VISCOSITIES O F SOME MONOVALENT SALTS OF HIGHER FATTY ACIDS I N ORGANIC SOLVENTS BY MATA PRASAD
In a previous paper from this laboratory Bhatnagar and Prasadl have determined t.he electrical conduclivities of some monovalent salts of higher fatty acids in organic solvents and in the fused state. On plotting the equivalent conductivity against dilution in litres they have shown there that the curves obtained are straight lines and not parabolas as required by Ostwald's dilution law. It was first suggested by Wiedemand and later on by Arrhenius3 that the mobility of an ion is a function of the fluidity of the solution and decreases with an increase in viscosity. Consequently the conductivity of a solution is greatly altered by the viscosity of the solution. The viscosity correction, made by Alemcke and Pissarjewski' on the assumption that the conductivity is directly proportional to the dissociation and inversely proportional to the viscosity is of the form== I* Lq?! . (1)
Pa
70
where a represents the degree of dissociation, pv and qv, respectively, the equivalent Conductivity and viscosity of the solution at the dilution of V litres ana pa and qo, respectively, the equivalent conductivity and viscosity of the solution at definite dilution. The same conductivity-viscosity expression was derived by Arrhenius on simple proportionality assumptions. The present investigation is devoted to the study of the viscosities of the soap solutions in organic solvents and the data so obtained can be utilised to apply the correction to the conductivity values described in the previous paper. Incidentally the results obtained here have also been utilised to verify the various viscosity-concentration relations that have boen put forward by Einstein, Hatschek, Smoluchowski and Arrhenius.
Experimental The soaps used in the investigation were sodium and potassium palmitate, sodium and potassium stearate and potassium oleate. They were prepared by mixing alcoholic solutions of sodium and potassium hydroxides with alcoholic solutions of the corresponding acids in molecular proportion5. The alcohols tried were ethyl, normal-butyl and iso-butyl alcohols. They were obtained by distilling Illerck's pure alcohols and collecting;the fraction distillCf. Kolloid-Z. 33, 279 (1923). Pogg. Ann. 99, 228 (1856). 3 Z. physik. Chem. 9, 49.5 (1892). Ibid. 52, 479 (1905). 6 Cf. Bhatnagar and Prasad: loc. cit.
63 7
VISCOSITIES O F SOAPS I N ORGANIC SOLVENTS
ing over at the boiling point. Precautions were taken to remove the traces of water by keeping them in soda-lime and quick-lime and afterwards in anhydrous copper sulphate for about a week. They werc tested free from aldehyde by the alkali test. The solutions were prepared by out weighing exactly known quanitites of soaps and dissolving t,hem in known quantities of alcohols. They were liept in glass-stoppered bottles free from contact with air. The viscosity measurements were made in a viscosimeter of the common capillary pattern of W. Ostwald. The size of the capillary and the volume of the bulb were so chosen that a suitable time of flow of the solutions was obtained. It was about 4 minutes in the case of ethyl alcohol and 7 andg minutes, respectively, in the case of n-butyl and iso-butyl alcohols. The viscosimeter was kept in a vertical position by means of two plumb lines hanging from the support holding the viscosimeter. The viscosimeter was kept a t a constant temperature at 3oOC. All care was taken to remove the traces of grease or impurity in the viscosimeter. In order to achieve this the instrument was washed with soap solution, alkali solution, potassium dichromate mixture and distilled water before and after each observation. The amount of water remaining in the viscosimeter was removed by rinsing it several times with alcohol and drying it in a current of air.
A fixed volume of solution was always introduced in the viscosimeter from a pipette, and after being raised to the upper mark by sucking, was allowed to run through the capillary tube. The viscosimeter was allowed to stand in the bath for a sufficient time to acquire the temperature of the bath, because, as is well known, the viscosity decreases very rapidly with the increase in temperature. The readings were taken when the time of flow became constant which was measured by an accurate stop-watch. The density of the solutions was measured by means of the specific gravity bottle. The solutions were carefidly filled in the bottle and the air bubbles removed from it. It was then kept in the constant temperature bath at 3ooC for about two minutes and quickly weighed. From the constants of the bottle determined before hand the specific gravities of the solutions were calculated. The relative viscosities of the solutions with respect to the solvent were then calculated from the formula-
where t oto , and do are the viscosity, time of the flow and density, respectively, of the solvent arid qv, t and d the corresponding values for the solution. The viscosity of a colloidal solution according to Einstein' and Hatschek,2 is given by rlv=17o(I+k~)
Ann. Physik, 19, 289 (1906);34, 591 (1911). Kolloid-Z. 7, 310 (1910);8, 34 (1911).
