Properties of Concentrated Solutions of Sodium Carbonate L. D. ROBERTS
AND
GEORGE B. MANGOLD, JR.
University of Southern California, Los Angeles, Calif.
calibrated a t different temperatures in distilled water. These corrections are necessary because the glass as well as the water expands as the temperature is increased. Viscosity measurements were made with an Ostwald viscometer. The following is an example of a trial with a 2 normal solution a t 50" C.: Time of efflux of water, sec. 52.50 Time of efflux of solution, sec. 85.07 Density of water, gram/cc. 0.9881 Density of solution, gram/cc. 1.084 Viscosity coefficient of water, poise 0.00549 Viscosity coefficient of solution, 7 , poise, 0.00549 X 85.07 X 1.084 = 0.00976 0.9881 X 52.50
The usual Wheatstone bridge method was used to measure the electrical conductance. The cell was constructed according to Washburn (Figure 1). Figure 2 shows the apparatus used for measuring the electromotive force.
FIGURE 1. APPARATUSFOR ELECTRICAL CONDUCTIVITY MEASUREMEKTS A . Dry cells B. Microphone hummer
C. Washburn conductivity cell (type B) Constant-temperature water bath E. Kohlrausch slide wire (1000 ohms) D.
F . Single-contact key G . Four-dial resistance box (9999 ohms) H . Telephone receiver ~
OR theoretical reasons dilute solutions have been thoroughly studied. I n technical and engineering work more knowledge of the properties of concentrated solutions should be obtained. On account of the industrial importance of sodium carbonate, concentrated solutions of this salt have been investigated. Six standard solutions of sodium carbonate were prepared with normalities of 1.000, 2.000, 3.000, 4.000, 5.000, and 6.000, respectively. The purity of a high-grade anhydrous salt (Na2C03)was tested before use. The densities were determined with the pycnometer and with the hydrometer. The pycnometer was not used a t high temperatures. The hydrometer jar was maintained a t a given temperature in a water bath. The hydrometer was
F
TABLE I.
SPECIFIC
Water Cor. sp. gr. 0.99768 0.99224 0,58807 0.98324 0.97781 0.97489 0.97183 0,96865
7 -
Temp., C. 22.5 40.0 50.0 60.0
70.0 75.0
80.0 85.0
Obsvd. sp. gr. 0.99S5 0.995 0.991 0,987 0,984 0.582 0.979 0.577
GRAVITY OF
-0.006
-0.007 -0.007 -0.008
sp. gr. 1.0476 1.046 1.041 1.036 1.032 1,030 1.027 1,025
98.0 0.560C ..... .... .... * Anhvdrous sodium carbonate b D e t e k i n e d with a standard pycnometer. C Estimated b y extrapolation.
A. B.
Dry cells Saturated potassium chloride Hydrogen electrode D . Calomel electrode E . Sodium carbonate solution F . Hydrogen intake G . Constant-temperature water bath H . Standard cell I . Galvanometer J . Two-way switch K. Type K potentiometer C.
WATER AND SODIUM CARBONATE" SOLUTIONS BY
. Obsvd. 1.000 N NazCOs CorrecCor.
tion 0,000 -0.003 -0 003 -0.004
FIGURE 2. APPARATUSFOR ELECTROMOTIVE FORCE MEASUREMENTS
sp. gr. 1.047 1.043 1.038 1.032 1.026 1.023 1.020 1.017 1.O0Qc
2.000
N NazC03
Obsvd. sp. gr. 1.095b 1.093 1.087 1.081 1.078 1.076 1.072 1.070
. .. .
Cor. sp. gr. 1,095 1.090 1.084 1.077 1.072 1.068
1.065 1.062 l.064c
3.000 N NazCO8 Obsvd. Cor. sp. gr. sp. gr. 1.141b 1.141 1,137 1,134 1 , 1 3 1 1.128 1.122 1.126 1.122 1.116 1.112 1.119 1,109 1.116 1 , 1 1 3 1.105
1293
. .. .
1.05Sc
4.000 N Obsvd. sp. gr. 1,185b 1.180 1.173 1,168 1,164 1.161 1.159 1.156
,., .
HYDROMETER MEASUREMENTS NazCOs Cor. sp. gr. 1.185 1.177 1.170 I . 164 1.158 1,154 1.152
1.148 1.140c
5.000 N NazC03 6.000 N NazCOa Obsvd. Cor. Obsvd. Cor. sp. gr. sp. gr. sp. gr. sp. gr. 1.2256 1 . 2 2 5 1.2626 1 . 2 6 2 1.217 1.220 1.267 1,254 1 , 2 1 4 1.211 1.262 1.249 1.247 1.243 1,205 1.209 1,241 1,235 1.198 1.204 1,201 1.231 1,154 1.238 1.197 1 235 1.228 1.190 1 . 145 1.232 1.224 1.187 1.177c . 1.2140
....
