Kauri-butanol test method

While the Hildebrand solubility parameter is justified on theoretical concepts, the Kauri butanol test is an empirical method of testing based on the solubility of a natural gum in hydrocarbon solvents. It is a good guide to the solubility of resins in paraffinic, naphthenic and aromatic hydrocarbons and some chlorohydrocarbons. Many of the hydrocarbons used in industry are mixtures, such as special boiling point spirits and white spirit, and it is easier to measure their solvent performance rather than to try to calculate it (Table 13.5). 

Kauri-butanol number A measurement of solvent strength for hydrocarbon solvents the higher the Kauri-butanol (KB) value, the stronger the solvency the test method (ASTM D1133) is based on the principle that Kauri resin is readily soluble in butyl alcohol but not in hydrocarbon solvents and that the resin solution will tolerate only a certain amount of dilution and is reflected as cloudiness when the resin starts to come out of solution solvents such as toluene can be added in a greater amount (and thus have a higher KB value) than weaker solvents such as hexane. 

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). 

Existing methods use physical measurements and require suitable standards. Tests such as aniline point (ASTM D-611) and kauri-butanol number (ASTM D-1133) are of a somewhat empirical nature and can serve a useful function as control tests. Naphtha composition, however, is monitored mainly by gas chromatography, and although most of the methods may have been developed for gasoline (ASTM D-2427, ASTM D-6296), the applicability of the methods to naphtha is sound. 

Standard test method for Kauri-Butanol value of hydrocarbon solvents, ASTM D1133-02, Book of Standards, Vol. 6.04. 

Standard Test Method for Kauri-Butanol Value of Hydrocarbon Solvents,... 

The Kauri-butanol value, used to rate solvency of hydrocarbon solvents, is defined in ASTM Method D 1133 as the volume in milliliters of the hydrocarbon solvent at 25 °C that is required to produce a defined degree of turbidity when titrated into a specified quantity of a standard clear solution of kauri resin in n-butyl alcohol. Kauri-butanol values range from approximately 20 for the weakest hydrocarbon solvents to more than 100 for stronger aromatic solvents. The test is limited to hydrocarbon solvents and is not applicable to oxygenated solvents. As Kauri resin (a natural resin) is no longer easily available, the test has not maintained its acceptance in the industry. Aniline point (or mixed aniline point), another measure of solvency of hydrocarbon solvents, is more accepted. The ani-... 

All these empirical test methods for arbitrary rating of solvency have the common limitation that they compare the ability of a solvent to keep in solution one solute, namely kauri resin, aniline and nitrocellulose for Kauri-butanol value, aniline point and toluene... 

Bias—Test bias can result if the kauri-butanol solution is not carefully standardized and adjusted (see 7.2 and 7.3). The test method has no definitive bias statement because the value of the test result is defined only in terms of the test method. 

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