Determination mixed aniline point

Solubility of resins can be predicted in a similar way as for the solubility of polychloroprene rubbers in a solvent mixture (see Section 5.5) by means of solubility diagrams (plots of the hydrogen bonding index (y) against the solubility parameter (5). Another more simple way to determine the solubility of resins is the determination of the cloud point, the aniline and the mixed aniline points. 

Of the petroleum solvents, the aromatic fractions are much better solvents for DDT than the paraffinic fraction. The limited solubility of DDT in the paraffinic fraction, representative of straight-run petroleum oils, shows that such oils alone cannot be used as solvents in concentrated DDT solutions. An auxiliary solvent would have to be used to prepare concentrated solutions with them. It was not possible to correlate solubility with mixed aniline point and aromatic content. This was presumably due to differences in the solubility of DDT in the individual hydrocarbons present which included both monocyclic and dicyclic types. No attempt was made to determine the amount of the individual hydrocarbons in the aromatic fractions. 

The test method for the determination of aniline point and mixed aniline point of hydrocarbon solvents (ASTM D-611, IP 2) is a means for determining the solvent power of naphtha by estimating of the relative amounts of the various hydrocarbon constituents. It is a more precise technique than the method for kauri-butanol number (ASTM D-1133). 

Several tests that are usually applied to the lower-molecular-weight colorless (or light-colored) products are not applied to residual fuel oil. For example, test methods such as those designed for the determination of the aniline point (or mixed aniline point) (ASTM D-611, IP 2) and the cloud point (ASTM D-2500, ASTM D-5771, ASTM D-5772, ASTM D-5773) can suffer from visibility effects because of the color of the fuel oil. 

ISO 2977-97. Petroleum products and hydrocarbon solvents - Determination of aniline point and mixed aniline point. 

The aniline point (ASTM D 611) is the lower equilibrium solution temperature for equal volumes of aniline and solvent. w-Heptane is the standard hydrocarbon solvent with an aniline point of 69.3 "C. The aniline point decreases from approx. 90°C for isoparaffins to 10°C for solvents with a medium aromatic content. Highly aromatic solvents result in values below 0°C so that the aniline can crystallise from the mixture. Mixed aniline points (ASTM D 1012) are used in these cases. This is the minimum equilibrium solution temperature of a mixture of two volumes of aniline, one volume of solvent and one volume of w-heptane. The relationship between the KB-number and aniline point for zero to medium aromatic content hydrocarbon solvents is shown in Figure 2.1. Figure 2.2 demonstrates the relationship between aniline and mixed aniline points. Toluene/ i-heptane blends have been used for its determination. The relationship between KB-number and mixed aniline points for solvents with a medium to high aromatic contents is given in Figure 2.3. 

There may be certain lubricants (with very high aromatic content) which when mixed with equal volume of aniline may remain completely miscible and separation into different phases may not be observed even at the time of solidification. For determining such low aniline imiiits, 1 volume of sample is mixed with 2 volumes of aniline and 1 volume of a suitable diluent (n-hexane or -heptane). Addition of the diluent lowers the miscibility of aniline with the sample and so with decrease in Icmjrerature, separation of phases can be easily observed. The equilibrium solution temperature observed under these conditions is known as Mixed Aniline Point, which can be used in the. same way as the Standard Aniline Point. 

These test methods also cover the determination of the mixed aniline point of petroleum products and hydrocarbon solvents having aniline points below the temperature at which aniline will crystallize from the aniline-sample mixture. 

The critical solution temperature is the minimum or maximum temperature at which two liquids mix in all proportions. This compilation by A. W. Francis provides this data for over 6000 systems, shows how it can be determined or estimated, and gives 800 aniline point observations. Borax to Boranes. 

In practice, in order to detect phosgene mixed with air or other inert gas by this method, it is sufficient to bubble the gas mixture under test through a few ml. of water saturated with aniline in the cold (3 gm. aniline in 100 ml. water). A white crystalline precipitate forms which can be easily seen, and, if necessary, confirmed by microscopic examination (rhombic prisms) or by a determination of the melting point (236° C.). 

---