TRE SYSTEN: HYDRAZINE HYDROCHLORIDE-WATER-ETHANOL
by
LAWRENCE LEE HUMPIIREYS
A THESIS
submitted to
OREGON STATE COLLEGE
in partial fulfillment of the requirements for the degree of
NASTER OP SCIENCE
June 1960 APPROVED:
Redacted for privacy Professor Chemistry In Charge of' Major
Redacted for privacy Chfrnari of Department of Chemistry
Redacted for privacy Chairman ofchoo1 Graduate Committee Redaóted for privacy
Deaí ±' Graduate School
Date thesis is presented Nay 9,. 1960
Typed by Lilah N. L otter AONOWLDGI1EN
This opportunity is taken to thank Dr. 1. C.
Gilbert for his help and. guidance throughout these investigations. TABLE OF CONTENTS
Page
INTRODUCTION...... i
EXPiRIMENTAL AND SAKLL CALCULATIONS...... 9 DIbOUSSION AND CONCLUSIONS. , ...... 21
Figure I Typical Isotherm for a Salt-Water- AicoholSystem...... 3
II Tie Line Determination ...... 6
III Graphical Determination of 1'lait
Ioint Composition...... 19
IV Isotherm for the System N2H501-
C2H5OH-H20 at 15°C ...... 23
V Isotherm for the System N211501-
C2H5OH-1120 at 25°C ...... 2k
Table I Preparation of Samples for
Soiubility Curves...... li II Composition of Saturated Solutions
of N2H5C1...... 13 III Composition of Samples on Binodai
Curve...... 1k
IV Tie Line Determination ...... 18 THE SYSTEM: HYDRA Z INE HYDROCHLORIDE-ÁATER-ETHANOL
ÏNTRODUOT ION
During a recent investigation, it was discovered that the salt hydrazine (I) hydrochloride, N2H5C1, caused an alcohol-water system to form two liquid phases at cer- tain concentrations. This is true of methanol, ethanol and propanol. The purpose of the investigations con- cerned with this paper will be to elucidate the phase diagram of the system ethanol, water, and hydrazine (I) hydrochloride at two temperatures, 15 and 25°C.
Since the beginning of the fourteenth century, when potash was used to concentrate alcohol from wine
(2), scientists have noted and studied the phenomenon now known as tsa1ting out". In 1897, systems exhibiting tis property were classified into four types of systems by
3chreineruakers (8): (a) each of the binary systems forms two liquid phases, (h) two of the binary systems form two layers, while one does not, (c) only one of the binary systems forms two liquid phases, and (d) none of the binary systems form two stable liquid phases, but the mixing of all three in certain proportions does cause separation of layers. The system wider consideration is 2 in this last group, since none of the binary systems produce two liquid phases.
Many salts, oxides, and hydroxides cause the precipitation of an organic liquid from water, but as the miscibility with water increases, the number of such compounds seenis to decrease, so that potassium carbonate has apparently been the only salt found previously which will precipitate methanol from water (14). Apparently, as the solubility of the salt in water increases compared to that in the third component, so that the preferential solubility, or distribution coefficient, for water in- creases, the saltin, out power increases.
The usual isotherm for a salt-alcohol-water system such as the one under consideration is similar to the one shown below (3).
Points a and b give the solubility of the salt in pure water and alcohol, respectively, The area o-b-d-o is a two phase area, solid salt and saturated alcohol- rich solution. The area o-a-c-o is also a two phase region, solid salt and saturated water-rich solution.
The area c-k-d-c is a two liquid phase area, and the line c-k-y is known as the binodal curve. The line x-y is a tie-line, which joins compositions of phases in equili- brium with each other. The point k is known as the 3 water
salt alcohol
Figure 1
Typical Isotherm for a Salt-Water-Alcohol System
plait-point, and is the critical point at which the tie-lines vanish, or the composition of the two phases is the sanie. The area o-c-d-o is a three phase area, solid salt and liquids of composition e and d. By the
Phase Rule, this must be an invariant area. If we ignore the vapor phase and pressure variable (a reduced system), this may be shown by
F = C-P+1 where k
C number of components = 3
P = number of phases = 3
F = degrees of freedom =
The one degree of freedom which remains has been used in holding the temperature constant. In other words, addition of any of the components will not change the composition of any of the phases until one of them dis- appears. The last area, a-x-k-y-b-alc-H20, is a region of one liquid phase, which is unsaturated.
