Studies on the Nitrotoluenes. IV—The Three-Component System:p-Nitrotoluene, 1,2,4-Dinitrotoluene, 1,2,4,6-Trinitrotoluene

James M. Bell, Charles H. Herty
1919 Journal of Industrial & Engineering Chemistry  
I n many of our cooling curves we find t h a t the temperature of point B , Fig. J , a t which crystals first appear, agrees with t h e values recorded by Giua. We have plotted his results on Fig. 3 for DNT-TNT. These freezing-point curves do not intersect a t t h e eutectic point, a condition which is interpreted as indicating the existence of a compound of t h e components. Of course, if Giua's data are taken as correct, this must be t h e proper interpretation of the curves. 80"-70 '-60't b
more » ... s. 80"-70 '-60't b u, h $ 50? ki 40% 30" 20' 100 Molecu/ar Per cent FIG. 5 Thus in all three of these binary systems Giua claims the existence of compounds over a narrow range of concentration. I n none of t h e cases did we obtain a result other t h a n t h e intersection of t h e freezing-point curves a t t h e temperature found for the eutectic point. Giua's conclusions therefore regarding t h e existence of molecular compounds in these three cases seem t o be erroneous. In t h e first paper of this series,' t h e effect of various nitrotoluenes on t h e freezing point of trinitroxylene was studied and the results were found t o accord fairly well with a formula based on the assumption t h a t these mixtures were "ideal solutions." It is possible t o test the validity of the assumption of "ideal solutions" in another way. Thus t h e freezing point of such a mixture should depend on the molecular fraction of t h e freezing component and not on the nature of the other component or components, provided the components are of like chemical character. When, therefore, the freezing-point curves are drawn using molecular percentages, the curves should coincide. I n Pig. 5 are shown t h e freezing points of t h e nitrotoluenes as influenced by other substances. The curves for M N T and t h e curves for T N T fall quite close together, 1 THIS JOURNAL, 11 (1919), 1025. and it is concluded t h a t the mixtures obey t h e ideal solution law. The curves for D N T do not lie so close together. The effect of p-toluidine on the freezing point of D N T is from t h e results of Mremann and Petritschek-* The cause or causes of the deviation may be found when anoQer investigation now in progress has been completed. The formula based on "ideal solutions" involves the latent heat of fusion, regarding which no data could be found in the literature. The direct determination of t h e latent heat of fusion of all of these nitrotoluenes will form another paper of this series. S U M M A R Y I n this paper we have given a discussion of t h e melting points of M N T , D N T and T N T , a discusqion of t h e interpretation of cooling curves, and t h e d a t a for the three binary systems of these nitrotoluenes. I n t h e third paper of this series we have given t h e results of a study of the three binary systems of t h e nitrotoluenes: $-Nitrotoluene ( M N T ) , I , 2,4-dinitrotoluene ( D K T ) , and I , 2,4,6-trinitrotoluene ( T N T ) . The present paper contains the resuIts of a study of t h e ternary system of these components. We have again employed the cooling-curve method of finding the temperatures a t which t h e various solid phases appear, using t h e extrapolation method of overcoming t h e difficulty introduced b y t h e phenomenon of supercooling. This method was described in detail in t h e paper above referred to.3 L Y U Z Tim e FIG. 1 For a binary mixture there are two freezing points: The primary freezing point a t which t h e first solid appears, and t h e binary eutectic point where t h e two solids are in equilibrium with t h e melt. For a ternary mixture there are three freezing points: The primary freezing point a t which t h e first solid appears, t h e secondary freezing point a t which the second solid appears, and the ternary eutectic point where all three solids are in equilibrium with t h e melt or eutectic mixture. The last temperature was not difficult t o determine 1 Monatsh., 88 (1917). 385. * This paper is the fourth of a series dealing with the freezing points and thermal properties of the nitrotoluenes, the investigation having been undertaken at the request of the Division of Chemistry and Chemical
doi:10.1021/ie50120a012 fatcat:3hrzmbzpjrcwrfnhsesbpjnyoq