Distillation methods, such as ASTM D95 and D provide better . This innovative KF technique is incorporated in ASTM D (Method B) and is applicable. If a crackle test is positive, further testing is needed to quantify the amount of water by using The Karl Fischer Water titration by ASTM D A measured. Feb 24, The KF Coulometer from Metrohm is the perfect instrument to satisfy ASTM D
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Strategies for Removing Water from Oil.
Corresponding reduction of hydride to hydrogen takes place at the cathode. Alternatively, specially preformulated KF reagents incorporating one or several of these solvents are commercially available for both volumetric and coulometric KF. The procedure involves adding the oil sample to the solvent present in the evaporation chamber where it dissolves in the solvent, and in the process forms a binary azeotrope between the d63044 and the sample’s water content.
Key Components of a Modern Volumetric KF Titrator Coulometric KF In coulometric KF, the iodine needed by the KF reaction is not present in the KF reagent, but is instead generated electrochemically in situ from iodide at the anode of the generator electrode, a zstm of the coulometric titration cell Figure 2.
Since its invention by German petroleum chemist Dr.
In coulometry, the d630 of iodine generated corresponding to the amount of water present is calculated by the titrator on the basis of current mA and time sec. In other words, the larger the sample, the less error is introduced into the analysis by sample weighing, transfer and other handling.
Types of Titration Volumetric KF Volumetric KF proceeds in the conventional manner of ast, classic titration, in that the titrant containing iodine is added mechanically to the solvent containing the sample by the titrator’s burette Figure 1.
The KF method does not suffer from the same issues and limitations associated with the other techniques described above, and a astn of recent advances in titrator instrumentation and reagent formulations have further improved the accuracy and reproducibility of KF analyses. Coulometric KF In coulometric KF, the iodine needed by the KF reaction is not present in the KF reagent, but is instead generated electrochemically in situ from iodide at the anode of the generator electrode, a component of the coulometric titration cell Figure 2.
In one-component KF, the titrant usually referred to as a CombiTitrant or a composite contains all the ingredients needed for the KF reaction, namely iodine, sulfur dioxide, base axtm a suitable alcohol, while the solvent is typically dry methanol. High water astk of lubricating oils negatively impacts the operation and longevity of the oils and the mechanical equipment components being lubricated.
Water in oils can occur in dissolved, emulsified and free states. Create your own user feedback survey.
With both types of volumetric KF, imidazole is the base used most frequently as a buffer to maintain optimal pH for the reaction. For those oil samples which fail to adequately dissolve even when using KF reagents formulated with organic co-solvents, or those that are suspected of containing interfering compounds, an indirect KF analysis using an oil evaporator is recommended, as described below.
Modern Instrumental Methods and Techniques. Furthermore, neither visual indication nor the hot plate test can be used to reliably quantify the water present.
The technique also offers other substantial advantages over more conventional hot plate crackle test and distillation methods, and it has been incorporated into numerous ASTM standards. However, neither of these methods can detect dissolved water or reproducibly detect trace levels of d6034 water.
However, due to solubility and reactivity issues described above, analysts often drastically reduce sample size, which tends to reduce the reproducibility of test results.
Once all the water has reacted with the iodine, trace quantities of free iodine appear in the titration cell, causing a drop in voltage necessary to keep the polarization current constant, which in turn signals the end-point of the titration.
The subsequent oxidation of the alkylsulfite salt to an alkylsulfate salt by asm consumes water in a 1: Additionally, water has been known to cause certain oil additives to precipitate out, as well as to chemically attack some additives.
Recommended Sample Sizes for KF Analysis Sample Size Selection For both direct and indirect KF methods, sample size selection is critical for minimizing errors associated with sample weighing, transfer and injection. Coulometric KF is most accurate in the range of 1 ppm to 5 percent water.
Understanding Oil’s Saturation Point.
Visual indication is reliable for quantifying water content only in the free state, while the hot plate crackle test can be used to detect free and emulsified water. Current Issue Archive Advertise. Reactivity Certain compounds in the oil will undergo interfering side reactions either with methanol or iodine components of KF reagents. A number of lubricating oil additives are reactive and are known to interfere with direct KF titration.
Volumetric KF is most accurate in the range of ppm to percent water. Karl Fischer inKarl Fischer KF analysis has progressed from an esoteric laboratory procedure to a widely accepted instrumental method routinely used for water determination in the petrochemical industry.
Best Ways to Test for Water in Oil. The following reactions represent this two-step mechanism. These include corrosion, erosion, etching and hydrogen embrittlement.