With this background, the proposed methods for analysis of the various portions of' the curve will be discussed. The solubility curves can be determined by saturating solutions of known alcohol-water content with hydrazine hydrochloride, and then determining salt con- tent by titration for the chloride ion with silver nitrate to a dichiorofluorescin end-point.
Points on the binodal curve, c-k-d, can be ob- tamed by making up solutions of known hydrazine hydro- chloride and water content and. then titrating to in- homogeneity with ethyl alcohol. This endpoint can best be detected by means of a dye, spirit blue, which is colorless in water solutions but is a bright blue in alcohol solutìons (4). 4hen lithoinogeneity is reached 5 in the titrations, the alcohol phase appears as a bright blue ring around the top of' the water layer. If the color change is not observed, but a murkiness does appear, the line intersected is the solubility curve rather than the binodal curve.
'The tie-lines of' the binodal curve can be fixed by separating two layers in an equilibrium system for which the total composition is known. The two layers are analyzed for hyd.razine hydrochloride content by titration with silver nitrate. By intersecting the pre- viously drawn bimodal curve with a line which depicts the percentage salt, the position of the point which termin- ates the tie-line is fixed. If' this is done for both layers, and a line is drawn between the resulting points, this line must pass through the point which depicts the total composition of the system. This method is similar to that of Frankforter and Frary (k).
To locate the point known as the plait point, an adaptation was made of the Bacliman equation (1) suggested by an article of Heric (5). The equation has been applied chiefly to ternary systems of liquids of' which two are immiscible. By using ethanol and hyclrazine hydrochloride as the "immiscible'7 pair, it is believed that the method can be successfully applied to the water layer rye
omposition
alt in alcohol layer
alcohol
Figure 2
Tie-Line Determination
present investigation.
The tie lines of a ternary system which exhibits two liquid phases are very rarely parallel, so that the interpolation of known tie line data is difficult and. often unsatisfactory. flany attempts have been made to correlate tie lines, one of which is the Bachrnan equation (7). This equation, which relates the ratio of the major non-consolute components to the composition of one of the phases, is expressed empirically by
(x)(y) = ax + by 7 where A and B are non-consolute components. Here, x is
the weight percentage of A in the A-rich layer, y is the weight percentage of' B in the B-rich layer, and a and b are empirical constants for a given isotherm. This equation may be rewritten in the form
x = a(x/y)+b
By plotting x versus x/y, a straight line results which correlates the tie line data. By picking a value of x from this line, the value of y which must be in equili- briwn with it can be found. This line must pass tbrough the plait point. If now another straight line is estab- lished from points of the binodal curve plotted in the same manner as above, this latter line must represent the locus of points somewhere upon which the plait point must lie. The intersection of these two lines then gives the location of the plait point. This method works very well for this liquid-solid system by taking ethanol and hydrazine hydrochloride as the non-consolute pair.
The area under the binodal curve, and the plait point, are dependent upon the temperature. Tinuiierans
(10) stated that all systems have an upper and a lower critical temperature. In this range, the two liquid phases may be formed at certain concentrations. Outside ri L'-J of this range, however, the two liquid phases cannot be formed. The critical temperatures cannot always be realized experimentally, due to the fact that they may lie above the boiling point or below the freezing point of a liquid component. Usually, however, at least one of the critical temperatures can. be found. EXIiR flLNTAL
The hydrazine (I) hydrochloride used was prepared by the reaction of liquid hydrazine with chemically pure hydrochloric acid. The reaction proceeds according to
the following equation;
N2H4 + HOl -. N2115C1
The hydrazine was placed in a beaker in an ice-bath.
The hydrochloric acid was added to the reaction vessel drop by drop from a self-filling burette with constant stirring. The time for addition of acid was about three hours. The end-point for the reaction is the neutral color of methyl orange indicator, because if the solution is more acidic than this, sorne dihydrochioride forms.
The reaction mixture was evaporated until crystals formed and was then crystallized from 80% methanol. The preci- pitate was collected on a sintered glass filter with suction and was then dried at 60°C and. 20 mm pressure over calcium chloride for several days.
