Components of the oil that are dispersed into water will become more 

 volatile because their vapor pressure is effectively augmented by that of 

 the water, and a ''steam distillation'' will occur. Similarly, the presence 

 of water should effectively augment the vapor pressure of the bulk oil 

 and speed its evaporation, especially where there is a turbulent interface. 



The salt water extracts from the simulated weathering experiments 

 contained 14.5 to 37 ppm of organic carbon, as shown in Table 6, and thus 

 about 17 to 44 ppm of organic compounds. These are higher concentrations 

 than expected on the basis of the literature quoted above , but lower 

 concentrations than obtained in two unpublished investigations. Because 

 the salt water extracts were very clear, it is doubtful that the increased 

 organic content was due to dispersed material. It is more likely that 

 the increased organic content was due to the presence of oxygenated 

 organic compounds that might have been formed by the aeration of the 

 fuel oils. The total dissolved organic compounds, extracted from the 

 330-ml portions of the oils by the 6 -liter portions of salt water (a 

 ratio of 1:18), constituted 0.037% to 0.093% of the original oils. 

 These figures are very close to the 0.053% of dissolved oil that Smith and 

 Maclntyre found in their weathering of 30 ml of No. 2 fuel oil in contact 

 with 10 liters of salt water (a ratio of 1:333) [2]. 



Changes in Viscosity 



The viscosity changes of the Navy distillate fuels in the 

 simulated weathering were not very great. The values in centistokes 

 increased by a maximum of 45%, as shown in Table 5. This change is 

 equivalent to the change obtained when the temperature of the oils is 

 lowered from about 220C to 10°C (or from about 70°F to 50°F) . This is 

 the temperature change that would give the same increases in viscosity 

 according to graphs on standard viscosity-temperature charts [11]. An 

 oil evaporated to the same extent at sea might pick up foreign matter, 

 and the viscosity might thus increase somewhat further. 



Navy special fuel oil exposed to the same simulated weathering gave 

 very different results. These differences apparently were caused by the 

 greater viscosity of the NSFO, by its greater density, and probably by 

 the presence of more polar constituents. The agitation of the NSFO was 

 not as effective. A thick emulsion of NSFO and salt water was formed 

 which broke into clumps but did not form very small particles in the 

 salt water. When the aeration was stopped, this ''mousse'' formed a 

 layer about 30 mm thick and did not change in thickness for four days. 

 The distillate fuels, on the other hand, had separated and coalesced 

 rapidly. 



The results with the NSFO are not as reliable as those with the 

 distillate fuels because of experimental difficulties. About half of 

 the evaporated NSFO was recovered by decanting and the remainder by 

 extraction with dichlorome thane and subsequent evaporation. However, 

 there were lonavoidable losses and the residue was probably greater than 

 the indicated 92%. The viscosities of the NSFO could be measured only 



11 



