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NOTE: To get off this list, send email to majordomo@aqua.ccwr.ac.za with the body of the message containing the line: unsubscribe sowacs Dear Fernando: Measuring the resistivity of water is what one does when one measures the electrical conductivity of water. I suggest you look at a physical chemistry textbook for the methods of measuring electrical conductivity of a water sample. What follows is a quote from text written by Bower and Wilcox in ASA monograph #9 published in 1965: the basic principles haven't changed in the meantime. " The determination of electrical conductivity is made by measuring the electrical resistance between parallel electrodes immersed in the solution or extract. In such a system, --- when alternating current is applied (JDO, Aug 28) ---the solution between the electrodes becomes an electrical conductor to which the physical lows relating the resistance are applicable. The electrical resistance R is directly proportional to the distance L between the electrodes and inversely proportional to the cross-sectional are A of the conductor. Thus R = rL/A, where r is a proportionality constant known as the electrical resistivity, the value of which depends on the nature of the conductor." At 06:38 PM 8/28/01 +0000, you wrote: > >Dear Fernando, > >I do not know anyone who have measured the resistivity of water only but I >know some people who have done plenty of resistivity measurements on rock >cores with different saturations. If you think this may be a start, please >email me at M.Pokar@earth.leeds.ac.uk > >Maggie > > > >From: owner-sowacs@aqua.ccwr.ac.za > >Subject: Resistivity of water > >Date: Wed, 22 Aug 2001 20:01:47 GMT > > > >Hello, I am a student from Brasil, and I'd like to know how to prepare > >a cell to measure the resistivity of water. > >Can I use a glass cell with copper electrodes? > >Best regards, > > Fernando Martins > > > >[Bruce comments > >Fernanado > >I'm sure there will be someone on the list who will provide a good general > >introduction to measuring the resistivity of water. > > > >On sowacs, there is currently only information on measuring the EC of the > >soil water solution. > > > >For a discussion on unsaturated soil sampling, see the > >This is a compendium of replies on the feature page: > >http://www.sowacs.com/feature/unsatsampling.html > > > >To measure the conductivity of mud see : > >http://www.sowacs.com/archives/99-11/msg00005.html > > > >For a more detailed example of a sensor look at : > >http://www.sowacs.com/feature/deltat/sigmaprobe.html > >and the theory at > >http://www.sowacs.com/feature/deltat/ec1theory.html > > > >Bruce] > > J.D. (Jim) Oster POB 1344 Graeagle, Ca 96103 530.836.1835 Lnd Line 909.224.6785 Cell Ph Website esce.ucr.edu