... ~~
INDUSTRIAL AND ENGINEERING CHEMISTRY
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VOL. 31, NO. 10
AND COEFFICIENT OF VISCOSITYOF WATERAND SODIUM CARBONATE^ SOLUTIONS TABLE 11. TIMESOF EFFLUX
-WaterTime of Coeff. of Temp. efflux viscosity) a. C. Sec. Poise
22.5 50.0 75.0 98.0 4
101.20 52.50 42.20 34.40
1.000 N NazCOa Time of Coeff.. of efflux viscosity
2.000 N NaaCOa Time of Coeff. of efflux viscosity
Sec. 122.00 68.80 49.50 39.33
Sec. 151.94 85.07 59.20 46.40
0,00949 0,00549 0.00380 0.00289
Anhydrous sodium carbonate.
Poise 0,01201 0,00756 0,00468 0.00347
3.000 N NazCOa Time of Coeff. of efflux viscosity
4.000 N NazCOa Time of Coeff. of efflux viscosity
5.000 N NazCOs Time of Coeff. of efflux viscosity
6.000 N NaaCOa Time of Coeff. of efflux viscosity
Poise Sec. Poise Sec. Poise See. Poise 0.01564 197.26 0.02116 257.03 0.02863 345.63 0.03980 0.00976 107.40 0.01283 135.55 0.01678 175.25 0.02246 89.08 0.00950 108.65 0.01198 72.60 0.00746 0.00584 64.80 0.00647 77.06 0.00794 55.13 0.00530 0.00428 The NazCOs data are taken from Hitohoock and McIlhenny [IxD. ENQ.CHEIM., 27, 461 (1935)l.
Sec. 476.32 226.50 133.75 90.35
Poise 0.05650 0.02994 0.01521 0.00960
b From International Critical Tables.
AND TABLE 111. RESISTANCES
' Sp. conTemp, ductivityb O C. 25.0 35.0
SPECIFIC CONDUCTANCE OF
.
KC1 1.000 N NazCOa ResistCell Resist- Sp. popance constant ance ductivity
Mho Ohms 0,002768 797.42 2.2073 0.003312 663.74 2.1983
Ohms Mho 41.61 0,05305 33.87 0,06490
0.02 N POTASSIUM CHLORIDE AND OF SODIUM CARBONATE5 SOLUTIONS
2.000 N NazCOa
Resist- Sp. popance ductlvlty
3.000 N NszCOs Resist- Sp. conanoe ductivity
4.000 N NazCOa
5.000 N NaPCOa 6.000 N NazCOt Resist- Sp. con- Resist- Sp. con- Resist- Sp. conance ductivity ance ductivity anoe ductivity
Ohms Mho 27.29 0.08088 21.99 0,09997
Ohms Mho 22.86 0.09656 18.16 0,1211
Ohms Mho 21.49 0,1027 16.77 0.1311
Ohms Mho 21.72 0.1016 16.93 0.1298
Ohms Mho 23.17 0,09526 17.59 0.1250
Anhydrous sodium carbonate.
b From International Critical Tables.
0.0567 0.0533
I26
0,0500
1.24
0.0467
I22 I20 I 18 >.
I16
2
I14
t CL
0
2 n (o
-3
0.0433
'"
0.0367
-2
0.0400
0.0333 0.0300
1.12
00267
y 0.0233 ' 0.0200
1.10 IO8 1.06
0.0167
I04
0.0133
1.02
0.0100
1.00
0.98 0.96
0
0.0067 0.0033
1
2 3 4 NORMALITY
5
0.oocQ
6
FIGURE3. SPECIFICGRAVITIESOF WATERAND SODIUM CARBONATE SOLUTIONS AT VARIOUS TEMPERATURES
0
1
2
3 4 NORMALITY
5
6
FIGURE4. VISCOSITY OF WATER AND SODIUM CARBONATE SOLUTIONS AT VARIOUS TEMPERATURES
EMF 1.040
15;
1.035
12.9
1.030
128 12.8
1.025
12.7
1.020
12.6
1.015
12 5 12.5
1.010
12.4
1.005
123 12.3
1.000
12.2
0.13
-
0.12
NORMALITY - E M F
(o
0
I
E
0.11
W
0
= 2V
0.10
5
0.09
3
8 2 0.08 L-
s$j
0.07
0.06 0.05
1
2
3 4 NORMAL1TY
5
6
FIGURE 5. SPECIFICCONDUCTANCE OF SODIUM CARBONATE SOLUTIONS
1
1
2
3 4 NORMALITY
5
1
6
FIGURE6. ELECTROMOTIVE FORCES AND PH VALUESOF SODIUM CARBONATE SOLUTIONS
INDUSTRIAL AND ENGINEERING CHEMISTRY
OCTOBER. 1939 c
TABLEIV.
