Thermal investigation of solid-liquid equilibrium in the naphthalene (and some dimethyl derivatives)-picric acid systems

Abstract

The equilibria of the naphthalene-picric acid and the 2,3-and 2,6-dimethylnaphthalene-picric acid systems were subjected to thermal investigation.The naphthalene-picric acid system was earlier investigated by Kremann, Sapozhnikow and others [1,5]. In view of the divergence of their data, reinvestigation of this system was considered necessary. Experimental MaterialsChemically pure picric acid (2,4,6-TNF) (POCh, Gliwice) was dissolved in hot water and neutralized with a saturated solution of sodium carbonate. The sodium salt was treated with hot dilute sulfuric acid to give picric acid (m.p. 122.6 "~) of 99.7 % purity (determined by gas-chromatography).2,3-dimethylnaphthalene (2,3-DMN) and 2,6-dimethylnaphthalene (2,6-DMN) (BDH) were purified by rectification using a high-efficiency rectifying column to give 2,3-DMN (m.p. 105 ~ of 99.98 % purity and 2,6-DMN (m.p. 114.4 ~ of 99.9(~ )/o purity (determined by gas-chromatography).Naphthalene (POCh, Gliwice) was heated with bentonite and purified by rectification to give a product of 99.99 % purity with m.p. 80.8 ~ Apparatus and procedure 5 g samples of mixtures which differed in composition by weight in steps of 10 were prepared for measurements and ground to a uniform mass.Differential thermal (DTA) curves were recorded by means of a Paulik-PaulikErdey derNatograph, using 0.3 g samples in the smallest platinum crucible. The heating rate was 0.9 ~ per rain. in the range 20-1500 ~ The reference substance was Al20 3.Crystal decay temperature examination by Hill's method [3] as modified by Swierczek [4] was applied as a supplementary measurement. 4 g samples of mixtures of the same compositions as above were used. The heating rate near the melt-3 ~. Thermal Anal. 19, 1980