PHYSICAL PROPERTIES EVALUATION OF COMPOUNDS AND MATERIALS 1
Conductivity of Sodium Sulfate Solutions Containing Sodium Hydroxide or Sulfuric Acid R. V. LUNDQUIST AND R. W. LEWIS Bureau of Mines, U. S. Department of the Interior, Boulder City, Nev.
T h e conductivity of s o l u t i o n s of sodium s u l f a t e mixed with sodium hydroxide or s u l f u r i c a c i d w a s i n v e s t i g a t e d by t h e B u r e a u of Mines in c o n j u n c t i o n with t h e preparation of s u l f u r i c acid and sodium hydroxide by t h e e l e c t r o l y s i s of sodium s u l f a t e s o l u t i o n s . T h e sulfuric acid w a s used t o l e a c h m a n g a n e s e f r o m i t s low-grade ores; t h e sodium hydroxide w a s u s e d for t h e precipitation of manganese f r o m solution. T h e e l e c t r o l y s i s of sodium s u l f a t e i n a threecompartment c e l l produces t h r e e s o l u t i o n s of different compositions, e a c h of which contributes t o t h e t o t a l c o n ductivity of t h e cell. Conductivity d a t a w e r e obtained for s o l u t i o n s of sodium s u l f a t e , sodium s u l f a t e mixed with sodium hydroxide, a n d sodium s u l f a t e mixed with s u l f u r i c a c i d a t t h r e e l e v e l s of concentration a n d a t t h r e e temperat u r e s for e a c h .
PREVIOUS WORK T h e l i t e r a t u r e reports t h e conductivity of sodium s u l f a t e s o l u t i o n s a t s e v e r a l c o n c e n t r a t i o n s and temperatures, but n o d a t a were found for mixtures of sodium s u l f a t e with s u l f u r i c a c i d or with sodium hydroxide. Mellor (3) r e p o r t s the e q u i v a l e n t conductivity of a 1.ON s o l u t i o n of sodium s u l f a t e t o b e 5 0 . 8 0 ohms-' per l i t e r or 0.05080 ohm-'cm.-' at 18OC. T h e International C r i t i c a l T a b l e s (2) give a v a l u e of 0.0503 ohm-' cm." for t h e s a m e temperature. Stender and S e e r a k ( 4 ) report s p e c i f i c conductivity for sodium s u l f a t e s o l u t i o n s o v e r a c o n s i d e r a b l e range of concentration a t 35OC. T h e s e d a t a a r e plotted i n F i g u r e s 4 and 5 for comparison with t h e d a t a reported i n t h i s paper.
MATERIALS AND EQUIPMENT Analytical reagent-grade c h e m i c a l s w e r e u s e d t o prepare s t o c k s o l u t i o n s . T h r e e s t o c k s o l u t i o n s of e a c h of t h e t h r e e reagents-sodium hydroxide, sodium s u l f a t e , a n d s u l f u r i c acid-were prepared t o normalities of 1.0, 2.0, a n d 2.8. T h e sodium hydroxide c o n t a i n e d a maximum of 1.2% of sodium c a r b o n a t e and t h e sodium s u l f a t e c o n t a i n e d a n 1957
F i g u r e 1.
Specific conductance V S . sodium sulfote replacements for 1N solutions
CHEMICAL A N D E N G I N E E R I N G D A T A
SERIES
69
Table
1. Specific Conductivity of Sodium Sulfate Solutions Specific Conductance, Ohm-' Cm.
NapSO4 Replaced, 70
NaOH
0 50.0
250.0 200.0 187.5 150.0 133.9 125.0 100.0 89.3 75.0 71.4 53.6 50.0 35.7 25.0 17.9 12.5 8.9
100.0
80.0 75.0 60.0 53.5 50.0 40.0 35.8 30.0 28.6 21.4 20.0 14.3 10.0 7.15 5.0 3.57 0.0 3.57 5.0 7.15 10.0
14.3 20.0 21.4 28.6 30.0 35.8 40.0 50.0 53.5 60.0 .75.0 80.0 100.0
62.5 100.0 116.1 125.0 150.0 160.7 175.0 178.6 196.4 200.0 214.3 225.0 232.1 237.5 241.1 250.0 24;. 1 237.5 232.1 225.0 2 14.3 200.0 196.4 178.6 175.0 160.7 150.0 125.0 116.1 100.0 62.5 50.0 0
H&OI
... ... ... ... ... ... . I .
