Salinity bench salinometers

In the early 1960s, bench salinometers were developed that allowed measurement of the electrical conductivity of a seawater sample relative to that of a standard with high precision. Cox et al. (1967) had related chlorinity and conductivity ratios of seawater to standard seawater at temperatures higher than 10 °C and tabulated their results (UNESCO, 1966). Following their work, the responsible international oceanographic organizations adopted a redefinition of salinity (Wooster et al, 1969). Firstly, it was assumed that salinity was proportional to chlorinity, to be consistent with the assumed constancy of the ionic composition. The constant was chosen so that for 5=35 %o, both the Knudsen formula (3-1) and the new relationship... 

The 1969 definition and the available corrections for temperatures higher than 10 °C were suitable for use with bench salinometers. However, for use with in situ measuring systems, it was insufficient because it did not cover the whole oceanic range of parameters. It was this severe lack of validity and the demand to define salinity solely from physical parameters that led to the definition of the Practical Salinity Scale of 1978. 

To determine salinity from bottle samples, bench salinometers have now replaced the chlorinity titration method almost completely, initially for practical reasons. Subsequently, as the 1978 Practical Salinity Scale has been adopted, consistent application of this scale requires the use of salinometers. 

Only lAPSO recognized SSW provides a reliable standard for conductivity ratio measurements. It should be used to standardize each bench salinometer before being used for sample salinity measurements and to detect and eventually trace any drift. The use of so-called substandards for standardization is not recommended, as it will significantly decrease accuracy (see Section 3.5.7 for exceptions if a decrease in accuracy is acceptable). 

All bench salinometers must be standardized with SSW. While strongly diseouraged for achieving WOCE standards in salinity, substandards may be used together with SSW to control the stability of the salinometer if less than the best aehievable accuracy is acceptable in... 

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