in the System

to purge the sampling line to receivers &, and a Dortion of this. Figure 4. ... first receiver Q to be retained for analy- ..... (18) McIntosh, J. Phy...
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Phase Equilibria

The phase equilibrium relations of the sthane-ethyleneacetylene system has been studied at two temperatures, 40" and 60' F., and at a series of pressures in 50-pound intervals covering the entire two-phase region at each temperature. The constant-boiling mixtures of the ethaneacetylene and ethylene-acetylene systems persist through the triangular three-component diagrams. A t constant temperature and pressure these diagrams have two two-phase areas. Acetylene is the most volatile constituent in one area and the least volatile in the other area.

in the System

ETHANEIETHYLENE-ACETYLE J. LLOYD McCURDY'

I

N STUDIES of hydrocarbon phase behavior, binary mixtures of acetylene and ethane ( I S ) and acetylene and ethylene (6) have been shown to form constant-boiling mixtures under pressure. Since mixtures of these gases result from high-temperature cracking processes and are present in hydrocarbon mixtures during separation, the vaporization characteristics are of particular interest. Acetylene has been found to have vaporization tendencies differing from those which would be predicted by the position of its vapor pressure curve as related to the vapor p r e s sure curves of other hydrocarbons. The next step from binary systems in studying the behavior of acetylene as related to complex mixtures is the use of ternary systems in which the effect of temperature, pressure, and composition may be studied. This procedure has been followed for other ternary systems such as the methane-propane-pentane (5, 9) and methane-ethane-ethylene (11) systems, but these systems were composed of components which in the binary state did not form constant boiling mixtures but gave normal vaporization 1

AND DONALD

L. KATZ

University of Michigan, Ann Arbor, Mich. characteristics. The ethane-ethylene-acetylene ternary system was chosen for study since two of the binary systems are known to form constant-boiling mixtures, and the third, ethane-ethylene, has been shown to be of the normal type (21). Vapor and liquid compositions were determined for mixtures of these three components in the two-phase region at 40' and a t 60' F. a t 50-pound pressure intervals throughout the two-phase region. At these temperatures ternary mixtures of these three components have two two-phase regions. It was found that acetylene is more volatile in one of these t w o - p h w regions and is the least volatile in the other; this fact stresses the importance of the composition of the mixture on equilibria at any temperature and pressure. The experimental data, along with those available in the literature on normal systems, form a pettern for the prediction of the behavior of ternary systems when the behavior of the bihary systems for the three components is known. The properties of the pure components ethane, ethylene, and acetylene have been studied extensively. The vapor pressures of the pure components are presented in Figure 1 (4, 8, 14-30). The acetylene and ethane curves cross at approximately -40' F. Acetylene has both the highest critical temperature and the highest critical pressure. The critical loci of the binary mixtures of the three pairs of components are the curves connecting the critical points. The critical locus for the ethane-ethylene system

Ptesent address, California Research Corpoxation, Richmond, Calif.

-

T E M P E RA T u RE OF.

Figure 2. Figure 1. Vapor Pressure of Pure Components 674

Acetylene-Ethane Binary System after Kuenen (14)

July, 1944

INDUSTRIAL AND ENGINEERING CHEMISTRY

675

METHODS AND APPARATUS

The a paratus was composed of purification systems, equilibrium Celt and gas analysis ap aratus. The equilibrium cell had a volume of 92 cc. and had Auble glass windows for observing the condition of the sample within the cell. Figure 3 shows the cell A, enclosed in a constant-temperature air bath, K , cooled b brine coils X and heated by heater X. Mercury was used as t l e conhing fluid. The temperature of the cell was measured by a double-junction copper-constantan thermocouple embedded in the wall of the cell and a mercury-in-glass thermometer. A thermoregulator ave temperature control to +0.1 F. Pressure was measured w i b a calibrated Bpurdon-tube pressure gage with 10-pound scale divisions and with estimations to the closest pound. The apparatus was supported on axis P R and was rocked to agitate the fluid phases and thus bring them into equilibrium. It was necessary to adjust the com osition so that two phases could be obtained, since the two-pgase region for the two comr t s is relatively narrow at 40" and 60" F. .After being rocked or 15 minutes, the cell was placed in a vertical position ready for sampling the e-quilibrium phases thrqugh valve C. Mercury in cylinder M driven b compressed nitrogen, was allowed to enter the equiibrium celrthrough valve D a t the same rate that gas phase was aIlowed to leave the cell. The gas phase was used to purge the sampling line to receivers &, and a Dortion of this O

