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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Chemistry and Principles Karl Fischer titration proceeds according to a reaction with a two-step mechanism in which sulfur dioxide initially reacts with an alcohol ROH to form an ester intermediate which is neutralized, or buffered, by an appropriate organic base RN. Understanding Oil’s Saturation Point. The following reactions represent this two-step mechanism. Best Ways to Test for Water in Oil.
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. KF analysis is a versatile and robust analytical tool for water content analysis in oil asrm, and can detect d634 in any of three states commonly found in oils.
Types of Titration Volumetric KF Volumetric KF proceeds in the conventional manner of a classic titration, in that the titrant containing iodine is added mechanically to the solvent containing the sample by the titrator’s burette Figure 1.
Additionally, water has been known to cause certain oil additives to precipitate out, as well as to chemically attack some additives. Techniques for Successful KF of Oil Samples Direct Titration Sample solubility issues may be overcome by using co-solvents such as chloroform, toluene or xylene to increase the solvent capacity of conventional KF reagents in the titration cell.
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 d6340 cell Figure 2.
Metrohm: Coulometric Karl Fischer Titration for ASTM D6304
Used oils may also contain contaminants that can potentially interfere with direct KF analysis, such as trace metals, polyaromatic hydrocarbons, polychlorinated biphenyls, as well v6304 various products of incomplete combustion.
These include corrosion, erosion, etching and hydrogen embrittlement. In two-component KF, the titrant contains only an alcoholic solution of iodine, while the solvent contains the other ingredients needed for the reaction. Volumetric or coulometric KF methods, utilizing either direct titration or the oil evaporator technique, can be used to quantify water in oil samples from trace amounts to asrm.
Since its invention by German petroleum chemist Dr. 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. Strategies for Removing Water from Ashm.
Coulometric KF Titration for ASTM D
Fundamentals of Volumetric Karl Fischer Titration. Volumetric KF is most accurate in the range of ppm to percent water. Recommended Sample Sizes for KF Analysis Sample Size Selection For both d63044 and indirect KF methods, sample size selection is critical for minimizing errors associated with sample weighing, transfer and asstm.
Toggle navigation Toggle search. A number of lubricating oil additives are reactive and are known to interfere with direct KF titration. 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.
Corresponding reduction of hydride to hydrogen takes place at the cathode. Modern Instrumental Methods and Techniques. The KF method does not suffer from the same issues and limitations associated with the other techniques described above, and a number of recent advances in titrator instrumentation and reagent formulations have further improved the accuracy and reproducibility of KF analyses. The two types of volumetric KF differ in the exact composition of titrant x6304 solvent.
These include aldehydes, higher phenols, modified mercaptans, ketoacids, polysiloxanes, sulfides and metal oxides. Axtm 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 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. In other words, the larger the sample, the less error is introduced into the analysis by sample weighing, transfer and other handling.
Reactivity Certain compounds in the oil will undergo interfering side reactions either with methanol or iodine components of KF reagents.
Analyzing Water in Oil
High water content of lubricating oils negatively impacts the operation and longevity of the oils and the mechanical equipment components being lubricated. Finding the Source of Water Contamination in Oil. Oils have limited solubility in alcohols, such as methanol, which are typically used in common KF reagent formulations, while they are fully soluble in organic solvents like chloroform, toluene and xylene.
Furthermore, neither aastm indication nor the hot plate test can be used to reliably quantify the water present. That is, while the iodine in the KF reagent is reacting with water, there is no free iodine present in the titration cell, and a high voltage is required to maintain the set polarization current at the double platinum pin indicator electrode.
Distillation methods, such as ASTM D95 and D provide better quantitative data in the range of approximately ppm to 25 percent, but require large sample sizes and involve long asstm times, typically 60 to minutes. However, alcohols cannot be completely removed from KF reagents, because the presence of alcohol is required by the mechanism of the KF reaction.
The end-point determination in KF titration occurs by means of bivoltametric indication. 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, d66304 component of the coulometric titration cell Figure 2.
In coulometry, the quantity of iodine generated corresponding to the amount of water present is calculated by the titrator on the basis of current mA and time sec. Water in oils can occur in dissolved, emulsified and free states. However, neither of these methods can detect dissolved water or reproducibly detect trace levels of emulsified water.
Sample Size and Reproducibility As with any analytical technique, the sampling error in KF analysis is inversely proportional to the sample size. Current Issue Archive Advertise.