The refractive index of the ethanol used was found to be 1.3592 for the sodium line at 25°C, which agrees very well with the accepted value of 1.3594 for absolute ethanol at this temperature (6). Hydrazine hydrochloride content of the solution
was determined by titrating for the chloride ion with
silver nitrate. The procedure is outlined in the fol-
lowing steps: (a) add two or three drops of dichioro-
fluorescin to the sample as indicator, (b) add one or
two cc of chloride free dextrine solution, (c) color
changes from green to orange and precipitate coagulates
at the end-point, (d) the solution must be neutral. Two
silver nitrate solutions were prepared, the concentra-
tions of which were O.05N and O.50N. These were stan- dardized with sodium chloride and then against dried hydrazine hydrochloride. The two titretions agreed within one-tenth of one percent.
The temperature was controlled by means of a water-bath with a thermostat. At 25°, the temperature was constant within plus or minus five-hundredths of a degree, but at 15° it varied about one-half of one degree in either direction, All samples were given at least 1+8 hours rotation in the water-bath to reach equilibrium. The titrations for points on the binodal curve, where turbidity was the end-point, were carried out in the water-bath, and considerable time was needed for the system to reach equilibrium after the addition of alcohol. In fact, the system was relatively slow in 1].
attaining any equilibrium.
To find points on the solubility curve, (lines
a-c and. b-d), samples of the following ethanol-water ratios were prepared and then saturated with hydrazine hydrochloride at 25°C. All percentages given in tables
or calcuLtions are on a weight basis.
Table I. Preparation of sa:nples for solubility curves
sample number 1 2 3 5 6 percent water loo 95 90 10 5 0 percent ethanol O 5 10 90 95 100
The total weight of ethanol and water present in the sample may be found by subtracting weight N2H5C1 from sample weight. The individual weights may then be found from the initial percentages of ethanol and water, which gives the weight ratio present. This is done in the sample calculation be1oi.
Sample Calculation of Point on Solubility Curve - sample 2
weight sample plus bottle...... 66.198
weight bottle...... s . . e 64.0308
weightsample...... 2.3890
final burette reading...... 43.33
initial burette reading...... 0.35 ml AgNO3 ...... '4-2.98
normality ÂgI03...... 0.5002
milliequivalents LtgNC3 ...... 21.49
weight I9i01...... 1.471
weight ethanol plus water...... 0.918
fraction ethanol ...... 0.05
weight ethanol ...... 0.046
weight water ...... 0.872
percentN2H5Cl ...... 61.6
percent water...... 36.5 percentethanol...... 1.9
Points on the binodal curve, line c-k-d, were obtained by weighing a flask, transferring some N2H5C1 to the flask, weighing again, adding water and weighing again. The solutions were then titrated to inhomogeneity with ethanol and weighed again.
Sample Calculation of Point on Binodal Curve - sample 3
weight bottle plus C2H5011, N2H501, andwater...... 33.5225 weight bottle plus water and N2H501. 32.8558
weight ethanol ...... 0.6667
weight bottle plus salt...... 30.8530
weightwater...... 2.0028 Table II-A. Composition of saturated solutions of N2115C1 at 15°C
samplenuinber 1 2 3 4 5 6 7 8 percent N2H5C1 56.8 54.1 50.0 47.2 45.5 0.81 0.43 0.24
percent water 43.2 43.5 45.0 44.9 43.4 9.93 4.98 0 percent ethanol 0 2.3 5.0 7.9 11.1 89.26 94.59 99.76
Table II-B. Composition of saturated solutions of N2115C1 at 25°C
sample number 1 2 3 4 5 6 percent N2H5C1 64.4 61.6 58.6 1.25 0.61 0.32
percent water 35.6 36.5 37.3 9.87 4.90 0 percent ethanol 0 1.9 4.1 88.88 94.49 99.68
I-J 1k
weight bottle ...... 29.2287
weightsalt...... l.62k3
total weight...... k.2938
percent salt...... 37.8
percentwater...... k6.6
