BIKARY SYSTEMS OF C E R T A I S NITROTOLUENES WITH SALICYLIC ACID* BY H. D. CROCKFORD AND F. W. ZURBURG
The purpose of this investigation was to determine the temperaturecomposition diagrams for the systems: z-4-6-trinitrotoluene, z-4-dinitrotoluene, and p-nitrotoluene, with salicylic acid. The work is a continuation
20
4c
60
80
IC
FIG.I
of a series of investigations which have been carried on by James M. Bell' and his co-workers on the subject of the nitrotoluenes in the Department of Chemistry of the University of North Carolina. * From the Chemical Laboratory of the University of North Carolina. 'Bell and Sawver: J. Ind. Eng. Chem., 11, Iozj; Bell and Cummings: 1028; Bell and Herty: 1 1 2 4 ; 1 1 2 6(1919);Bell, Cordon, Spry and White: 13, 59; Bell and Cordon! 307; Bell and Spry: 308 ( 1 9 2 1 ) ;Bel1 and McEwen: 14, 536 (1922).
SYSTEMS O F NITROTOLUESES WITH SALICYLIC A C I D
215
Purification of Material. The salicylic acid was prepared by twice recrystallizing C.P. grade acid from water. A constant melting point of I j8.3OC was secured. The nitrotoluenes were purified by two crystallizations from hot carbon tetrachloride followed by one crystallization from hot ethyl alcohol. The following melting points were obtained: 2-4-6-trinitrotoluene, 80.1OC; 2-4-dinitrotoluene, 69.3"C; p-nitrotoluene, 5 1.4'C. Experimental Procedure. The cooling curves of various mixtures of about twenty grams total weight were obtained by placing the sample in a six-inch test tube, which was air-jacketed in a test tube of larger diameter, which in turn was placed in an Erlenmeyer flask containing Nujol, the system being then heated to a point above the fusion temperature of the mixture and allowed to cool at room temperature. Thermometer readings were made on the melt at half-minute intervals, the melt being constantly stirred with a glass-loop stirrer during the cooling process. The thermometers used were graduated in I/IO"C intervals and were standardized by comparison with thermometers certified by the Bureau of Standards. All temperature values have been corrected for stem exposure. I n obtaining the freezing points from the cooling curves the method of interpretation proposed by Bell and Hertyl was followed. Results. Tables I, 11, and I11 give the freezing points for the various mixtures. The temperature-composition diagrams are plotted in Fig. I . Concentrations are expressed in mol percents.
TABLE I
rcSalicyrlic
yc TST
Acid IO0
90 80 70 59.9
55.1
F.P.
% Salicylic Acid
0
158.3'
IO
152.7
20
30 40. I 44,9
I47 1 140.6 134.0 130. I
yo P S T
FP
'
Yc TST
40.9 30 19.9
80.1
IO
90
F.P.
59.1
120.0
70
3
97
107.9 93.4 76,3 79.0
0
IO0
80.I
TABLE I1 7 Salicylic Acid IO0
89.9 79.8 69.8 61.2 50.1 39.7 1
0
158.3'C
10.1
I52
20.2
145.8 139.0 131 . o 123.9 114.0
30.2 38.8 49.9 60,3
.o
J. Ind. Eng. Chem., 11, 1124 (1919).
% Salicylic
yc PST
29.7 19.5
70.3
102.6
80.5
88 . o
87.5 94.9 98,I
68.3 49.4 50.45
Acid
12.5
5.1 1.9 0
I00
FP
51.4
216
H. D. CROCKFORD A S D F. W. ZCRBCRG
TABLE I11 % Salicylic
7 'D S T
FP
Acid IO0
91.2 84.4 74.6 64.4
yo Salicylic
7; DST
FP
51.4 60.3
124 5
Acid 0
8.8 1j.6 25.4 35.6
158.3OC 154.3 IjO.5
134.0 137.2
48.6 39.7 29.3 20.4 10.1 2
0
.o
70.7
79.6 89.9 98 . 0 100.00
113 . 4 102.3 86.8 66.3 68.4 69.3