(31
63 8
MATA PRASAD
where cp is the volume-fraction of the disperse phase per unit volume of the solution and k a constant having values 2 . 5 according to Einstein and 4.5 according to Hatschek. Another formula was empirically derived by Arrhenius‘ for the viscosities of solutions and is represented as
1%
(4)
=
%/VO
where c is the volume-fraction of the solute per unit volume of the solvent and 8, a constant. I n tables given below cp represents the mass of the solute per unit volume of the solution and is given in column 2 . The values of rly/r0obtained experimentally are shown in column 3, while those obtained by calculation from Einstein’s and Hatschek’s formula are given in columns 4 and 5 respectively. The values of 8, a constant referred to the equation (4), are shown in column 6, its value as determined by Arrhenius being 0.01086.
TABLE I Viscosity of Potassium Palmitate in Ethyl Alcohol at 30°C. 2 3 4 5
I
Concentrations M,‘3 0 M/60 M/80
qdqo
‘p
0 . ooyS
M/Io~
0.0049 o ,0036 o ,0029
M/I42
0,002I
gms ” ”
” ”
Ob8
Cal .0245
qv/qo
1.0287 I ,0140 I .0087 I .0065 1.0033
I
I .0122 I
,0090
qv/qo I I
I
I .0072
I
I ,0052
I
6
e
Cal
.0441 .or220 .0162 ,0130 .0094
1,255 I ,225
,028 0.931 0.667 I
TABLE I1 Viscosity of Potassiuni Stearate in Ethyl Alcohol at 3oOC. 2 3 4 5
I
Concentrations w 3 0 M/60
M/80
M/IOZ WI42
Obs .0276 ,0193
qv/qo
‘p
0.0107 gms
I
0.00j3
”
I
0.0040 o ,003 I 0.0023
”
I ,0101
Cal ,0267 ,0134
qv/m I I
I ,0100
”
1.0066
I
.0079
”
I .0022
I
,0056
6
e
m / q 0 Cal
I
,0481 .0238
I
.0180
I
1.0139 .or03
I
I . 103 ‘ 54.7 1.075
1
0.903
0,435
TABLE 111 Viscosity of Potassium Oleate in Ethyl Alcohol at 3ooC. I
3
2
Concentra t,ions M/30 M/60
w/qo
‘p
M/80 M/Io~
0.0107 gms .OOS3 ” 0.0040 ” 0.0031 ”
WI42
0.0022
I
0
”
. Obs
e
,0267 ,0132 I .or00
,0481 ,0238 I ,0180 I ,0139 1.0099
0.925 I .246
,0229
I I
,0080 .OO~I
I
,0077
I
.005j
I
I
1.0027
6
q v l m Cal
I . O I ~
I
5
4
w / m Cal
hledri. VetenRk. Nobelinstitrit. 3, KO.13 (1916).
I I
0.850
0.677 0.545
639
VISCOSITIES O F SOAPS IN ORGANIC SOLVENT8
TABLE IV Viscosity of Sodium Stearat,e in Ethyl Alcohol at 3oOC. 2 3 4 5
I
Concentrations M/30 M/60 M/80
M/IOZ M/I42
c
qviqo
o ,0102 gms 0 ,0051
0.0038 o ,0030 0.002 I
Oba
qvlqo
Cnl
e
1.0459 1.0229
1,343 1.804 1.237 1.067 0.190
”
1.0321 1.0216
”
1.0110
1.0095
1.0171
’)
r.0075
”
1.0010
1.0075 1.0052
1.or35 1.0094
1.0255 1.0127
6
q v / m Cnl
TABLE V Viscosity of Sodium Palmitate in Ethyl Alcohol at 3oOC. 2 3 4 5
I
Conccnt rat ions M/3o M/60
M/80 M/I02
M/I42
”
1.0076 1.0061
Cd 1.0232 1.0115 1.0087 1.0067
’)
1.0025
1.0050
rp
~ / q Ohs o
o ,0093 gms 0.0046 ” 0.003 5 ”
1.0210
o ,0027 0.0020
1.0121
qv,lqo
qv/qo
Cnl
1.0418
6
e
1.0121
0.968 1.131 0.914 0.926
1.0090
0.550
1.0207
1,0157
TABLE VI Viscosity of Potassium Palmitate in n-Butyl Alcohol at 3oOC. I
3
2
Concentrations M/80 M/90
M/IOO M/IZO M/ I 60
c
qv,/qo
0.003 7 gms 0.0033 ”
5
4 Ob5
1.0257 1.0204 1.0160
0.0030
”
0.0025 o .0019
”
1.0117
’)
1.0064
Cnl 1.0092 1.0082 1.0075 1.0062 1.0047
qv.llto
6
~ v / ~ C do
e
1.0166 1.0148 1.0135
2.973 2.667 2.267
I.OIIP
2.00o
1.0085
1.421
TABLE VI1 Viscosity of Potassium Stearate in n-Butyl Alcohol at 3oOC. I
Concentrations
M/80 w 9 0
3
2
0.0040 gms o ,0036 ” 0 . 0 0 32 ”
M/IOO M/IZO
0.0027
M/160
0.0020
O h 1.0314 1.0249
qvlqo
rp
)’
)’
5
4 Tvlqo
Cal
1.0100
qvlqo
6 Cal