Figure 3. Diagram of Apparatus

e

is a smooth curve connecting the two critical pgints, whereas the critical loci for the other two binary systems exhibit minimum points with respect to temperature. These minimum temperature points are associated with binary systems which form constantboiling mixtures. One of the earliest systems showing that hydrocarbons may form constant-boiling mixtures is the ethane-acetylene system, investigated by Kuenen (14). Figure 2 shows the critical locus and the border curve for the 68 mole % ' ethane mixture as presented by Kuenen. The two-phase region is not bounded by the vapor pressure curves of the two constituents for mixtures of this type, and two phases may exist for ethane-acetylene mixtures a t pressures above the vapor pressure of the most volatile constituent. The volatility of aseotropic mixtures therefoce, may not be predicted from the position of the vapor pressure curves of the pure constituents. Kuenen's data are of little use for quantitative vaporization calcu!ations because of impurities which apparently entered the system. The dotted curve of Figure 2 is the revised position of the c?tical locus and minimum temperature curves as obtained from this research. Acetylene is an endothermic compound rtnd has been the source of several explosions when in the pure state under pressure. Acetylene is transported in cylinders containing a porous solid and acetone to decrease the possibility of explosion (7). If acetylene is suddenly decomposed in a closed vessel, the heat of decomposition causes the pressure to rise ten or eleven fold, according to the size of the container (1,82), Apparently the conditions for decomposition of pure wetylene are unpredictable, as judged by miscellaneous reports in the literature (9, 5, 10, 12, 24, 26). It is evident, however that up to pressures of 25 pounds per square inch absolute, acetylene in the pure state is relatively safe. At pressures of 400 pounds per square inch upward, pure acetylene is not safe unless i t is in a porous medium or is diluted with some other material such as another hydrocarbon; even then extreme caution should be exercised. The presence of gas oil in acetylene mixtures at pressures up to 20 atmospheres has been shown to reduce the tendency for acetylene to decompose (28,26). Acetylene is known to form metallic acetylides which are very unstable, especially when dry (10). These acetylides serve as a convenient basis for the analytical determination of acetylene. Notable among them are copper, silver, and mercury acetylides.

Figure 4.

Ethane-Ethylene-Acetylene A.

Phase Equilibria

764 lb. per a q in. abs., 60* F.

B . 514 lb. per eq:'!n. abs., 40D F. C. 564 ib. per sq. in., 40' F.

I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY

676

phase was permitted t o displace the mercury in the E' first receiver Q to be 0 80 retained for analyv) tical purposes. As a the meniscus beE tween the vapor Vi 70 and liquid ap-I proached the top of I the equilibrium cell, Y vapor phase wa8 no f 76 longer sampled; but the meniscus z and a portion of the E l i q u i d were dis74 Dlaced from the cell 52 54 56 58 60 TEMPERATURE' OF. hntil t h e ,liquid phase had purged Ftgure 5. Pressure-Temperature the sample 1i n e , Diagram for 0.46 Acetylene-0.54 and then a Ethylene of the liuuid phase which had vaporized upon the reduction in pressure to atmospheric was collected in the second sampling tube &. Ordinary gas absorption methods were used for determining the concentrations of acetylene and ethylene in phase samples. Approximately 100 cc. of the gas at atmospheric pressure were measured in a buret, using mercury as the confining fluid with a covering layer of 12.5% sodium sulfate-Z.6yo sulfuric acid solution. The gas was passed through a pipet containing potassium iodomercurate solution which absorbed the acetylene. It was found that some ethylene was also absorbed and calibration was necessary, especially for fresh solutions. Whenever three passes through the potassium iodomercurate solution (lasting one minute each) did not cause a reduction in the volume of the sample by more than 0.1 cc., the acetylene wag considered to be removed. The ethylene was removed by a bromine water pipet, followed by passage through p o t a s s i u m hydroxide solution to remove any bromine vapor entering the sample. The ethane could be observed by d i f f e r e n c e , but on several occasions the ethane was burned with oxygen and combufition analysis was used to prove that the remainder was ethane. V J