...
...
... ... ... ... ... ... ... . . I
0
0
... ... ... ... ... ... ... ... ... ... ... ... ... ...
8.9 12.5 17.9 25.0 35.7 50.0 53.6 71.4 75.0 89.3 100.0 125.0 133.9 150.0 187.5 200.0 250.0
. . I
I . ,
. I .
2.W Solutions
1.ON Solutions
Solution Volumes, M1. Na2S04
25.2OC.
49.4OC.
74.9OC.
0.1815 0.1559
0.2603 0.2244
0.3398 0.2950
0.1308
... ...
0.1898
... ...
0.2499
0.1062
0.1557
0.2071
...
...
... ... ... ... 0.0821 ... 0.0705 ... ... 0.0598 ... ... ... 0,0644 ... 0.0699 ... ... ...
... I . . . . I I . .
0.1225
... 0.1064 ... ... ... 0.0925 ... ... ...
. I .
0.0909
... ... ...
... ... ... ... 0.1648 ... 0.1446 ... ... ... 0.1264
... ... *.. ... 0.1005 ...
....
0.0874
... ... 0.1180 ...
. . I
0.1327 . I ,
0.1615 0.2126
0.1908 0.2594
I
I
I
0.3
0.4
SPECIFIC CONDUCTANCE Figure 2.
70
Specific conductance V S . sodium sulfate replacement for 2N s 0 1 ~ t i o n ~
INDUSTRIAL AND ENGINEERING CHEMISTRY
. I .
0.1925 0.1716
...
0.1028 . I ,
0.0949
0.1046
0.1150
...
... 0.1417 ... 0.2142 0.2960
0.2858 0.2569
0.3792 0.343 1
... *
I
.
0,1910 0.2103
0.1123
...
. . I
0.4760
0.1754 0.2013
... ...
0.1314
0.1206
0.1103
... ...
0.1518 0.1790
...
...
I . .
... ... 0.3582 ... ...
...
0.1514
. . I
... ...
74.9OC.
... 0.3059 ... ... 0.2695 ... 0.2351 ... 0.2179 ... 0.2040 ... 0.2021 ... 0.1982 ... 0.1930 ...
0.0998
I . .
2.W Solutions
49.4OC.
... 0.2280 ... ... 0.1999 ... 0.1732 ... 0.1599 ... 0.1485 ... 0.1502 ... 0.1514 ... 0.1562 ... ... 0.1623 ...
. I .
. . I
undetermined small quantity of sodium bisulfate. Ordinary d i s t i l l e d water w a s r e d i s t i l l e d in borosilicate g l a s s and boiled j u s t before u s e as t h e s o l v e n t . T h e conductivity of t h e water w a s considered i n s i g n i f i c a n t for t h i s work. T h e Kohlrausch alternating current bridge method w a s u s e d for t h e conductivity measurements. T h e components of t h e apparatus were: a Kohlrausch slide-wire, a r e s i s t a n c e box wound for a minimum of c a p a c i t a n c e and inductance, a microphone hummer h a v i n g a s t a b l e 100CLcycle frequency
0.2
... 0.2435 ...
I . .
I , .
0.0917'
25.2"C.
4 . .
*..
0.1168 . . I
0.1315
... ... I . ,
0.2 783
...
... ... 0.3311 ... ...
.
I
.
0.1900
*..