1.0180 1.0162 1,0144
1.0145
1.0090 1.0081 1.0067
1.0121
1.0103
1.0050
1.0090
1.0208
9
3.325 2.805
2.782
2.296 2.201
640
MATA PRASAD
TABLE VI11 Viscosity of Potassium Oleate in n-Butyl Alcohol a t 3oOC. I
3
2
Concentrations M/8o M/9o
P
mjqo
M/IOO M/IZO
0.0040gms 0.003 5 ” 0.003 2 ” 0.0027 ”
M/160
0.0020
”
5
4 Obs
w / q O
Csl
1.0222
1.0100
1.0177
1.0087 1.0080 1.0067 1.0050
1.0127
1.0085 1.0046
6
Cal 1.0180 1.0157 1.0140
e
w/qO
1.0121
1.0090
2.374 2.171
1.719 1.333 0.950
TABLE IX Viscosity of Sodium Stearate in n-Butyl Alcohol a t so°C. I
Concentrations
M/80 M/90
2
3
4
P
m / m Obs
w h o Cal
0.0038 gms 0.0034 ”
iv/Ioo
0.00~0”
M/120
0.0025
”
M/160
o .0019
I’
1.0235 1.0198 I ,0156 1.0123 I ,0090
1.0095 1.0085 I ,0075 1.0062 I ,0047
5 m h o Cal
e
1.0171 1.0153
2,500
I
,0135
I.OIIP I
.0085
6 2.658 2 .
zoo
2.081 2
.ooo
TABLE X Viscosity of Sodium Pnlmitate in n-But,yl Alcohol at 3oOC. I
3
2
Concent,rRtions
5
4 Obs
w , / mC d
1.0184 1.0168 1.0142
1.0087 1.0077 1.0070
1.0057
wlqo
P
M/8o M/90
o .0035 gms 0 . 0 0 3I ”
M/IOO M/IZO M/ I 60
0,0028
”
o ,0023 0 , 0 0 17
”
1.0120
’)
I
.+0073
I
.0043
w/qO
G Cal
1.0157 1.0139 1.0126 1.0103 I .0076
9 2.252
2.322 2.178 2.261 I .449
TABLK SI Viscosity of Potassium Oleate in Iso-P,utyl Alcohol at 3oOC. I
Concentratinns
3
2
qv/m
P
5
4 Obs
w / q O
Cal
1.0177
1.0100
1.0122
1.0087
&I/IO0
0.0040gms 0.003 5 ” 0.0032 ”
M j I P O
0.0027
”
1.0051
M/160
0.0020
”
I
M/80 w 9 0
I
.0079 ,0035
I
.008o
1.0067 I
.005o
w / q O
6 Cal
r.0180 1,0157 I
.0140
1.0121
I
,0090
e 1.900 1.515 I .063
0.778 0.750
VISCOSITIES O F SOAPS I N ORGANIC, SOLVENTS
641
Discussion of Results The viscosities of five different soaps have been measured at five dilutions in ethyl, n-butyl and iso-butyl alcohols and the values so obtained have been compared with those calculated from Einstein’s and Hatschek’s formula. The results indicate that the calculated values (on Einstein’s formula) approximate more closely to the observed values at low concentration of the solute. This is in agreement with the theoretical assumptions on which the formula was derived. It will be seen froni Tables I-XI that the agreement between the calculated and observed values is more exact at concentrations M / 8 0 and M/IOZin solutions in ethyl alcohol and a t concentrations M/12o and M/160 in solutions in n-butyl alcohol. The results calculated with K equal to 4.5 (Hatschek’s value) are in better agreement with the experimental results in the case of solutions in n-butyl alcohol than in ethyl alcohol. As will be noted from above tables, the values of the constant calculated from formula (4) are; in all cases examined here, greater than the values found by Arrhenius. Moreover the value of the constant has been found to vary with the nature of the solute anti the solvent. Ethyl alcohol is knowii to consist of strongly associated molecules in concentrated state which get dissociated on dilution. The results of Horibal of the viscosity of aqueous solutions of ethyl alcohol show that the quotient log q/cl decreases with increasing concentration cl. The same was observed by Baker2 with solutions of nitrocellulose in acetone. But the results of present investigation show that in almost all cases the Arrhenius constant, I
that is, quotient -log c
qv/qo increases with increasing concentration.
