D4006_9 (16e1)

The precision of this test method can be affected by water droplets adhering to the surfaces in the apparatus and therefore not settling into the water trap to be measured. To minimize the problem, all apparatus must be chemically cleaned at least daily to remove surface films and debris, which hinder free drainage of water in the test apparatus. More frequent cleaning is recommended if the nature of the samples being run causes persistent contamination. To determine water on a volume basis, proceed as indicated in section 7.1.2.3 of the written standard. Add sufficient xylene to the flask. Make the total xylene volume 400 milliliters. To determine water on a mass basis, proceed as indicated in section 7.1.2.4. Add sufficient xylene to the flask to make the total xylene volume 400 milliliters. A magnetic stirrer is the most effective device to reduce bumping. Glass beads or other boiling aids, although less effective, have been found to be useful. Assemble the apparatus as shown in figure 1, making sure all connections are vapor and liquid-tight. It is recommended that glass joints not be greased. Insert a drying tube containing an indicating desiccant into the end of the container to prevent condensation of atmospheric moisture inside the condenser. Circulate water between 20 and 25 degrees Celsius through the condenser jacket. Apply heat to the flask. The type of crude oil being evaluated can significantly alter the boiling characteristics of the crude solvent mixture. Heat should be applied slowly during the initial stages of the distillation, approximately 1/2 to 1 hour, to prevent bumping and possible loss of water from the system. Condensate shall not proceed higher than 3/4 of the distance up the condenser inner tube, point A in figure 1 of the written standard. To facilitate condenser washdown, the condensate should be held as close as possible to the condenser outlet. After the initial heating, adjust the rate of boiling so that the condensate proceeds no more than 3/4 of the distance up the condenser inner tube. Distillate should discharge into the trap at a rate of approximately two to five drops per second. Continue distillation until no water is visible in any part of the apparatus-- except in the trap-- and the volume of water in the trap remains constant for at least five minutes. If there is a persistent accumulation of water droplets in the condenser inner tube, flush was xylene. A jet spray washing tube-- see figure 2 of the written standard-- or equivalent device is recommended. The addition of an oil-soluble emulsion breaker at a concentration of 1,000 PPM to the xylene wash helps dislodge the clinging water drops. After flushing, re-distill for at least five minutes. The heat must be shut off at least 15 minutes prior to washdown to prevent bumping. After washdown, apply heat slowly to prevent bumping. Repeat this procedure and no water is visible in the condenser and the volume of the water in the trap remains constant for at least five minutes. If this procedure does not dislodge the water, use the TFE fluorocarbon scraper-- pick shown in figure 2 of the written standard-- or equivalent device to cause the water to run into the trap. When the carryover of water is complete, allow the trap and contents to cool to 20 degrees Celsius. Dislodge any drops of water adhering to the sides of the trap with the TFE fluorocarbon scraper or pick, and transfer them to the water layer. Read the volume of the water in the trap. The trap is graduated in 0.05-milliliter increments, but the volume is estimated to the nearest 0.025 milliliters.