82

6

purity was given a8 97.6% ethane, the remainder being principally ethylene with small amounts of propane and heavier. A purification system was set up to remove the propane and heavier constituents by partial condensation at low temperature and cylinder pressure. The concentrated propane and heavier fraotion was discarded. No attempt was made to remove the ethylene present since its presence was not objectionable. The acetylene wm obtained from an ordinary Prest-0-Lite welding cylinder. Analysis showed a purity of 97.5% acetylene with 2.44% nitrogen, 0.05% oxygen, 0.01% carbon monoxide. Acetylene wm also purified by liquefaction with a dry ice-acetone bath around a container which had been packed with asbestos. A portion of the liquefied material was exhausted so as to remove noncondensed nitrogen, carbon monoxide, and oxygen, and leave relatively pure acetylene. The noncondensable gases vented were approximately ten times the volume of the nitrogen, oxygen, and carbon monoxide present in the sample, and should have left quite pure acetylene. Each time the equilibrium cell was charged with a hydrocarbon mixture, a new batch of acetylene was prepared. I n ail cases ethane was placed in the equilibrium cell before acetylene was admitted, to ensure that pure acetylene would not be present under high pressure in a container which did not contain a porous solid or diluent. I n order to admit acetylene to the equilibrium cell, the liquefaction cell was separated from the Prest-0-Lite cylinder and the cooling medium removed. The acetylene pressure could, therefore, be controlled by the temperature rise of the liquefaction cell, and acetylene could be added to the equilibrium vessel when the pressure was sufficiently high.

MATERIALS

Ethylene was purc h a s e d f r o m Ohio Chemical & Manufacturing Company with a guaranteed p u r i t y of 99.5% ethylene. Analysis showed a purity of 99.5 to 99.8% ethylene, and i t was used d i r e c t l y from the high-pressure cylinder. Ethane had been supplied by C a r b i d e & Carbon Chemicals Corporation for previous research ($7). The

MOL FRACTION ACETYLENE

Figure 6.

Vol. 36, No. 7

Summarized Binary and Ternary Diagram at 40' F.

July, 1944

INDUSTRIAL AND ENGINEERING CHEMISTRY

677

RESULTS

The experimental measurements covered t h e entire pressure range at which two phases can exist at 40' and 60" F. The point 40" F. is below the critical temperature of all three pure constituents, whereas 60' is below the critical temperature of ethane and acetylene but above that for ethylene. The compositions of the V* por and liquid phases were determined for each temperature and pressure and at a series of cell compositions of varying proportions of the three constituents. Duplicate or triplicate analyses were made on each phase to assure a m i n i m u m of e r r o r . Table I gives the original data for the four pressures investigated a t 40" F. and for the five pressures investigated at 60" F. These values were plotted on triangular coordinates; Figure 4 shows t h e t y p e s of d i a g r a m s resulting. Figure 7. Summarized Binary and Ternary Diagram at 60" F. Some smoothing of the data was necessary in order to plot the curve through the bubble and dew point made for five other mixtures as described in Table 111. The revalues determined a t the several compositions. A plot was made sults of these phase diagrams were primarily to estimate the critical locus for the 60" F. investigation. I n addition, they serve as of mole fraction acetylene in the vapor and mole fraction acetylene in the liquid; with this the slope of the tie lines connectan independent check upon the vapor-liquid compositions given

vapor and liquid compositions at fairly eve

the binary phase diagrams at opposite the side of the ternary nary system. The pressure inhat diagram gives the border t curves for the ternary dia-

control and observation probably were within ~3 pounds per square inch of the true value, and in some cases this tolerance permitted relatively large changes in the phase composition. The analytical method gave results differing by not more than 0.2%, based upon the entire sample, but with increasing percentages for the concentration of the individual constituents. of vapor and measurements liquid phases, pressure, volume, ion, memixwere made on specific mixtures of known 0 ture was maintained in the equili border curves for bubble and dew points were de as well as by the percentages of va extremities. Figure 5 shows such a diagram for the 54 mole % ethylene-46 mole % acetylene mixture. Similar diagr were

diagram intersects the bubble and dew and forms two two-phase regions a t the

the azeotropic mixture of ethylene and acetylene. Further, the bubble and dew point lines become tangent a t each pressure as they cross the azeotropic locus, and the tie lines at these points have a length of zero, i.e.7 the equilibrium constants of the three components of ternary mixtures along the azeotropic locus are all unity. s represented along this locus sition along this line were vaporized, the vapor would have the same composition as the liquid and thus give the impression of a pure compound.