Occasionally the solutions were allowed to stand for about a week to observe any change that may take place in the nature of the solutions with time3. But in no case any alteration in the time of flow was experienced. The viscosity correction was applied to the conductivity values according t o the formula ( I ) and the results ohtained are shown in Tables XII-XVI. The relation between pv qv qo and V, volume in litres containing one gram-molecule of the solute, still gives a straight line curve betwcen the range of di1utio.m 30 to 160 litres considered here.
Ethyl Alcohol
V 30 60 80 I02
142
IV
.
59 30.81 33.33 37.53 42.36 27
P V . l)v!qo.
28.38 31.24 33.61 37.76 42.49
V 80 90 IO0
11-RutgI .4lcohol MV.
4.552 4.967 5 . I35
I20
5.759
I 60
6.665
IV. q v ’ T O .
4.669 5.069 5.216 5.826 6.707
642
MATA PRASAD
TABLE XI11 Ethyl Alcohol V.
PV.
30 60
31.54 42.46 43.07 47.90 58.05
80 IO2
142
V.
32.41 43.27 43 .so 48 ' 19 58.19
80 90 IO0
5,520
I20
6.308 8.028
PV. rlV/?O
v.
Ethyl Alcohol
V.
30 60 80 I02
142
v. 30 60 80 102
142
PV.
22.22
28.80 32.71 36.92 46. I O
'
22.74 29.24 32.96 37.10 46.23
Ethyl .Alcohol PV
.
25.87 30.81
36.80 38. I7 43.54
PV. qvlqo
26.70 31.47 37'19 38.45 43.58
Ethyl Alcohol
V.
PV
30
21.22 30.11
60 80 I02
142
n-Btityl Alcohol
PV. q v l t o
PV.
WIT0
21.66 30.47
-
--
36.32 43.54
36.53 43.65
I 60
80 90 IO0
PV.
5.386 5.399
PV.
4,307 4.620 4.906
I20
5.520
6.540
80 90 IO0
I20 I 60
V.
80 90 IO0 120
I 60
qv,iqo.
5 555 '
5.533 5.633 6.397
8 . I10
n-Butyl Alcohol
160
v.
PV.
PV. v v / m
4,403 4.70' 4.968 5.585 6.569
n-Btltyl Alcohol PV
4.206 4.319 4,329 4.999 6.422
PV. W l 8 0 .
4.304 4.404 4.395 5.060 6.477
n-Butyl Alcohol PV
3.924 4.227 4.505 4.906 5.987
PV. Itv/qo
3.996 4,297 4.568 4.966 6.030
VISCOSITIES OF SOAPS IN ORGANIC SOLVENTS
643
The degree of dissociation could not be determined owing to want of the values of ,urn which, as the work of Mahin, Kreider and others has shown, occurs generally a t dilution of 50,000 liters and for the measurement of which the Kohlrausch bridge with ordinary buzzer and telephone is unsuitable. More work on this line will be done over a large range of dilutions to collect sufficient data to calculate the degree of dissociation at each concentration and then to examine more precisely the behaviour of soap solutions in non-aqueous solvents. The author takes this opportunity of thanking Dr. S. S. Bhatnagar for his valuable suggestions and keen interest shown throughout the whole invest igat ion. Chemical Laboratories, Benarcs Hindu Cniuemify. Renares. (India).
