Although the basis of the conductivity ratio is the conductivity of a defined KCl solution, in practice it is necessary to use a seawater calibrated against the KCl standard. (ie IAPSO standard Seawater).

Therefore, the primary standard for Practical Salinity is the defined KCl solution and the transfer standard is IAPSO Standard Seawater which is prepared only by OSIL . OSIL are ISO9002 accredited for the preparation and calibration of salinity standards, therefore all the measurements of mass, resistance and temperature are traceable to national and international standards.

It is worth noting that when the Practical Salinity Scale was introduced in 1978 the link with chlorinity was broken and salinity became a dimensionless quantity thereby eliminating any units (part per thousand etc.). The more recently introduced PSU (Practical Salinity Unit) is also invalid.

Also, all temperature measurements on the Practical Salinity Scale were made on the International Practical Temperature Scale of 1968 (IPTS68) and this remains even though a new international temperature scale was introduced in January 1990 (ITS90). There is some argument that the current definition of salinity should be changed to reflect the new temperature scale and even though the equations have been calculated by scientists from OSIL and one or two institutes, this remains unimplemented.