308
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
shows why we were unable t o obtain points where stable O N T was the solid phase, for neither binary eutectic, ONT-MNT or ONT-DNT, was found in the presence of metastable O N T . A11 the points in the diagram in the top field represent liquids saturated with respect t o stable ONT. Again we have observed the tendency for great supercooling with respect t o D N T , and therefore we have been compelled t o seed with crystals of t h a t substance. The approach t o equilibrium after seeding is also somewhat slow, and rather long extrapolations have been necessary. The position of the boundary curves has been established by the method of the paper already cited. The freezing points of mixtures with a constant percentage of one component have been plotted. The points lie on two curves which intersect a t the boundary curve, and t h e composition and temperature given by the plot establish one point on the boundary curve. The complete boundary curve may be obtained by finding a number of such points. T h e
Vol. 13. NO.f
intersection of the three boundary curves fixes t h e composition of the ternary eutectic, found in this case t o be 62 per cent ONT, 19 per cent M N T , and 19 per cent DNT. For most of the low-temperature work we used a bath of ice and salt, but for temperatures in the neighborhood of the ternary eutectic a lower temperature was necessary. For this purpose we used a bath of mixed carbon tetrachloride and gasoline in which was a coil of metal tubing connected with a tank of liquid ammonia, tilted so as t o deliver the liquid a t the control valve. The evaporation of the tiquid into the metal coil lowered t h e temperature sufficiently t o obtain cooling curves for the lowest freezing mixtures. The ternary eutectic temperature was reached by first obtaining the binary eutectic mixture, ONTM N T , and by adding D N T in small quantities. Each addition lowered the temperature until no more D N T would pass into the melt. When the liquid is saturated with D N T also, t h e ternary eutectic h a s been reached, in this case a t -20.1'.
Studies on the Nitrotoluenes. VII-The Three-Component System: p-Nitrotoluene, o-Nitrotoluene, 1,2,4,6-Trinitrotol~ene*~~ By James M.Bell and Fletcher H. Spry UNIVERSITY
OF
NORTH CAROLINA, CHAPELHILL, N. C .
All the binary systems of the components: p nitrotoluene ( M K T ) , o-nitrotoluene ( O N T ) , and 1,2,4,6-trinitrotoluene ( T N T ) have already been described in previous articles of this ~ e r i e s . ~I n each case the freezing-point curves consist of two lines intersecting in a eutectic point. There is no compound of the components in any of the cases. 0 NT -4.45'
these crystals being necessary. The accompanying table comprises only data for three-component mixtures, the temperatures along the sides of the triangle having already been recorded in the articles referred t o above. The positions of the boundary curves and of the eutectic point were determined by the method described by Bell and Cordon.' The diagram shows the boundary curves with 5' isothermals. T h e eutectic temperature and composition are -19.5" and 65.5 per cent ONT, 19.5 per cent M N T , 15 per cent T N T . I n this study we have met only the simplest conditions. There are no binary and no ternary compounds. ONT 10
10 10 10 10
Per cent by Weight MNT 80 70 60
jo
30 20
10 60 50 40 30 20 10 50
Received December 21, 1920. 1 This paper is the seventh of a series dealing with the freezing points and thermal properties of the nitrotoluenes. the investigation having been undertaken a t the request of the Division of Chemistry and Chemical Technology of the National Research Council. 8 MNT-ONT and TNT-ONT. Bell, Cordon, Spry and White, THISJOURNAL, 13 (19211, 59; MNT-TNT, Bell and Herty,Ibid., 11 (1919), 1124. 1
40 30 20
10
50 50 50
49.4
70
57.9
80 10
65.65 35.1 29.85
20
30 40 50
60 70
10 20
30 40 50
60
IO 20 30 40 50
23.4
28.64 38.5 48.4. 57.9 27.43 21 .o 13.8 27.23 38.8 47.4 18.85 10.85 12.35 26.63 37.6
10
7.5
30
20 30 40 10 20 30 10 20 IO
-3.8 9.95 25.47
20 10
30 20
60 70
10 20
70
10 10
1
38.4
60
40 .~
60 60
80
c.
41.9 37.4 32.2 29.0
50 40
20 10 70 60 50 40
I n the study of the three-component system we have followed the methods already outlined in these articles. The freezing points where O N T is t h e solid phase refer t o the stable form (P-ONT), seeding with
Freezing Point TNT
T H KJOURNAL, ~ 13 (1921), 307.
--18.5
-12.0 8.6 -16.3 -10.5 -1 1.9
