The electrical conductivity of weight diluted and concentrated standard seawater as a function of salinity and temperature

Abstract

The ratios <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_{s,t,o}</tex> of electrical conductivity of seawater samples of precisely known salinity to standard seawater at the same temperature have been measured over a wide range of salinities from 0 to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">42\permil</tex> S and over the full range of oceanic temperatures from -2 to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">35\deg</tex> C. The samples with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S&lt;35\permil</tex> were prepared by accurate weight dilution of standard seawater with distilled water. High salinity samples were prepared by fast evaporation of standard seawater and subsequent weight dilution into the already determined < <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">35\permil</tex> range. An equation was derived which expresses the S versus <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_{s,t,o}</tex> relationship very precisely from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-42\permil</tex> and at all temperatures, i.e., <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S = f_{1}(R_{s,t,o}) + f_{2}(R_{s, t,o},t) =\Sigma_{n=0}^{5} a_{n}R^{n/2}+ \frac{\Delta t}{1+k\Delta t} \Sigma_{n=0}^{5} b_{n}R^{n/2}</tex> where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Delta t = t-15\deg</tex> C, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R = R_{s, t.o}</tex> ; only the first term <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f_{1}</tex> is required at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15\deg</tex> C. The effeet of temperature on the electrical conductivity of standard seawater was also measured. The ratio <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r_{t}</tex> of the conductivity at temperature <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</tex> to the conductivity at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15\deg</tex> C ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C_{35,t, o}/C_{35,15,o}</tex> ) is very aeenrately expressed by a fourth degree equation in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</tex> . i.e, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r_{t}=\Sigma_{n=0}^{4} c_{n}t^{n}</tex> These two equations are sufficient for all salinity determinations at normal atmospheric pressure.