percent ethanol ...... 15.6
Table III-Â. Composition of Samples on Binodal Curve at 15°C
sample number % water % N1i5C1 % ethanol
i k3.9 k4.3 11.8 2 3k.1 11.2 54.7 3 25.6 ik.5 67.9 k 38.7 16.7 '44.6 5 46.3 33.1 20.6
6. 17.2 3.0 79.8 7 41.2 20.6 38.2 8 45.6 37.3 17.1 9 '44.0 26.9 29.1 10 31.7 9.5 58.8 11 42.3 22.8 34.9 15
Table IIIBe Composition of Samples on Binodal Curve at 25°C
sample number % water % NH5C1 % ethanol
1 41.5 51.2 7.3 2 45.1 45.3 9.6
3 46.6 37.8 15.6
'4- 37.4 57.7 4.9 5 45.2 30.1 24.7 6 20.0 4.6 75.4 7 42.2 22.8 35.0 8 35.2 13.6 51.2 9 28.8 9.0 62.2 10 44.7 28.7 26.6 11 25.5 4.5 70.0 12 18.6 3.7 77.7 13 38.8 17.7 43.5 14 31.6 10.3 58.1 15 14.2 2.5 83.3 16 41.5 22.0 36.5 17 0.3 0.3 99.4 18 11.4 1.8 86.8 19 22.3 3.6 74.1 20 35.6 13.6 50.8
The information obtained from these titrations gave a plot of the curve, but there was no distinguish- able break between the binodal curve and the solubility curve on the alcohol-rich side (point a). The point of intersection of the curves could not be obtained by the 16 previous titration method, because the change was not discernable. A saturated two liquid phase system was analyzed for hydrazine hydrochloride content in the alcohol layer. The point on the previously drawn curve which had this same salt content was the termination of the binodal curve.
Calculation of % N2H5C1 in Saturated Alcohol Layer
weight bottle plus sample. . . . . 60.k814
weight bottle...... 51.5968
weight sample...... 8.8864
final burette reaalng...... 21.00
initial burette reading...... 6.72
milliliters AgNO3...... 14.28
normality .gNO3...... 0.5002
milliequivalents AgNO3 ...... 7.14
weight N2115C1...... 0.489
percent N2H5C1 ...... 5.51
The value obtained for hydrazine hydroeliloride in the saturated alcohol layer at 15°C was l.6%, and that for the water layer was 43.8%. The compositions of these saturated layers give the junction of the binodal curve with the solubility curve.
Tie-lines were determined by preparing a solution 17 whose total composition was inside the binodal curve.
The system was allowed to equilibrate in the water-bath, and then the two phases were separated. The phases were analyzed for hydrazine hydrochloride content, and this value gives the termination point of the tie-line on each side of the binodal curve (points x and y). The method for determination of hydrazine hydrochloride con- tent in the two layers was exactly the saine as that given above for the saturated layers. The values obtained and. total compositions are given in Table IV.
Plait-Point Determination
Using Bachnan Equation (see introduction)
X = a(x/y)+b
X % N2H501 in water layer
y = % C2H5OH in alcohol layer
when x = 51, y = 69, and x/y = 0.7k
51 = 0.7k) + b (1)
when x = 47, y = 65, and x/y = 0.724
47 = a(Q.724) + b (2)
By simultaneous solution of equations (1) and (2)
a = 250
b = -134
Bachman quation at 25°C for this system
x = 250(x/y) - 13k Table IV-A. Tie-line Determination at 15°C
percent N sample total composition 211501 number % H0 % 02115011 % N2H501 ff20 layer aic. layer
i 43 30 27 38.6 23.0 2 LI3 27 30 40.5 18.9
Table IV-B. Tie-line Determination at 25°C
sample total composition percent N2115C1 number % 1120 % C2H5OH % NH5Cl 1120 layer alc. layer
1 37.0 43.0 20.0 41.0 14.65 2 33.0 45.0 22.0 46.9 8.28 3 35.0 30.0 35.0 51.2 7.48 19
Possible plait-points from binodal curve
x 22 20 25 27
y 37 39.5 31 29
x/y 0.60 0.51 0.81 0.93
Por plot of data see Figure III
X/ y
LO - -Z.____ points from / binodal curve
6
plait-point 4 plot o f composition Bachman Equation x = 22 2 x/y = 0.620 y = 35.5 /i I i i i i IO 20 30 40 50 60 70
%N2k5CI in water
Figure III. Graphical Determination of Plait-point Composition
This same procedure was used to determine the composition
of the plait-point at 15°C, and it was found to be 32% 2H5C1, 22 alcohol, and 46% water.