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TABLEI. ORIGINAL DATAAT 40' Pressure Lb./Sq. Ih. Abs. 464.4 514.4

564.4

614.4

664.4

614.4

AND

60"F.

Mole Fraotions (Liquid) Mole Fractions (Vapor) EthylAcetyEthylAcetyene ene Ethane lene lene Ethane Data a t 40° F. 0,017 0.853 0.130 0.013 0.788 0.199 0.244 0.754 0.002 0.304 0.692 0.004 0.156 0.791 0.053 0.187 0.731 0.082 0.697 0.015 0.015 0.288 0.630 0.355 0.595 0.368 0.421 0.037 0.526 0.053 0.243 0.638 0.119 0.279 0.565 0.156 0.192 0.150 0.658 0.590 0.168 0.242 0,010 0.176 0.814 0.010 0.232 0.758 0.075 0.082 0.114 0.108 0.843 0.778 0.128 0.013 0.190 0.014 0.859 0.796 0.532 0.426 0.042 0.587 0.363 0.050 0.158 0.446 0.175 0.396 0.416 0.408 0.250 0.493 0.411 0.257 0.273 0.286 0.484 0.361 0.155 0.887 0.427 0.188 0.126 0.427 0.447 0.138 0.407 0.455 0.167 0.452 0.381 0.181 0.420 0.399 0.131 0.239 0.150 0.260 0.630 0.590 0.141 0.226 0.633 0.159 0.250 0.591 0.276 0,012 0.712 0.332 0.014 0.653 0.185 0.157 0.658 0.190 0.199 0.611 0.274 0.016 0.710 0.336 0.019 0.645 0.165 0.181 0.193 0.202 0.654 0.605 0.119 0.328 0,553 0.129 0.335 0.536 0.677 0.247 0.692 0.219 0.076 0.089 0,785 0.215 0.189 0 0.811 0 0.250 0.623 0.127 0.635 0.223 0.142 0.216 0 503 0 281 0.517 0,199 0.284 0 I202 0.482 0.316 0.602 0.188 0.310 0,202 0.497 0.301 0.516 0.186 0.298 0.041 0.459 0.500 0.493 0.047 0.460 0.132 0.440 0.428 0.130 0.465 0.405 0.067 0.829 0.104 0.836 0.061 0.103 0.032 0.745 0.224 0.751 0.032 0.217 0.047 0.923 0.030 0.040 0.925 0.035 0.745 0.024 0.231 0.755 0.022 0.223 0.030 0.950 0.020 0.950 0.025 0.025 Data at 60' F. 0.694 0.306 0 0.358 0.642 0 0.704 0.296 0 0.352 0.648 0 0.367 0.633 0 0:741 0:226 0 033 0.264 0.673 0.063 0.674 0.816 0.010 0.347 0.637 0.016 0.783 0.106 0.111 0.132 0.720 0.148 0,785 0.105 0.110 0.119 0.737 0.144 0.819 0.033 0,148 0.770 0.038 0.192 0.752 0.205 0.043 0.707 0.223 0.070 0.837 0.010 0.153 0.785 0.014 0.201 0.707 0.265 0.028 0.299 0.662 0.039 0.752 0.206 0.042 0.231 0.703 0.066 0.741 0.193 0.066 0.218 0.688 0.094 0.757 0.173 0.070 0.146 0.709 0.096 0.586 0.345 0.069 0.542 0.374 0.084 0.684 0.031 0.285 0.033 0.647 0.320 0.130 0.666 0.214 0.163 0.588 0.249 0.576 0.355 0.533 0.069 0.387 0.080 0.114 0.609 0.277 0:&7 0:264 0 : iig 0,541 0.310 0.149 0.122 0.069 0.809 0.077 0.138 0.785 0.166 0,018 0.816 0.021 0.204 0.775 0.126 0.034 0.840 o:i8s o:oiz 0.840 0.147 0.013 0:802 0.583 0.406 0.011 0.610 0,375 0.015 0.435 0.4W 0.076 0.511 0.405 0.084 0.448 0.427 0.423 0.125 0.444 0.133 0.477 0.231 0.292 0.247 0.448 0.305 0 0.224 0.776 0 0.278 0.722 0.472 0.351 0.177 0.451 0.360 0.189 0.102 0.195 0.703 0.118 0.224 0.660 0.261 0.47b 0.260 0.269 0.449 0.282 0.442 0.447 0.111 0.417 0.481 0.122 0.215 0.164 0.621 0.226 0,181 0.592 0.067 0,211 0.722 0.248 0.070 0.682 0.174 0.393 0.433 0.380 0.178 0.442 0.154 0.180 0.666 0,165 0.196 0.689 0.185 0.172 0.643 0.198 0.187 0.615 0.311 0.185 0.524 0.175 0.308 0.517 0.454 0.215 0.331 0.437 0.208 0.355 0.323 0.156 0.521 0.154 0.328 0 518 0.105 0.407 0.487 0,112 0.394 0.494 0.023 0.416 0.562 0.026 0.443 0.531 0.282 0.375 0.343 0.277 0.384 0.339 0.385 0.149 0.466 0.404 0.149 0,447 0.151 0.377 0.472 0.390 0.155 0.455 0,285 0.505 0.210 0.508 0.277 0.215

