The drop-weight test is an improved interfacial tension method for predicting the relative effectiveness of oil-spill dispersant products. The test is based on the relationship between the weight of a drop of oil detached from a capillary beneath a dispersant-in-seawater solution and the lowering of the interfacial tension between oil and water. A modified test procedure, based on measuring the time for a drop detachment rather than the weight, significantly reduces the test time and simplifies the apparatus. Another modification permits the determination of relative diffusion rates of dispersants through an oil column. Seventeen water-based dispersant products were evaluated with light Arabian crude oil and, in some cases, with no. 6 fuel oil using the modified procedures. The results were interpreted in terms of data reliability and compared with information obtained by the Standard EPA Dispersant Effectiveness Test (the EPA test) (McCarthy et al., 1973).

We have evaluated a number of laboratory tests of dispersant effectiveness using commercial oil spill products and No. 2 and No. 6 fuel oils. The tests-the EPA, Mackay/Steelman, Russian, French, Warren Spring, and an interfacial tension method developed at SRI-are reviewed in terms of type, scale, method of applying mixing energy, and the time required to conduct a product evaluation. The experimental results, compared in terms of the precision of the test data and the effectiveness ranking order of the six nonionic dispersants, demonstrate that the relative effectiveness found for the dispersants varies appreciably as a function of the testing method. Reasons for the variations are discussed and recommendations are presented on how to achieve dispersant testing data that are more representative of real-world conditions. Of the six testing methods evaluated, the EPA, Mackay/Steelman, and the interfacial tension methods are the most amenable to improvement.

Thick films of high-temperature superconductors have been deposited electrophoretically using techniques developed for office copier toning. The resultant films are dense because of the high charge density per particle and the high fields during deposition. Orientation by electrostatic and magnetic fields has been demonstrated.