From: tkoenig@netcologne.de   
      
   Hi,   
      
   It is a well-known effect that when an "insulating" liquid (electric   
   conductivity of less than 50 * 10^(-12) S/m) flows through a metal,   
   grounded pipe, charge separation can occur, and the liquid at the   
   outlet of the pipe then carries an electrostatic charge.   
      
   This can be quite relevant because such liquids are also often   
   flammable, and their vapors can form explosive mixtures with air,   
   which can be ignited by the electrostatic charge, with literally   
   catastrophic results.   
      
   I have found a qualitative explanation of the effect of charge   
   accumulation in the book "Static Electricity" by Lüttgens et al.   
   (which you can find with Google books if you're interested)   
   in chapter 2.5, but the authors do not cite any sources, and no   
   quantitative relationships for charging of the liquid depending   
   on material parameters, flow characteristics and so on.   
      
   Has quantitative work been done on this?  Given the large   
   significance of the problem, I would expect something, but so   
   far I have not been able to find a lot.   
      
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