ASTM D483 Test Method for Unsulfonated Residue of Petroleum Plant Spray Oils
11. Procedure
11.1 Adjust the temperature of the boiling water bath to 99.5 to 100°C and keep it in this temperature range throughout the test. Adjust the shaker rate and check it before and after each test to make sure that the rate does not deviate more than ±10 cycles/min from the rate established by calibration. (Warning - When hand shaking, protect the face with a safety mask and point the Babcock bottle away from other personnel. Protect hands by wearing suitable safety gloves.)
NOTE 1 - If hand shaking is used, shake the sulfonation flask by grasping the neck between the thumb and index finger and swinging the flask through an arc of approximately 20° so that the bottom of the flask passes through a distance of 64 to 89 mm. Shake at the rate established by calibration within a tolerance of ±10 cycles/min.
11.2 Using Test Methods D1298 or D4052, determine the density at 25°C in grams per millilitre by means of data obtained from Vol VIII and Vol XI/XII of the Petroleum Measurement Tables. (See Guide D1250.)
11.3 Weigh into a clean, dry sulfonation flask the equivalent of 4.9 to 5.1 mL of the sample at 25°C, weighed to the nearest 0.005 g, adding the oil to the flask by pipet, and taking care to deposit as little oil as possible on the neck of the flask. From the weight of the sample, calculate its volume at 25°C.
11.4 Slowly introduce 20 ± 0.5 mL of H2SO4 (98.61 %) into the flask in such a way that oil adhering to the neck of the flask will be washed down. Transfer the flask to the carrier, and suspend the carrier in the boiling water bath, with the flask immersed to a point between the 0 and 10 marks, noting the time when this is done. Close the cover of the bath, and direct a gentle stream of air across the top of the flask to blow away any steam arising from the opening.
11.5 After the flask has been in the bath for 10 ± 1 min, remove the carrier and install it, with minimum delay, on the shaker. While wearing a face shield, shake for 10 ± 1 s at the rate established in the calibration with the reference spray oil. (Warning - Certain samples of low unsulfonated residue can foam excessively when shaken. Stop the shaker when the foam rises in the neck of the flask, and shake intermittently but at the specified rate. Substitute the counter for the timer and shake a total number of cycles equal to one-sixth of the number representing the established rate in cycles per minute, even though it requires more than 10 s for example, if the rate is 425 cycles/min, shake 71 cycles.) After shaking, return the carrier to the bath as quickly as possible. Repeat the shaking at 10 ± 1 min intervals for a total of six shaking periods, so that an hour has elapsed between the time of placing the flask in the bath, and the removal for the final shaking.
11.6 After the final shaking, cool to approximately room temperature, and add sufficient H2SO4 (95 %) to raise the oil into the neck of the flask nearly to the top graduation. Place the flask in the centrifuge, balancing as necessary, and centrifuge for 10 min at a speed calculated by the equation given in A1.1.6, or taken from Table 1 to give a relative centrifugal force between 80 and 100 at the bottom of the flask. Transfer the flask to a water bath maintained at 25 ± 0.5°C for 10 ± 1 min, with the graduated neck immersed to the upper oil level.
NOTE 2 - The use of rubber cushions in the centrifuge carrier tubes to avoid breakage is recommended.
11.7 Transfer the flask to the shelf in the 25°C bath. Using a suitable light source, and the aid of a viewing lens, record the reading on the graduated neck at the top and bottom of the oil column, estimating to one fifth of the smallest division. The bottom reading is generally sharp and straight across, and offers no problem. In reading the top, hold a black strip (about 10 by 50 mm) at the back of the neck, and about 5 mm below the top of the oil column, which makes the lowest meniscus appear as a black curve. Install the viewing lens at a right angle to the neck of the flask at the proper height, focus it, and read the lowest black meniscus. The upper and lower levels on the oil layer are represented by points A and B in Fig. 1. Point A denotes the lowest portion of the boundary between the clear oil and the darkest part of the air-liquid interface, and point B refers to the lowest portion of the interface between the clear oil and sulfonation acid.
11.8 Repeat the centrifuging and temperature equilibration (11.6 and 11.7), until constant readings have been obtained.
