Simulated Weathering of Oils on Seawater 



The simulated weathering was performed in a 12-liter three- 

 necked flask filled to the halfway mark with 6 liters of 3% aqueous 

 sodium chloride. The apparatus is shown in Figure 6. The diameter 

 of the flask was 29 cm, and therefore the surface area of the salt 

 water was 660 sq cm. A weighed 330-ml portion of the fuel oil was 

 added to provide a 5-mm layer of oil. 



Air was supplied, at a flow of 6 liters per minute, through 

 an inlet tube reaching near the bottom of the flask. This air was 

 first freed of oil by filters and was saturated with water by a fritted 

 glass bubbler. Wind was provided by a paddle 15 cm wide and 4.5 cm 

 high, suspended above the oil layer and rotated at 600 rpm. The circum- 

 ference of the paddle was 47 cm. Since one mile per hour is 44.7 

 cm per second, one revolution per second provides a speed of about 1 

 mile per hour at the paddle tip. At 600 rpm, the wind speed at the 

 paddle tip was thus about 10 miles per hour. 



A preliminary run was made with Fuel Oil C. This run was allowed 

 to progress for 44 days, during about 15 of which the stirring motor 

 was inoperative, and no wind was produced. All the other weathering 

 experiments were run for 7 days, with wind. One exception was a second 

 weathering of Oil D which was performed without wind. 



At the completion of each run, the distillate fuel oil and the 

 water were allowed to separate for several hours. The bulk of the 

 weathered oil was then sjrphoned off through a glass tube, which was 

 inserted in one of the necks of the flask. This tube was flared at 

 the bottom and barely touched the surface of the oil. A slight vacuum 

 was used to lift the oil out of the flask and transfer it into a weighed 

 bottle. The bulk of the salt water was then removed from the flask 

 through the air inlet tube. A vacuum was applied, and the salt water 

 was collected in a filter flask. The remainder of the oil and water 

 was mixed with hexane, and the resulting hexane solution was washed 

 with water and evaporated. The evaporation of the hexane was completed 

 by placing the flask containing the oil into a water bath at 80°C 

 and passing 400 ml per minute of dry nitrogen through the oil for 1 

 hour after escaping vapors of hexane were no longer visible. 



The weathered NSFO did not coalesce well and could not be syphoned 

 off. It was recovered by decanting repeatedly over a period of several 

 days until no more salt water separated. The residual oil and water 

 mixtures were extracted with dichloromethane , and the dichlorome thane 

 solution was washed and evaporated in the water bath imder nitrogen 

 flow. 



The amounts of original and recovered oil are shown in Table 3. 



The weathered distillate fuels were subjected to gas chromatography 

 under the same conditions described above (under Properties of Fuel Oils) 

 The chromatograms obtained for the four fuel oils after 1 week of 

 weathering with wind are shown in Figures lb, 2b, 3b and 4b. 



