Fig. 2—Detail of 100 ml Short-Neck FlaskS6.1.3 Preparation of apparatus. (a) Thoroughly clean and dry all glassware.(b) Insert thermometer through the side tube until the tip of the bulb is 6.5 mm. ( 1⁄4 inch) from the bottom center of the flask. Seal with a short piece of natural rubber, EPDM, SBR, or butyl tubing.(c) Place 60 ±1 ml. of brake fluid and the silicon carbide grains into the flask.(d) Attach the flask to the condenser. When using a heating mantle, place the mantle under the flask and support it with a ring-clamp and laboratory-type stand, holding the entire assembly in place by a clamp. When using a rheostat-controlled heater, center a standard porcelain or hard asbestos refractory, having a diameter opening 32 to 38 mm., over the heating element and mount the flask so that direct heat is applied only through the opening in the refractory. Place the assembly in an area free from drafts or other types of sudden temperature changes. Connect the cooling water inlet and outlet tubes to the condenser. Turn on the cooling water. The water supply temperature shall not exceed 28 °C. (82.4 °F.) and the temperature rise through the condenser shall not exceed 2 °C. (3.6 °F.).S6.1.4 Procedure. Apply heat to the flask so that within 10 ±2 minutes the fluid is refluxing in excess of 1 drop per second. The reflux rate shall not exceed 5 drops per second at any time. Immediately adjust the heating rate to obtain an equilibrium reflux rate of 1 to 2 drops per second over the next 5 ±2 minutes. Maintain this rate for an additional 2 minutes, taking four temperature readings at 30-second intervals. Record the average of these as the observed ERBP. If no reflux is evident when the fluid temperature reaches 260 °C (500 °F), discontinue heating and report ERBP as in excess of 260 °C (500 °F).S6.1.5 Calculation. (a) Thermometer inaccuracy. Correct the observed ERBP by applying any correction factor obtained in standardizing the thermometer.(b) Variation from standard barometric pressure. Apply the factor shown in Table III to calculate the barometric pressure correction to the ERBP.