TABLE 11. SMOOTHEDEQUILIBRIUM VAPOR COMPOSITIONS pressure Lb./Sq. Ih. Abs. 464

514

564

614

:

664.4

714.4

764.4

664

614

664

714

Acetylene 0.063 0.094 0.161

...

0:iio

Ethane 0.302 0.281 0.269 0.440 0.285

...

I

Critioal Temp., O F. 59.4 59.2 59.4 66.8 62.0 60.0

Critical Pressure. Lb./Sq. In. Abs.

764.4 763 4 772.4 752.4 754.4 822.4

I

764

AND

LIQUID

Mole Fractions (Vapor) Mole Fractions (Liquid) AoetyEthylAoetyEthyllene ene Ethane lene ene Ethane Data at 40' F. 0.306 0.694 0 0,250 0.750 0 0,299 0.695 0,004 0.244 0.752 0.006 0.186 0,731 0.054 0.156 0.790 0,083 0.016 0.784 0,132 0,016 0.852 0,200 0 0.789 0.141 0 0.859 0.211 0 0.419 0.581 0.489 0,511 0 0.419 0.528 0.037 0.367 0.596 0.053 0.279 0,563 0.120 0.248 0.582 0.158 0.168 0.590 0,190 0.149 0.661 0.242 0.016 0,628 0.284 0.015 0.701 0.356 0.706 0,294 0 0 0.632 0.368 0 0.180 0,243 0.820 0 757 0 0.167 0.823 0.010 0,230 0,010 0.760 0.085 0.840 0.075 0.108 0.113 0.779 0.014 0.356 0.130 0.189 0.016 0.795 0 0.859 0.141 0 0,201 0.799 0.590 0.401 0 0.660 0.340 0 0.535 0.423 0.363 0.042 0.050 0.586 0.362 0.484 0.425 0.154 0.390 0.185 0.250 0.496 0,254 0.440 0.284 0.276 0.453 0.381 0.166 0.181 0.421 0.398 0.158 0.446 0..4'19 0,394 0.406 0.175 0.130 0.422 0.448 0.406 0.456 0.138 0.388 0,493 0.119 0.388 0.493 0.119 0.118 0.327 0,555 0,127 0,333 0.540 0.134 0.240 0.626 0.261 0,589 0.150 0.140 0.220 0.640 0.158 0.250 0.592 0.159 0.186 0,655 0,192 0.200 0.608 0.162 0.183 0.656 0,193 0,196 0.609 0.275 0.016 0.709 0.017 0.333 0.650 0.651 0.335 0.014 0.710 0.277 0.013 0.287 0 0.713 0 0,346 0.654 0.784 0.216 0 0,820 0.180 0 0.778 0.217 0.005 0.801 0.189 0.010 0.678 0.245 0.219 0.077 0,690 0.091 0,625 0.251 0.124 0.632 0.226 0.142 0.508 0.210 0,197 0.282 0,518 0.285 0.497 0.203 0,300 0.193 0.508 0.299 0.489 0.197 0.314 0.189 0.499 0.311 0,465 0.170 0,365 0.465 0,170 0.365 0.445 0.132 0,130 0,423 0.465 0.405 0.460 0.042 0.498 0,044 0.496 0.460 0.475 0 0.525 0 0.519 0.481 0.991 0 0.009 0 0.987 0.013 0.953 0.026 0.021 0.951 0.023 0.026 0.926 0.045 0.029 0,040 0.926 0.034 0.829 