An attempt was made to determine the lower
critical temperature by preparing a sample just inside 20 the binodal curve. The sample composition was 45% water, 30% salt, and 25% alcohol. The temperature was lowered to 0°C but the two liquid phases remained. The sample was at this temperature for 60 minutes, so that temperature equilibrium could be reached. The critical temperature apparently lies below the freezing point of the solvent. 21
DISCUSSION AND CONCLUSIONS
The purpose of this investigation was to determine
the isotherms of the system hydrazine (I) hydrochloride, water, and ethanol at temperatures of 15 and 25°C. These
isotherins have been elucidated and are given in Figures
IV and V.
The ten-degree change in temperature produced a considerable change in the solubility of the hydrochloride in water, while its solubility in ethanol remained essen- tially uiichanged, The area of two liquid phases decreased considerably between the two isotberms, which was ex- pected, due to the relative decrease in water solubility of the salt.
Below is a discussion of the problems encountered and the value of the methods used in the investigation.
I - All crucial values were the averages of six determinations, and all other determinations were in tri- plicate. The following six values were obtained from re- peated titrations of a sample on the water-rich solubility curve: 36.6, 36.5, 36.3, 36.5, 36.5, 36.5 percent water.
These values yield an average deviation of O.W/o. The average deviation of all determinations made did not ex- ceed 0.3%. The points on the binodal curve are individual values, which were run three at a time. All of these 22
points fell on a smooth curve but no effort was made to
duplicate each point because of the nature of the ti-
trations (page 12). The various proportions of' water
and hydrazine hydrochloride gave each of the samples a
separate point of intersection with the binodal curve.
II - The method of plait-point determination was
applied as a result of an article which recently ap-
peared in the literature. The location of the plait-
point at 25° agrees with the e)c$)ectei value, but the
value calculated for the 15° isotherm is not quite that
expected. The points plotted for the lower temperature
do not fall on a straight line, but rather show a slight
trend toward curvature. The success of the method is,
therefore, still not completely demonstrated, though
apparently it has merit.
III - The temperature at which the binodal curve disappears in thLs system could not be determined by casual observation. This is presumably due to the fact that the temperature is below zero or possibly to slow- ness in attaining equilibrium (see Coiclusions V).
IV - The junctions of the binodal curve and the solubility curves could have been determined by ultimate analysis for water and ethanol. However, the author felt that this method represented a larger source of error (by 00% H20
H5OH
N2H5C I '00% o
FIG. 4 Isotherm of the system NH5CI -C2H5OH-H20 ut 15° G. (M 00% H20
50H
N2H5C I 00% ro FIG. 5 Isotherm of the system N2H5CI-C2H5OHr-H20 at 25°C. 25
virtue of the multiple transfers involved) than the method employed (page 15).
V - The major problem encountered during these
investigations was that of the time required for the
establishment of complete equilibrium -- some samples required as much as five days to completely reach equi-
librium between all phases. 26
BIBLIOGRAPHY
1. Bachxnan, I. Tie lines in ternary liquid systems. Industrial and Engineering Chemistry. Analytical Edition 12:38-39. 1940.
2. DeBruyn, B. A summation of the knowledge of the equilibria between two liquid phases in a system of an alkali salt, water, and alcohol. Zeitschrift fur Physikalische Chemie 32:63-114. 1900.
3. Findlay, Alexander. The Phase Rule. 9th ed. New York, Dover Publications, Inc., 1951. 384 p.
4. Frankforter, G. B. and Prary, E. C. Equilibria in systems containing alcohols, salts, and water, in- cluding a new method of alcohol analysis. Journal of Physical Chemistry 17:402-473. 1913.
5. Heric, L. L. Tie line correlation and plait point determinations. Journal of Chemical Education 37: 144-145. 1960.
6. International Critical Tables. V. 7. New York, NcGraw-Hi11, 1930. p. 67.
7. Othnìer, D. F. and P. E. Tobias. Tie line corre- lation. Industrial and Engineering Chemistry 34: 693-700. 1942.
8. Schreinemakers, F. k. H. Concerning the equilibria in a system of three components, from which two liquid phases result. Zeitschrift fur Physikalische Chemie 23:649-666. 1897.
9. Smith, J. C. Solubility diagrams for ternary and quaternary systems. Industrial and Engineering Chemistry 41:2932-2935. 1949.
10. Tiinmerans, J. The critical solution temperatures of ternary systems. Zeitschrift fur Physikalische Chemie 58:129-139. 1907.