D4928_12_12

Prepare the apparatus for use as described in section 10 of the written standard. Ensure the syringe is of suitable capacity. See 7.3 of the written standard and table 1. Immediately after the mixing step described in 9.6 of the written standard, withdraw at least three portions of the sample and discard to waste. Immediately withdraw a fourth portion. Wipe the needle clean. Weigh the syringe and contents to the nearest 0.1 milligram and inject the test specimen into the Karl Fischer reagent below the surface of the reagent in the titration cell. Withdraw the syringe and reweigh the syringe to the nearest 0.1 milligram. After the endpoint is reached, record the result from the instrument. If the concentration of water in the sample is completely unknown, it is advisable to start with a small trial portion of sample to avoid excessive titration time and depletion of the reagents. Further adjustment of the aliquot size can then be made as necessary. Replace the reagents periodically, as described in 8.4 of the written standard. For crudes too viscous to draw into a syringe, add the sample to a clean, dry dropper bottle and weigh the bottle and crude. Quickly transfer the required amount of sample to the titration cell with the dropper. Reweigh the bottle. Titrate the sample as in 12.1.2 of the written standard. When measuring the test specimen by volume, the measurement of the volume is critical. Special attention should be used in determining the test specimen volume. Take care in filling the syringe to reduce the formation of gas bubbles. The presence of gas bubbles in a syringe can be a source of interference. The tendency of the crude to form gas bubbles may be a function of the crude type and corresponding vapor pressure. Prepare the apparatus for use as described in section 10 of the written standard. Ensure the syringe is of suitable capacity. See 7.3 of the written standard. Immediately after the mixing step described in 9.6 of the written standard, withdraw at least three portions of the sample and discard to waste. Immediately withdraw a fourth portion. Wipe the needle clean, invert the syringe, and allow any bubbles in the syringe to come to the outlet. Expel the bubbles. Wipe the needle and record the volume in the syringe to the nearest 1 or 10 microliters, as appropriate. Inject the entire test specimen into the Karl Fischer reagent below the surface of the reagent in the titration cell. Inject the test specimen into the Karl Fischer reagent. After the endpoint is reached, record the results from the instrument. Prior to reporting the results, the results shall be checked against the repeatability requirement as discussed in 16.1.1 of the written standard.