Viscosity Nornographs for Alkaline Solutions D. S. DAVIS Dale S. Davis’ Associates, Watertown, Mass.
QH
ITCHCOCK and McIlhenny (1) presented the first extensive data on the viscosities of aqueous solutions of sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate, together with a study of the viscosities of mixtures of solutions of sodium hydroxide and sodium carbdnate and of potassium hydroxide and potassium carbonate. Their investigation merits particular attention in view of the industrial importance of these alkalies and because of the need for reliahle viscosity data in connection
i
with the design of equipment where calculation of gas absorption rates and heat and fluid flow must he made. Their studies were conducted a t temperatures of 20°, 30°, and 40” C., and viscosities are given for concentrations of 0.5, 1, 2, 3, 4, 5 , 6, 7, and 8 gram-equivalents per liter of solution. I n the case of mixtures of sodium hydroxide and
i
/6
40
14
I2
38
36
4
c
I
08 07
0.7
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INDUSTRIAL AND ENGINEERING CHEMISTRY
of the solution in centipoises. These relationships form the basis of Figures 1 and 2. For convenience the data for sodium hydroxide and sodium carbonate are combined in Figure 1, and Figure 2 presents the potassium hydroxide and potassium carbonate data in compact form. I n Figure 1 the broken line a t the left shows that a sodium hydroxide solution containing 2 gram-equivalents of solute per liter has a viscosity of 1.225 centipoises a t 30" C. The dashed line a t the right indicates that the viscosity of a 4 A; solution of sodium carbonate is 2.29 centipoises a t 33" C. I n Figure 2 the broken lines a t the left and right, respectively, show that the viscosity of a 4 11; potassium hydroxide solution is 1.43 centipoises a t 25 .' C., and that the viscosity-
-1
.'
\
\
\
\
\
2
0.7
fi9. 2
sodium c a r b o n a t e solutions, the volume percentages of the latter are 26.5, 50.6, and 74.7;for mixtures of potassium hydroxide and potassium carbonate solutions, the volume percenta g e s of t h e l a t t e r component are 27.7, 53.7, and 75.9. There is evident need for convenient interpolation means which shall be rapid and accurate. It is the purpose of this paper to present linecoordinate and nomographic charts which meet these requirements and thus extend the usefulness of the original data.
A
/ '
I N THE case of Y sodium hydroxide solutions, log
( p - 0.4) is linear with temperature over the narrow range between 20Oand 40" C.; for the other pure alkaline s o l u t i o n s , log p is linear with temperature, where p is the viscosity
0' ftg.
3
of a 5 N solution of potassium carbonate is 1.66 centipoise$ at 35" c. At 20' C . Figures 1 and 2 agree exactly with the original data; aboye this temperature the discrepancies average no more than about one per cent. The convenience of interpolationalongcloselygraduated scales more than compensates for the slight loss in accuracy.
pd
A -/v
V/scar/ty
of
KOH Joolh.
and K,CO, 5olh.
-4
;I 4:
1.3
\
+
= PI (1 - Y) P2 y p = viscosityof PI, p~ =
/
/
AS POINTED out
where
M / x t u e cf
N
by Hitchcock and McIlhenny, noideal lam has been proposed to e n a b l e calculation of the viscosity of mixtures of alkaline solutions from the viscosities of their components and the percentage composition. The assumption of a d d i tivity of viscosities according to the expression, P
p, Cent i p 0 i . q
A Key: H% - y - A
-"
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INDUSTRIAL .4KD EXGINEERING CHEMISTRY
ALGUST, 1936
0'
mixture viscosities
of hydroxide a n d
carbonate
y =
solutions, respectively, at same concentration volume fraction of carbonate solution
Fig. 9
leads to errors of as much as 10 per cent in the case of concentrated solutions and must be rejected as unsatisfactory. The equation suggested by Kendall and Monroe's expression (2) which holds for a wide variety of binary liquid mixtures including lubricating oils, is somewhat better but not entirely adequate. For mixtures of sodium hydroxide and sodium carbonate solutions the equation P
=
P1
holds very closely, as indicated by the following table which lists deviations of the calculated values from the original data for total normalities of 0.5 to 8 (Equation 1): Deviation in Visohsity 7'30' C. ;os c. 1.1 2.1 0.7
-.4v. Y
0.265 0.505 0.747
200
c.