0,068 0.103 0.060 0,834 0.104 0.759 0.051 0,190 0.759 0,051 0,190 0.746 0.031 0.223 0.031 0,753 0.216 0.023 0,230 0.747 0.022 0.755 0.223 0.751 0 0.249 0.763 0 0.237 Data at 60' F. 0.694 0.306 0 0.641 0 0.359 0.714 0.264 0.022 0.667 0.297 0.036 0.730 0.223 0.042 0.687 0.254 0.061 0.738 0.212 0,692 0.060 0.237 0.071 0.740 0,209 0.051 0.697 0.228 0.075 0.749 0.189 0.062 0.705 0.209 0.086 0.756 0.174 0.710 0.070 0.195 0,095 0.789 0.102 0.741 0.109 0.122 0.137 0.789 0.102 0.109 0.745 0.116 0 140 0.820 0.033 0.147 0.780 0.034 0.186 0,832 0.011 0.157 0.789 0.198 0.013 0.838 0 0.162 0.795 0.205 0 0.555 0.445 0 0.503 0.497 0 0,583 0.351 0.066 0.533 0.387 0,080 0.583 0.350 0.067 0,539 0,376 0 085 0.610 0.263 0.127 0.562 0.297 0.141 0.652 0.133 0.215 0.603 0.157 0.240 0,684 0.035 0.640 0,281 0.036 0.324 0.696 0 0.304 0.650 0 0.350 0 0.147 0.853 0 0.193 0.807 0.013 0.137 0.850 0.014 0.804 0.132 0.110 0.062 0.828 0.138 0.785 0.079 0.166 0.019 0.815 0.206 0.773 0.021 0.190 0 0.230 0.810 0 0.770 0.400 0,600 0 0.365 0.635 0 0.405 0.583 0 IO12 0,373 0.612 0.015 0.430 0.494 0.076 0.402 0.511 0.087 0.445 0.445 0.110 0.418 0,122 0.460 0,450 0.427 0.123 0.423 0.444 0.133 0.471 0.352 0.177 0.447 0.363 0.190 0.480 0.262 0.258 0.454 0.268 0.278 0,234 0.473 0.293 0.450 0,246 0,304 0.460 0.212 0.328 0.434 0.210 0.356 0.360 0.156 0.474 0.360 0.156 0.474 0.215 0.165 0.620 0.224 0.182 0.594 0.185 0.173 0.642 0.201 0.190 0.609 0.154 0.181 0.665 0.166 0.203 0,631 0.130 0.199 0.698 0.115 0.225 0.660 0.063 0.214 0.723 0 069 0.247 0.684 0 0,240 0,760 0 0.280 0.720 0.162 0.570 0.268 0.162 0 570 0.268 0.214 0.508 0.278 0,210 0.504 0.286 0.393 0,362 0.245 0.393 0.362 0.245 0 455 0.391 0.154 0.471 0 378 0.151 0,530 0,445 0.025 0.561 0,415 0.024 0.544 0.456 0 0.677 0.423 0 0.275 0,435 0.290 0.270 0,300 0.430 I

TABLE 111. MIXTURESOF CONSTANTCOMPOSITION FOR PHASEBEHAVIOR INVESTIGATED Mole Fractions Ethylene 0.635 0.625 0.570 0.560 0.715 0.540

Vol. 36, No. 7

B

INDUSTRIAL A N D ENGfNEERltNG CHEMISTRY

July, 1944 C

a \

' 0

0.4

0.6

679

0.8

66

61

2

Figure 9.

