KCl, NaCl solution conductivity

Krassi

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Apr 16, 2002, 7:47:26 AM4/16/02

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Hi,
I want to obtain a KCl or NaCl water solution with a conductivity 250
uS/cm. How do you think, is there any relation between concentration
and conductivity and how can I calculate this relation. I tried to
obtain this with the program CurveExpert, but results are bad.
Can anybody help.
Thanks in advance
Krassi

Anon

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Apr 16, 2002, 9:40:52 AM4/16/02

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"Krassi" <ktar...@yahoo.com> wrote in message
news:86dcb088.02041...@posting.google.com...

I know that the conductivity of 0.05 M KCl is 6660 uS and 0.01 M KCl is 1414
uS

Repeating Decimal

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Apr 16, 2002, 4:35:54 PM4/16/02

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in article 86dcb088.02041...@posting.google.com, Krassi at
ktar...@yahoo.com wrote on 4/16/02 4:47 AM:

I recently bought a Corning CD30 conductivity meter for use in my
greenhouse. I cost about $60. It seems to have the proper conductivity range
for you. It came with calibration solutions. With it, you should be able to
make candidate solutions and measure them. Then calculate how much salt or
water you need to get your desired conductivity. Do that and recheck your
conductivity.

Bill

Krassi

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Apr 16, 2002, 9:36:44 PM4/16/02

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I made solutions with different concentrations, measured their
conductivity with a conductivimeter and entered the values in the
program CurveExpert to obtain the polinomial curve. The program is
very good, but for conductivities range uS/cm the results are bad.
Probably there is some other factor that changes
conductivity/concentration dependance for low concentrations?!?

Krassi

Lasse Murtomäki

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Apr 18, 2002, 4:32:45 AM4/18/02

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Molar ionic conductivities at inifinite dilution:

K+: 73.50 Scm^2/mol
Na+: 50.10 Scm^2/mol
Cl-: 76.35 Scm^2/mol

For example KCl:

250 uS/cm = [KCl]*(73.50 + 76.35) Scm^2/mol

[KCl] = 1.668e-6 mol/cm^3 = 1.668 mM = 0.124 g/l

The solution is so dilute that the molar ionic conductivities at inifinite
dilution can be used without error being too large.

Kohlrausch law is said to be valid for strong electrolytes, like KCl or
NaCl, i.e. the molar conductivity of salt would decrease as a fuction of the
square root of the concentration:

L = L0 - K*sqrt(C)

but actually such a plot is not a very good straight line. (I took the
conductance data from CRC Handbook of Chemistry and Physics).
--
Lasse Murtomäki
Helsinki University of Technology
Lab. Phys. Chem. Electrochem.
lasse.m...@hut.fi

Nick Jancewicz

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Apr 19, 2002, 9:18:42 PM4/19/02

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You didn't say what temperature you were performing your measurements at. If it
deviates
much from 25C then maybe your conductivity meter is using the wrong
temperature-compensation
algorithm? The commonly used NaCl temperature-compensation algorithm (2%/degree
C) is only a
"rule of thumb" so some conductivity meters allow users to select a
temperature-compensation
method that is better-suited for the specific ions of the solution they are
dealing with. Or
perhaps your meter is reading out in temperature-uncompensated units of measure?
When was
your conductivity measurement probe last calibrated? The condition of the probe
can be a large
source of error depending on what it was last being used to measure.

Nick

"Krassi" <ktar...@yahoo.com> wrote in message
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suja...@gmail.com

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Oct 27, 2016, 3:08:39 AM10/27/16

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In the low concentration, the conductivity value donated by water to dissolve the salt is more significant. That is way, we can't conclude concentration vs conductivity. Furthermore, carbon dioxide in the environment is another factor that contribute in the conductivity measurement especially for low value.

Sujarwo (Jakarta)