Active Standard ASTM D890 | Developed by Subcommittee: D01.34
Book of Standards Volume: 06.03
Historical (view previous versions of standard)
Significance and Use
3.1 Many pine chemical products contain water as a result of the processes used for their production. Typically refined products such as terpenes, pine oil, tall oil fatty acids, and distilled tall oil contain only traces of water, but crude tall oil might contain 0.5 to 2.5 % of water. Although the Karl Fischer and coulometric methods are most applicable to low levels of moisture, these can be and are used at higher levels. The azeotropic distillation method is generally used at higher levels.
1.1 These test methods cover the quantitative determination of dissolved or occluded water present in any proportion in liquid pine chemicals, such as turpentine, pinene, dipentene, pine oil, tall oil, and tall oil fatty acids. Three methods of moisture testing are included. The Karl Fisher titration method is the preferred method for testing tall oil, Test Methods D803.
1.1.1 The Karl Fischer Titration method is based on the reaction between water and a complex reagent2 consisting of iodine, sulfur dioxide, pyridine, and methanol, whereby the iodine is converted to a colorless compound. The appearance of a persistent iodine color in the reaction mixture indicates the complete removal of free water by reaction with the reagent, and the endpoint may be measured colorimetrically. Automatic titrators find this endpoint by the restoration of a current strength when the resistance provided by the presence of water is eliminated. Amperometric automatic titrators find this endpoint by detecting the current flow that occurs once water is eliminated.
1.1.2 The coulometric titration method determines water content by electronic integration of a current sufficient to generate the precise amount of iodine from the required reagent to react with the water in the sample.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D803 Test Methods for Testing Tall Oil
D1364 Test Method for Water in Volatile Solvents (Karl Fischer Reagent Titration Method)
ICS Number Code 87.060.30 (Solvents)