... ... 0.3689 ... ...
25.2'C.
49.4OC.
...
74.9 O c.
... ...
... ... ... 0.2395 ... *..
... ... ... 0.3631 ... ...
... ... 0.4916 ... ...
0.1948
0.2990
0.4060
. I .
... 0.1779
. . I
. I .
0.1604
0.2738 0.2478
0.3733 0.3409
0.144 1
0.2242
0.3085
... ... 0.1283 ...
... ... 0.2058 ...
*..
...
0.2856
...
0,1199 0.1128 0.1175
0.1899 0.1802 0.1822
0.2640 0.2523 0.2511
0.1227
0.1850
0.2501
0.1334
0.1901
0.1469 0.1611
0.1969 0.2039
0.2468 0.2438
0.1800
0.2153
0.2443
... ...
... ...
... I . .
... *..
... ...
... I . .
... ... 0.2480 ... ... ... . I .
0.2470
0.2812
0.2967
... ... ...
... ...
...
...
*..
.
I
.
*..
... a , .
output, a s i m p l e amplifier unit, earphones, a Washburn high conductivity c e l l , and a c o n s t a n t temperature bath controlled t o f 0.03"C. All component parts, e x c e p t the s l i d e wire, were w e l l s h i e l d e d .
PROCEDURE AND EXPERIMENTAL RESULTS T h e equation L = K/R r e l a t e s t h e s p e c i f i c conductivity L, e x p r e s s e d in ohm-' cm.-', and R , t h e measured r e s i s t a n c e in ohms of t h e solution in t h e conductivity c e l l . K i s t h e cell constant e x p r e s s e d by t h e unit cm.-' and c o r r e c t s t h e geometry of t h e a c t u a l conductivity cell t o that of a standard c e l l . T o determine t h e value of t h e c e l l c o n s t a n t , K , a 1.OOOON solution of s p e c i a l g r a d e chemically pure potassium chloride w a s used. T h e s p e c i f i c conductivity of t h e solution w a s given a s 0.11219 ohm-' cm.-' at 25.2"C. ( I ) and f r o m t h i s v a l u e t h e c e l l c o n s t a n t , K , w a s determined t o b e 33.961 f 0.0145 cm-'. T h i s value w a s u s e d in a l l subs e q u e n t c a l c u l a t i o n s t o derive t h e s p e c i f i c c o n d u c t a n c e of t h e s t o c k s o l u t i o n s and mixtures. T h i s s t u d y w a s on t h e products formed when a solution of sodium s u l f a t e i s fed continuously t o a compartmented electrolytic c e l l . T w o product s o l u t i o n s a r e recovered from w c h a c e l l , o n e rich i n sodium hydroxide and t h e other rich in s u l f u r i c a c i d . E a c h of t h e s e s o l u t i o n s contributes t o t h e total conductivity of t h e c e l l . T o e v a l u a t e individual contributions, appropriate volumes of s t o c k s o l u t i o n s of equal normalities w e r e mixed. For example, on mixing equinormal s o l u t i o n s of sodium s u l f a t e and sodium hydroxide, t h e e n t i r e range of replacement of t h e s u l f a t e ion by equivalent hydroxyl i o n s could be s t u d i e d without c h a n g i n g t h e concentration of t h e sodium ion. Similarly, sodium i o n s were replaced by e q u i v a l e n t hydrogen i o n s on t h e a c i d i c VOL. 2, NO. I
1 0.I
F i g u r e 3.
