9. Procedure
9.1 Mix the sample thoroughly, measure 25 more or less 5 mL by means of a 25-mL graduated cylinder, and transfer as much as possible of the contents of the cylinder by pouring it into the flask. Wash the graduated cylinder with successive portions of hot water until only a negligible amount of oil is left in the cylinder. Add additional water to the flask to make a total of approximately 500 mL of water. Fill the trap with cold water and add 1 more or less 0.1 mL of denatured ethanol to the water in the trap.
9.2 Assemble the apparatus as shown in Fig. 1, so that the tip of the condenser is directly over the indentation in the trap.
9.3 Apply heat to the flask at such a rate that refluxing starts within 7 to 10 min after heat is applied, with the water and sample being at 21 to 38°C prior to application of heat. After boiling and condensation has commenced, adjust the rate of boiling so that condensed distillate is discharged from the condenser at a rate of 1 to 3 drops per s. (Warning - Hot exposed surface. Avoid contact by wearing protective equipment as required.)
NOTE 3 - Bumping with a tendency to froth over is often experienced with dirty oils. The use of boiling stones, steel wool, or about 5 mL of concentrated hydrochloric acid (HCl) in the flask is often helpful in eliminating this difficulty.
9.4 Obtain readings of the amount of diluent at the following times, taken from the time that refluxing starts: 5, 15, and 30 min, more or less 1 min, and each 15 min, more or less 1 min, following until the test is complete. Completion of the test shall be determined on the basis of either or both of the following criteria:
9.4.1 The test is complete when the volume of diluent increases by not more than 0.1 mL in any 15-min period during the course of the test.
9.4.2 The test is complete when the volume of diluent obtained in a given time indicates completion, as follows:
9.5 When the test continues without reaching the limit defined in 9.4.1, to a point at which any of the conditions described in 9.4.2 are encountered, the latter shall define the completion of the test.
9.6 When the test is complete by either of the criteria defined in 9.4.1 and 9.4.2, turn off the heat. Allow the equipment to stand for at least 30 min to allow the distillate to separate completely and to cool to approximately room temperature. Read the volume of diluent collected in the trap. If the volume of diluent exceeds the calibrated capacity of the trap, discontinue the test and report the results as 20 % plus.
10. Calculation
10.1 The diluent content of the sample, expressed as volume percent, is equal to the volume of diluent in millilitres multiplied by 4.
NOTE 4 - In some cases with samples containing large amounts of diluent, equipment limitations do not permit collection and measurement of the full 5 mL of diluent even when more is present. This condition exists when the upper limit of the collected diluent is above the zero calibration mark on the trap. When it occurs, finish the test as prescribed in 9.6, read the maximum volume of diluent collected, calculate the corresponding percentage x, and report the results as x percent plus.