Qualitative Phase Behavior Diagram

56

51,

46.

Cd+

Figure 7 gives a similar diagram for the 60" F. results. It differs from Figure 6 in that the temperature is above the critical temperature for pure ethylene. As a result, mixtures of vapor and liquid cannot be formed a t conditions closer t o ethylene than the dotted curve shown; this curve is the locus of compositions which have critical temperatures at 60' F. and critical pressures varying from t h a t of the ethane-ethylene system to that of the ethylene-acbtylene system at 60". Figure 8 indicates the effect of pressure and composition upon the two-phase region at 40' F. and is, in effect, a series of triangular diagrams superimposed above one another and spaced according t o the pressure scale. The three faces of the figure are the constant-temperature binary diagrams; the solid, represented by the bubble an4 dew point surfaces, shows the continuous change in phase behavior. The thickness between the bubble and dew point surfaces becomes zero along the azeotropic locus. Wit available in this investigation, it is pos ely the type of behavior which would res between those of the present investigation. Several of these quditative diagrams are presented in Figure 9. A is drawn a t 47.5' F., which corresponds to the minimum temperature of the critical locus curve of the ethylene-acetylene system and is the lowest temperature at which any mixture of ethylene and acetylene may exist in a critical state. Below 47.5' F. there is no critical locus within the ternary diagram. As the temperature rises above 47.5" F., a critical locus begins to appear which, a t 48.5', would be of the type shown in B. This temperature is below the critical of ethylene and above the minimum critical temperature of the ethylene-acetylene system. At 49.3' F., the critical temperature of ethylene, the diagram would be the type shown as C. The critical locus loop has expanded and encloses a greater portion of the ternary diagram. At 55' F. the diagram would be the type shown as D . This temperature is above the critical of ethylene, and therefore a critical point exists in the ethane-ethylene system as well as in the ethylene-acetylene system. LITERATURE CITED

(1) Azetylen Wiss. Id.,33,73 (1929). (2) Berthelot and Vieill, Cmpt. rend., 121, 424 (1895); 124, lo00 (1897). (3) Burrell and Oberfell, Bur. Mines, Tech. Paper 112 (1915). (4) Cardoso and Baume, Compt. rend., 151, 141 (1910).

INDUSTRIAL AND ENGINEERING CHEMISTRY Carter, Sage, and Lacey, T r a n s . Am. I n s t . M i n i n g JFet.

Engrs.,

142,170(1941).

Churchill, Collamore, and Kats, OiZ Gas J . , Aug. 6, 1942. Claude and Hess, Compt. rend., 124,626, 988, 996, 1000 (1897). Copson and Frolich, IND.EKQ.CHEM.,21, 1116 (1929). Dourson, Sage, and Lacey, Am. Inst. iMining Met. Engrs., Tech. P u b . 1490 (1942).

Furman (editor), “Scott’s Standard Methods of Chemical Analysis”, Vol. 11, New York, D. Van Nostrand Co., 1939. Guter, Newitt, and Ruhemann, Proc. R o g . SOC. (London), A176, No. 964, 140 (1940). Krauss, Azctogene Metallbearbeit., 28, 72 (1935). Kuenen, P h i l . M a g . , 40, 173 (1897). Ibid., 44, 174 (1895).

Lamb and Roper, J . Am. Chem. SOC.,62, 806 (1940). Loomis and Walters, Ibid., 48,2051 (1926).

Vol. 36, No. 7

(17) Maass and Wright, Ibid., 43, 1098 (1921). (18) McIntosh, J . P h y s . Chem., 11, 306 (1907). (19) Pickering, Ibid., 28, 97 (1924). (20) Porter, J . Am. Chem. Sac., 48, 2055 (1926). (21) Quinn, So.D. thesis in Chem. Eng., M.I.T., 1940. (22) Rimarski, Autogene Afetallbearbeit., 22, 134 (1929) (23) Rimarski and Konschak. I b i d . . 26. 129 (1933). (24) Rimarski and Konschak, Azetylen Wiss: I n d : , 33, 97 (1930) (25) Ibid., 35, 146 (1932). (26) Wolff, 2. angew. Chem., 11, 919 (1898). (27) Yee, Ph.D. thesis, Univ. Mich., 1936. PRESENTED before the Division of Petroleum Chemistry a t the 107th hleetCleveland. Ohio. Abstract of thesis ing of the A Y E R I C A K CxEnrrcAL SOCIETY, submitted by J. L. McCurdy to Rackham School of Graduate Studies, University of Michigan, in fulfillment for Ph.D. degree.