E. M. F.b
Normality of NaaCOo
0
b
ELECTROMOTIVE FORCES AND PH VALUES OF SODIUM CARBONATE^ SOLUTIONS Trial 1
Trial 2 Average 1.00812 1.00816 1,00809 1.000 1.02094 1.02099 2.000 1.02104 1.02930 1.02931 3,000 1.02932 1.03488 1.03489 4.000 1.03490 1.03804 1.03808 1.03800 5.000 1.03903 1.03895 6.000 1.03010 Anhydroua sodium carbonate. Between normal hydrogen snd calomel electrodes at 25.0' C.
PH
12.27 12.49 12.63 12.73 12.78 12.80
~~
The specific gravity values (Figure 3 and Table I) were nearly straight-line functions of the normalities, and for given normalities nearly straight-line functions of the temperature. Values vary from 1.047 and 1.009 a t 22.5' and 98' C., respectively, for the 1.000 normal, to 1.262 and 1.214 for the same temperatures with the 6.000 normal solution. I n industry large quantities of solution are transported through pipea. Often the concentration is high and the temperatures vary. Viscosity is an important factor in costs.
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Instead of nearly straight-line functions the viscosities increase much more rapidly with higher normalities and decrease rapidly with higher temperatures (Figure 4 and Table 11). At the highest temperature measured, these changes almost compensate one another. The extremes are 0.01201 and 0.00347 poise for the 1.000 normal solution a t 22.5' and 98' C., respectively, and 0.05650 and 0.00960 poise for the 6.000 normal solution a t the same temperatures. Maximum values of specific conductance were obtained at 4 normal (Table 111). The curves in Figure 5 show that the maximum values occur a t about 4.25 normal. The values increase rapidly from 1 to 3 normal. The curves for potential and pH values (Figure 6) rise rapidly with increase of normality and then begin to flatten. The alkalinity of the solutions varies from a pH of 12.27 for the 1 normal to 12.80 for the 6 normal (Table IV). This paper shows that some of the properties of concentrated solutions cannot be predicted from those of dilute solutions. It is worth while to determine experimentally the properties of concentrated solutions of those salts used extensively in technical work.
SEPARATION PROCESSES Analogy between Absorption, Extraction, Distillation, Heat Exchange, and Other Separation Processes' MERLE RANDALL AND BRUCE LONGTIN University of California, Berkeley, Calif.
HEN a number of related fields of technical knowledge have developed independently, it is natural that each field will be supplied with its own distinctive viewpoints and methods of calculation. The recognition of an analogy between a number of fields is valuable in allowing the methods peculiar to each field to be applied in the analogous fields, thus expanding the arsenal of mathematical weapons available in each particular field. The close analogy between distillation and solvent extraction processes was pointed out by Saal and Van Dyck (16, 17) and used by them to develop a new method of solvent extraction. This analogy has since also been used successfully by Varteressian and Fenske and by others (d,4, 15,18) in elaborating new principles of extraction. Although it is now somewhat difficult to disentangle the early history of countercurrent extraction (cf. IO), it is relatively certain that even its earliest stages were considerably influenced by recognition of this analogy. Thus it is safe to
W
The first five appeared in 1938 1 This is the sixth paper in this series. and in February, July, and September, 1939,respectively.
An analogy exists between all types of processes in which the important considerations are those of material and energy balance, diffusion and rates of transfer, and equilibria. Application of this analogy has already permitted experience in fractional distillation to be utilized in developing solvent extractions and similar processes. This paper suggests broader applications of the analogy. Absorption in the case of variable reflux ratio is discussed. The analogy between heat transfer and absorption is brought out, and a concept analogous to the height of a mass transfer unit (H. T. U.) is proposed. say that the development of solvent extraction processes has profited greatly by previous experience in distillation through the aid of this analogy. The graphical methods previously discussed in this series (14) are essentially exact methods of representing complex material and energy balances together with equilibria. BoSnjakovi6 (1) presented methods of carrying out calculations in the H vs. N diagram for cases in which heat flow and diffusion are occurring simultaneously; with respect to this diagram they maintain the position which is held by the standard method of integrating diffusion equations for packed towers with respect to the y vs. x diagrams. Thus the fields of heat transfer, distillation, absorption, extraction, and all others which chiefly involve considerations of material and energy balance, flow of heat, diffusion, and equilibria may be considered analogous with respect to application of these methods.
