Solidifying points, determination

Many oils possess the property of becoming solid at temperatures slightly below the ordinary, and a determination of the soliditying- or melting-points becomes an important criterion of purity in these cases. The melting-point is not usually the same as the solidifying-point, on account of the peculiar properties of bodies, included under the term superfusion, etc. In addition, the temperature recorded differs some-... 

On account of the variability of the proportions of A-sulphur, p,-sulphur and 77-sulphur in the liquid, the solidifying-point of molten sulphur is not constant, but may range from 114° to 117° C. or even more widely. The freezing-point of pure A-sulphur can be determined by calculation, the result, 119-25° C., almost coinciding with the temperature... 

For the exact determination of the solidifying point of some essential oils use may be made of the apparatus shown in Fig. 62. 

In the case of some compounds with low melting-point and of fats and oils, which are not individual compounds, the temperature at which the liquid substance solidifies is determined rather than the melting-point. This is termed the solidification-point or freezing-point. 

Melting and Solidifying-Points—Boiling-Point and Distillation— Determination of Esters—Determination of Alcohols— Tables for the Calculation of Esters and Alcohols—Separate DMermination of Citronellol in Presence of Gwaniol—Determination of Aldehydes and Ketones— Miscellaneous Processes—Determination of Phenols—Detection of Chlorine—Determination of Hydrocarbons—Detection of some Common Adulterants. 

The solvents were evaporated in vacuo, and the residue was taken up in 80 ml of 3M hydrochloric acid. After addition of 220 ml of water, the insoluble material was filtered off, washed with 100 ml of water and then dried. The insoluble material weighed 9.5 g and was mainly unreacted bromo compound. The filtrate was reacted with 50 ml of 7 M NaOH, extracted three times with methylene chloride (50 m -t 2 x 25 ml portions), dried over potassium carbonate, and then evaporated. The yield of residue was 26.8 g which corresponds to 71.4% of the theoretical yield. This residue was a colorless solidifying oil and was dissolved in 200 ml chloroform. Hydrogen chloride was bubbled in until a sample of the solution tested acidic to wet pH indicator paper. A precipitate was obtained and recovered by filtration. The precipitate was washed with chloroform and dried. The melting point was determined to be from 246 Cto247.5°C. 

---