hydrocarbons as well as with aqueous solvent systems. Some of the more fre- 

 quently encountered chemicals in this group include ethyl alcohol, isopropyl 

 alcohol, ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, 

 ethylene glycol monobutyl ether, and diethyl ene glycol monomethyl ether. 

 The more volatile members of the group are quite flammable. 



Water 



This solvent is the least toxic, least hazardous, and most economical 

 of the solvents. It lacks solubility or miscibility with oils. When water 

 is used as the solvent, special problems exist in the choice of surface-active 

 agents and other additives in order to provide the necessary miscibility with 

 oils. Glycols and alcohol are used to aid in miscibility. There is also 

 a problem with freezing point depression when water is used. 



ADDITIVES— STABILIZERS 



Additives are the third major component in dispersants. They are used 

 to adjust pH, inhibit corrosion, increase hard water stability, fix emulsion 

 once it is formed, and adjust color and appearance. 



DISPERSANT USE 



GENERAL 



Dispersants theoretically serve to increase the surface area of an oil 

 slick and to disperse oil globules throughout the larger volume of water, 

 thereby aiding in accelerated degradation of oils by microbiological means. 

 The chemical dispersants do not themselves destroy oil. They vary consider- 

 ably in toxicity, effectiveness, and ability to stabilize the oil after extended 

 periods of time (Figure 1). Technology for proper application of dispersants 

 over large oil slicks with necessary mixing is currently lacking. Use appears 

 far more critical in harbor and estuarine areas and in proximity to shore. 

 Particular care must be exercised where water supply might be affected. The 

 desirability of employing dispersants in the open sea remains unresolved, 

 although their use in the ocean is potentially more promising, pending addi- 

 tional field data. After widespread dispersant use during major incidents, 

 reports led to the conclusion that dispersant-oil mixture caused more damage 

 to aquatic life than the oil alone. For beaches, they actually compounded 

 the problem by adding the amount of pollutants present, by causing the oil 

 to penetrate more deeply into the sand, and by disturbing the compactness 

 of the sand, so as to increase beach erosion through tidal wave action. 



TOXICITY 



Current information indicates that dispersants vary considerably in 

 toxicity. The combination of oil and dispersant may increase the toxicity 

 of either the oil, the dispersant chemical, or both. The possibility of this 

 "synergistic" action must be carefully examined before wholesale application 

 of such a product is permitted. Dispersing of the oil, which has toxic com- 

 ponents, may also compound the damage. Some examples of the toxicity of 40 

 older dispersants (Portmann 1970) are shown in Table 1. It is important to 



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