Freezing point, curves

Erstarnmgs-kurve, /. freezing-point curve, -punkt, m. freezing point setting point, solidification point coagulation point, -warme, /. heat evolved on solidification, heat of fusion. 

The description of the various types of freezing-point curves... 

From the shape of the maximum, some information can be obtained as to the extent of dissociation of the compound in the liquid state thus the maximum on the freezing-point curve of CaCl2 and H20 is very broad and flat, an indication of the almost complete dissociation of the compound CaCl2. 6HaO in the fused condition (Roozeboom and Aten, 1905 Kremann, 1906). 

This stearolic acid has been thoroughly characterized 3 6 by the freezing-point curve, ultraviolet and infrared spectra, ozonization, and hydrogenation. It has been shown to be free both of positional isomers and of olefinic acids such as oleic and elaidic acids. Its properties include m.p. 46-46.5°, iodine number (Wijs titration, 30 minutes) 89.5, d 5 1.4510, d 5 1.4484, neutral equivalent 279.2-279.6 (theory 280.4), hydrogen uptake 95-100% of theory for a triple bond. The last trace of color is difficult to remove by recrystallization from petroleum ether. It can be removed, however, by crystallization from a 20-30% solution in acetone at —5 to —8°, or from an 8-10% solution at —20°, or by distillation (b.p. 189-190°/2mm.). 

Table 15.3. Calculated freezing point curves for o- and p-xylene 25)...

J. C. Randall, Phillips Petroleum, Oklahoma I was interested in your linewidth curves vs temperature in which you essentially had the melting point curves. Did you do any freezing point curves ... 

Atomic per cent Fig. 25.—Freezing Point Curve of Iodine and Chlorine. 

Fig. 27.—Freezing Point Curves of Mixtures of Iodine and Bromine.

Freezing-point Curve Iodine-Potassium Iodide. 

Fig. 38.—Freezing Point Curves of the Binary System NaaS—S.

In other cases, a freezing-point curve represented in Fig. 15 is obtained. In this curve, the point C is a maximum freezing point between D and E and indicates that a compound has been formed between A and B,... 

Trisulphur tetrachloride separated over the narrow range of 5G-G to 59-2 atoms of chlorine per cent. (i.c. 01 -G per Cent, chlorine) after seeding with a sample cooled in liquid air to prevent the separation of a liquid phase. It was of a flocculcnt nature, very different from the granular monochloride or the pasty dichloride. As this different appearance coincided with the limits of a section of the broken freezing-point curve, it was regarded as evidence of the separation of a compound intermediate in composition between the monochloride and dichloride. 

Sulphur and Iodine.—Various methods have been described for the preparation of compounds of iodine and sulphur,3 but to-day the products are regarded merely as mixtures of the elements.1 In solution in carbon disulphide, iodine and sulphur exist side by side permanently uncombined. The freezing-point curves for mixtures of the two elements,5 as also the vapour pressure curve of the fusion products,6 likewise give no indication whatever of chemical combination, although sulphur forms a solid solution in iodine. A further proof of the absence of combination is the fact that when dissolved in iodine, sulphur has a normal molecular weight, determined eryoseopically, only a little below that required for S8.7 The present condition of our knowledge, therefore, may be summed up in the statement that no definite compound of sulphur and iodine has yet been obtained.8... 

Chlorine combines with the gas when the mixture is exposed to sunlight or when the sulphur dioxide is employed in solution in acetic acid or in camphor, the product being sulphuryl chloride 3 no combination occurs in the dark in the absence of a catalyst. In the presence of water the products are sulphuric acid and hydrochloric acid.4 Bromine does not combine in this manner, nor does hydrogen chloride, the freezing-point curve of the latter with sulphur dioxide showing only the formation of a eutectic mixture.5... 

Many aromatic hydrocarbons, for example, benzene, ethylbenzene, toluene, cymene and tetrahydronaphthalene, yield additive compounds.5 Such are also formed with liquid cyclic hydrocarbons in the absence of moisture and phenols, and use has been made of this fact to remove sulphur dioxide from a dry gas containing it.6 Additive compounds are also formed with methyl alcohol, thus CH30H.S02 and 2CH30H.S02, the existence of which has been demonstrated definitely by means of the freezing-point curve.7 The additive compound with camphor has already been mentioned (p. 109). 

Tellurium and iodine, in the molten condition, are miscible in all proportions, and the system tellurium-iodine has been examined from the thermo-analytical standpoint, the freezing-point curve giving indications only of the formation of a tetra-iodide, Tel4, in the fused mixture.1... 

Cadmium Arsenides.—The freezing point, density and atomic volume curves indicate the existence of two arsenides, Cd3As2and CdAs2.n The freezing point curve was obtained by cooling mixtures of the elements melted under fused alkali chloride no mixed crystals were observed. Two other arsenides have been described Cd6As, said to... 

The freezing point curve of mixtures of chlorine and arsenic trichloride is smooth and shows no indication of combination.4... 

Only one bromide of arsenic has been isolated this is the tribromide, AsBrs, and an investigation of the system AsBr3-Br2 gives no indication of the formation of a higher bromide. The freezing point curve shows a eutectic point at -34° C. and 81 atomic per cent, of bromine.5... 

Cryoscopic and ebullioscopic measurements indicate that the halides of phosphorus, arsenic, antimony, titanium and tin readily undergo reciprocal interaction with interchange of halogen atoms and that mixed halides can be formed11 (see p. 103). Melting and freezing point curves are, however, generally of the eutectic or mixed crystal types, without... 

Borodowski1 failed to obtain evidence of the formation of this sulphide in his study of the freezing point curves (see p. 237) because, with mixtures containing 20 to 60 molar per cent, of arsenic, the products are viscous and do not give definite freezing points. 

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