I I 1 1 I 0.2 0.3 0.4 S P E C I F I C C O N D U C T A N C E ,OHM-’ CM:’
1
I 0.5
Specific conductance V S . sodium sulfate replacement for 2.8N solutions
s i d e by mixing equinormal s o l u t i o n s of sodium s u l f a t e and s u l f u r i c acid for a c o n s t a n t s u l f a t e i o n concentration. E a c h s o l u t i o n mixture w a s placed i n t h e conductivity c e l l and r e s i s t a n c e w a s measured at t h e temperature i n d i c a t e d . E a c h v a l u e for t h e s p e c i f i c c o n d u c t a n c e reported i s a n a v e r a g e of five individual determinations. T h e maximum s t a n d a r d deviation d i d not e x c e e d f 0.00024 for any s e t of five v a l u e s . F u r t h e r , t h e majority of s e t s showed a d e v i a tion l e s s t h a n i 0.00010. T a b l e I records t h e s p e c i f i c c o n d u c t i v i t i e s of sodium s u l f a t e s o l u t i o n s mixed w i t h sodium hydroxide or s u l f u r i c acid at t h r e e l e v e l s of concentration a n d a t t h r e e temperat u r e s for e a c h . T h e f i r s t column s h o w s t h e fraction of sodium s u l f a t e , e x p r e s s e d a s a percentage number, that w a s r e p l a c e d by sodium hydroxide on t h e c a u s t i c s i d e or by s u l f u r i c a c i d on t h e a c i d i c s i d e . T h e next t h r e e c o l u m n s under “ s o l u t i o n v o l u m e s ” show t h e volumes of s o l u t i o n s u s e d for e a c h fractional replacement. T h e remainder of t h e t a b l e records t h e s p e c i f i c conductivity of e a c h s o l u t i o n mixture a t t h r e e different temperatures. T h e c u r v e s i n F i g u r e s 1, 2 , and 3 s h o w graphically t h e s p e c i f i c conductivity v a r i a n c e with temperature, with s a l t c o n c e n t r a t i o n s , and with c h a n g e s in i o n replacements for both t h e c a u s t i c and a c i d i c s i d e s of neutral sodium s u l f a t e .
T h e v a r i a t i o n s of c o n d u c t i v i t y a s i l l u s t r a t e d by t h e s e c u r v e s a r e c o n s i s t e n t with what might be e x p e c t e d . In t h e c a u s t i c replacement s e r i e s t h e conductivity c h a n g e i s nearly a l i n e a r function of t h e sodium hydroxide replacement. As t h e sodium hydroxide concentration i s i n c r e a s e d , t h e s u l f a t e i o n s a r e replaced by hydroxyl i o n s , which h a v e a much greater i o n i c mobility, t h u s i n c r e a s i n g t h e cond u c t i v i t y of t h e s o l u t i o n . T h e conductivity c h a n g e s d u e t o t h e s u l f u r i c a c i d replacement a r e not s t r a i g h t l i n e s , b e c a u s e t h e formation of b i s u l f a t e ions c o n t r i b u t e s t o t h e t o t a l effect. T h e b i s u l f a t e ion partly i o n i z e s t o hydrogen a n d s u l f a t e i o n s , but with t h e e x c e s s s u l f a t e ions p r e s e n t t h e equilibrium i s s h i f t e d a n d t h e b i s u l f a t e i o n s tend t o remain a s s u c h . C o n s e q u e n t l y t h e t o t a l number of i o n s in s o l u t i o n a r e a c t u a l l y d e c r e a s e d , and t h u s t h e conductivity i s d e c r e a s e d . T h i s d e c r e a s e i s partly offset by t h e p r e s e n c e of hydrogen i o n s which h a v e a very high mobility. T h e i n t e r a c t i o n of hydrogen and s u l f a t e i o n s i s greater a t t h e higher temperatures. After a l l of t h e s u l f a t e ions h a v e b e e n converted t o b i s u l f a t e i o n s , t h e c o n ductivity i n c r e a s e s rapidly a s t h e hydrogen i o n s i n c r e a s e .