PROTEINmALDEHYDE PLASTICS Reaction of Formaldehyde with Beaminized Casein E).

C . Carpenter and F . E . Lovelace‘

NEW YORK STATE EXPERIMENT STATION, GENEVA, N. Y.

T

HE first paper in this The combining ratios between formaldehyde and deaminthough it may not react itseries ( 4 ) described ized casein are established over a concentration range up to self with aldehyde, greatly 6.85% formaldehyde. The general law, relating bound influences the constants remeasurements of the formaldehyde bound by acid formaldehyde to total formaldehyde, is shown to be the lated to the binding of the casein and rennet casein, and adsorption law, x KCn, Over the concentration range second mole of aldehyde. showedthat Over axviderange investigated. The value of n is the same for deaminized From the work of Dunn of aldehyde concentration, casein as for acid casein previously investigated. The and co-workers, we may exvalues for K are very different, only 45% as much aldehyde the aldehyde bound conclude that arginine binds being bound at any aldehyde concentration by deaminized pressed by the law X = KC”, One Of On the casein as by acid casein. The aldehyde bound by acid the constants having different at a casein and deaminized casein agrees closely with that exor-amino group higher aldehyde concentravalues for the different capetted from the content of certain individual amino acids in the respective proteins. t i o n , o n e m o l e on t h e seins. Some 30% more aidehyde was bound by acid caguanidino group, H&Csein than could be accounted (=NH)NHR. The lattcr for by assuming reactions with a-amino groups, side-chain amino is indicated rather than the a-position by the fact that the Sakaguchi reaction (14) for the guanidino group is negative afte groups of the diamino acids, and amide groups. It was suggested aldehyde and arginine have reacted for some time. that the binding of aldehyde by hydroxyamino acids t o form With respect to lysine, the €-amino group apparently reacts acetals should be considered a possibility, inasmuch as the interawith one mole of aldehyde before the a-amino group, and the tomic distances of the acetals involved were compatible with latter reacts eventually with the usual two moles of aldehyde. ideas of protein structure already obtained from x-ray studies. Histidine reacts with one mole of aldehyde at the a-amino Recent studies on aldehyde binding by amino acids by Dunn group and with a second mole a t higher aldehyde concentrations. and co-workers (8) and from this laboratory (6) have done much The great reactivity of the latter reaction leads one to suspect to clarify the general problem. We showed that the amide group that the second aldehyde may react with the imidazole ring of asparagine does not react with formaldehyde and that, in genrather than at the a-amino as is usual. eral, the a-amino group reacts with one mole of aldehyde to give Proline reacts with only one mole of formaldehyde. The a fairly stable methylol derivative; the latter, in turn, reacts five-membered ring structure of proline and oxyproline makes it with a second mole of aldehyde to form an unstable compound difficult to fit them into peptide chains according to modern ideas which gives up aldehyde readily and which is probably an acetal of protein structure. The least difficulty is encountered by asof the type RNHCHgOCHsOH. This structure is indicated by suming proline to occur a t the end of R peptide chain with the its properties and the fact that only in the presence of an alkyl imino group in peptide linkage. This rules out a reaction with group (such as in N-methylleucine) is the second hydrogen of the aldehyde amino group reactive with aldehyde. No reaction occurs with I n the first paper (4) we overlooked the possibility of aldehyde aldehyde when an acyl group is attached to nitrogen of the amino binding with the tyrosine side chain. However, Koebner (12) group ( 3 ) . The length and structure of the side chain, even prepared 2,6-dimethylol-4-methylphenolfrom p-cresol and forrn1 Present address. Curtico Bros. Co., Rochester, N. Y .