid., 53, 527 (1931). Stranathan, Phys. Rev., 31, 653 (1928). Tiganik, 2. physik. Chem., B13, 425 (1931). Williams and Sohwingel, J. Am. Chem. Soc., 50,362 (1928).
RECEIVED November 16, 1933.
JAPANESE DYE PRODUCTION AND FOREIGN TRADE,1933. It is conservatively estimated that the production of synthetic dyestuffs in Japan during 1933 increased by approximately 40 per cent in volume over the output during 1932. The increase in production of cotton textiles and rayon during 1933 probably increased the demand for dyestuffs by at least one-third.