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Temperature V S . specific conductance for sodium s u l f a t e solution
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Concentration V S . s p e c i f i c conductance for sodium s u l f a t e solutions
F i g u r e 4 s h o w s t h e plot of s p e c i f i c conductivity vs. temperature for pure sodium s u l f a t e solutions. Similar c u r v e s may be drawn for a n y other particular ion replacement. Another family of c u r v e s may be drawn by plotting s p e c i f i c conductivity a g a i n s t concentration. Figure 5 s h o w s o n e member of t h i s family, t h a t for pure sodium sulfate solutions.
SUMMARY T h e c o n d u c t i v i t i e s of mixtures of pure s o l u t i o n s of sodium s u l f a t e , sodium hydroxide, and s u l f u r i c acid w e r e determined at t h r e e l e v e l s of s a l t c o n c e n t r a t i o n s and a t three temperatures for e a c h concentration. T h e r e p l a c e ment of s u l f a t e i o n s by e q u i v a l e n t hydroxide i o n s i n c r e a s e d the s p e c i f i c conductivity with i n c r e a s i n g replacement. At r o o m temperature t h e e q u i v a l e n t replacement of sodium i o n s with hydrogen i o n s a p p e a r e d t o i n c r e a s e t h e s p e c i f i c conductivity, but a t higher temperatures a tendency w a s noted for t h e s p e c i f i c conductivity t o remain c o n s t a n t or t o d e c r e a s e slightly as t h e composition of t h e solution approached t h a t of sodium bisulfate. After t h a t composition CHEMICAL AND ENGINEERING DATA SERIES
71
w a s p a s s e d t h e s p e c i f i c conductivity i n c r e a s e d a g a i n with i n c r e a s i n g hydrogen ion concentration.
ACKNOWLEDGMENT T h e authors are grateful for t h e many helpful s u g g e s t i o n s and c o n s t r u c t i v e criticism offered by Delwin D. Blue, Boulder C i t y Station, and by Harry C. F u l l e r , M a n g a n e s e Section. To t h e s e and t o many o t h e r s not mentioned but who contributed indirectly, t h e authors e x p r e s s t h e i r appreciation.
LITERATURE CITED (1) Harned, H. S., Owen, B. B., ACS Monograph S e r i e s , No. 9 5 , pp. 137-8, Reinhold, N e w York, 1943. (2) International Critical T a b l e s , vol. VI, p. 236, McGraw-Hill, N e w York, 1929. (3) Mellor, J. W . , “Comprehensive T r e a t i s e on Inorganic and T h e oretical Chemistry,” v o l . 11, p. 670, Longmans, Green, N e w York, 1941. (4) Stender, W. W., Seerak, I. J., T r a n s . Electrochem. S O C . 68, 4 9 5 (1935). R e c e i v e d for r e v i e w August 16, 1956. 1957.
Accepted February 20,
Solubility of Acrylonitrile in Aqueous Bases and Alkali Salts ELIAS KLEIN, J. W. WEAVER, AND BEVERLY G. WESRE Southern Regional Research Laboratory, New Orleans, La.
D u r i n g a study of t h e reaction i n which cotton c e l l u l o s e w a s c y a n o e t h y l a t e d with acrylonitrile u s i n g a q u e o u s a l k a l i b a s e s a s c a t a l y s t s , t h e s o l u b i l i t y of acrylonitrile i n a q u e o u s s y s t e m s w a s required. S i n c e t h e liquid p h a s e a s s o c i a t e d most intimately with t h e cotton c e l l u l o s e during t h e reaction i s a dilute a q u e o u s solution of sodium hydroxi d e or other b a s e , t h e solubility of t h e acrylonitrile i n t h i s p h a s e w a s believed t o b e a determining factor in both t h e r a t e of t h e reaction and t h e e x t e n t of cyanoethylation a t equilibrium. T h e solubility of acrylonitrile in water h a s been reported for various temperatures ( I ) , but no solubility d a t a for acrylonitrile i n v a r i o u s a l k a l i a n d s a l i n e s o l u t i o n s could b e found.