0.8
1.5
0.1
0.9
0.4 0.3
The expression is admittedly empirical but has a precedent
in an identical equation proposed by Wennberg and Landt ( 3 )for the cuprammonium viscosity of binary rag blends. The equation can be handled most conveniently by means of Figure 3, the use of which is illustrated as follows: What is the viscosity of a mixture of sodium hydroxide and sodium carbonate solutions of the same concentration when their viscosities are 4.40 and 6.69 centipoises, respectively, and the composition of the mixture is 60 per cent sodium hydroxide solution by volume and 40 per cent sodium carbonate solution? The ratio of the two viscosities is (6.69/4.40) or 1.52. Connect this value on the scale at the left with 40 per cent on they scale and note the intersection with the A axis. Connect this latter point with 4.40 on the p l scale and read the desired value as 5.20 on the p scale.
2 THE expression
Ir = Pl
(E)"
correlates the data for mixtures of potassium hydroxide and potassium carbonate solutions a t the same concentration. I n this case ?a is defined as 0.791 y between y = 0 and y = 0.55, and as (1.2556 y - 0.2556) between y = 0.55 and
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y = 1.00, although no cognizance need be taken of the varying definition of n in using Figure 4, designed to solve the equation rapidly and accurately. The following table indicates the degree of agreement between the empirical expression and the original data for total normalities of 0.5 to 8 (Equation 2) : ---Av. ?Go
C.
Deviation in Viscosity, %-30' C. 40' C.
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the same concentration, and the mixture contains 40 per cent potassium hydroxide solution by volume and 60 per cent potassium carbonate solution. What is the viscosity of the mixture? The ratio of the viscosities, p q j p i , is (2.553/1.850) or 1.380. Following the key, connect 1.380 on the scale a t the left with 60 per cent on the y scale and note the intersection with the A axis. Connect this point with 1.850 on the p1 scale and read the desired value on the p scale as 2 . l i centipoisee.
Literature Cited The use of Figure 4 is illustrated by the following example:
-4solution of potassium hydroxide with a viscosity of 1.880 centipoises is mixed with a solution of potassium carbonate having a viscosity of 2.553 centipoises. The solutions have
(1) Hitchcock a n d McIlhenny, ISD. ESG. CHEY.,27, 461 (1935). ( 2 ) Kendall and Monroe, J. -4m.Chem. SOC.,39, 1787 (1917). (3) V e n n b e r g a n d Landt, Paper Trade J . , 93,202 (1931). RECEITEDl l a y 5 , 1936.
Potash from Polyhalite by Reduction Process F. PRAAS
Extraction of Potassium and the Production of Potassium Carbonate'
AND EVERETT P. PARTRIDGEz Nonmetallic Minerals Experiment Station, U. S. Bureau of Mines, Rutgers University, New Brunswick, N. J.
of potassium carbonate, both from the potassium sulfide extract liquor and from the solid residue from the extraction step, is described.
Diffusion-Column Extraction PROCESS for reducing polyhalite (K2S04JlgS04.2CaSOa2H20) and extracting the potassium sulfide from the reduction prodiict with water has been described ( 2 , 7 ) ,and the use of natural gas in the reduction step has been studied in some detail ( 3 ) . Information concerning the extraction of polyhalite reduced with natural gas in a rotary kiln is now presented to supplement the earlier data ( 2 ), indicating that high recoveries and concentrations were possible. I n addition, the prodiiction
A
1 Previous papeis in this series appeared in September, 1932, a n d February, 1936. 2 Present address, Hall Laboratories, Inc , Pittsburgh, Pa
The water extraction of polyhalite reduced with converted natural gas, yields, with high recovery, solutions containing 31 per cent potassium. A t 30" C. the extracts are essentially solutions of potassium monosulfide with smaller amounts of the hydrosulfide and carbonate, and a t the higher concentrations are saturated with respect t o potassium carbonate as a solid phase. A t higher temperatures the amount of hydrosulfide increases, and the carbonate decreases as a result of the hydrolysis of calcium sulfide and the
K h e n polyhalite, reduced in the 18-8 chrome-nickel steel kiln ( 3 ) ,mas extracted in a diffusion column to approximate countercurrent operation and to give an indication of the maximum concentration permissible under the conditions of the necessary high solid-liquid ratio, the results designated under experiment 1, Table I, were obtained. The composition of the discharged solution is given in Figure 1. From the shape of the curve it is seen that a maximum concentration was not reached, although the concentration of potassium at zero time corresponded to 26.9 per cent. ?;early all of the carbonate ion was dissolved, since the amount in solution--0.161 mole-corresponded closely to the total of 0.173 mole
double decomposition between calcium sulfide and potassium carbonate. Potassium sulfide may serve as a starting point for the production of a variety of industrial chemicals. On carbonation a yield of 320 pounds of potassium carbonate per short ton of polyhalite is obtained. The extract residues when processed with the potassium chloride from the sylvinite deposits will yield additional quantities of potassium carbonate together with calcium chloride, magnesium carbonate, and hydrogen sulfide.
