Re: Resistivity of water

[Dardo]

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Dear Fernando,

I wish to add that stainless steel electrodes will performs better than
copper electrodes. The alternating current could be sinusoidal of 2000 Hz
aproximately. If high quality measurements are requiered you will need
platinum electrodes.

Dardo

At 06:10 AM 29/08/01 GMT, you wrote:
>
>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
>
>
>
>
Prof. Dardo Oscar Guaraglia
Facultad de Ingenieria
Universidad Nacional de La Plata