MATERIALS USED T h e acrylonitrile w a s of commercial grade, containing
0.8% of water. In order t o f a c i l i t a t e reading of t h e i n t e r f a c e with
a q u e o u s l a y e r s t h e acrylonitrile w a s colored with
0.005% Celliton F a s t R e d GGA Ex. Conc. (Pr. 236).
(Pr.
2 3 6 refers t o t h e prototype d y e number l i s t e d in t h e AATCC Yearbook for 1955.) All a l k a l i hydroxides and s a l t s were of reagent grade, e x c e p t Naxonate G , a commercially availa b l e mixture of xylene s u l f o n a t e s .
PROCEDURE B e c a u s e acrylonitrile r e a c t s with water i n t h e p r e s e n c e cf b a s e s , i t w a s n e c e s s a r y t o use a solubility determination procedure not b a s e d on equilibrium measurements. T h e measurements were carried o u t a t 2 5 ” i 1 C. i n a n a i r bath. T h e t e c h n i q u e s employed a r e e s s e n t i a l l y t h o s e reported by Booth a n d E v e r s o n ( 2 ) i n their study of hydrotropic s a l t s . In t h e procedure adopted, 4 5 m l . of v a r i o u s conc e n t r a t i o n s of a l k a l i b a s e s w e r e weighed into stoppered, graduated sulfonation b o t t l e s (ASTM D 875-46T); a m e a s -
72
INDUSTRIAL AND ENGINEERING CHEMISTRY
ured volume of acrylonitrile w a s then added rapidly, and t h e b o t t l e s were s e a l e d and tumbled end over end. Thirty minutes a f t e r t h e addition of acrylonitrile t h e tumbling w a s stopped and t h e volume remaining w a s read on t h e gradua t e d s c a l e of t h e bottle. Thereafter readings were t a k e n every 15 minutes until t h e residual acrylonitrile w a s less than 1.0 ml. T h e c h a n g e i n t h e volume of acrylonitrile w a s d u e t o two c a u s e s . T h e f i r s t , a rapid c h a n g e complete in less than 30 minutes, w a s d u e to t h e solution of t h e acrylonitrile in t h e a q u e o u s p h a s e . T h e s e c o n d , a n d slower change, w a s due to t h e hydration of acrylonitrile t o e t h y l e n e cyanohydrin. A s t h e a q u e o u s p h a s e w a s s a t u r a t e d with r e s p e c t t o acrylonitrile during t h e e n t i r e measurement period, a n d t h e b a s e concentration remained e s s e n t i a l l y unchanged, t h e r a t e of acrylonitrile hydration w a s evidently z e r o order. A plot of t h e volume of acrylonitrile remaining vs. time w a s found t o b e linear. Extrapolation of t h i s plot t o zero time permitted a correction t o b e made for t h e l o s s of acrylonitrile d u e t o reaction, and yielded t h e volume of acrylonitrile d i s s o l v e d i n t h e a q u e o u s phase. Use of t h e density of t h e acrylonit r i l e and t h e known weight of water i n t h e flask allowed calculation of t h e molality of acrylonitrile i n t h e a q u e o u s phase. When both a l k a l i b a s e s and s a l t s were p r e s e n t simultaneously, t h e s a m e procedure w a s followed. T h e a q u e o u s b a s e w a s weighed into t h e f l a s k s , a n d w e i g h t s of t h e s a l t c a l c u l a t e d t o give a c o n s t a n t molality of s a l t solution w e r e added. When t h e solubility of acrylonitrile w a s determined i n s a l t s o l u t i o n s alone, t h e previous method w a s not n e c e s sary. Weighed amounts of s a l t s o l u t i o n s were p l a c e d i n t h e f l a s k s and increments of acrylonitrile were added until a s e c o n d p h a s e persisted. T h e s o l u t i o n s were tumbled for 30 minutes between a d d i t i o n s of acrylonitrile. VOL. 2, NO. I
